Enum Option

pub enum Option<T> {
    None,
    Some(T),
}

Available on crate feature dep_bytemuck only.

The Option type. See the module level documentation for more.

Variants

None

No value.

Some(T)

Some value of type T.

Implementations

impl<T> Option<T>

pub const fn is_some(&self) -> bool

Returns true if the option is a Some value.

Examples

let x: Option<u32> = Some(2);
assert_eq!(x.is_some(), true);

let x: Option<u32> = None;
assert_eq!(x.is_some(), false);

pub fn is_some_and(self, f: impl FnOnce(T) -> bool) -> bool

Returns true if the option is a Some and the value inside of it matches a predicate.

Examples

let x: Option<u32> = Some(2);
assert_eq!(x.is_some_and(|x| x > 1), true);

let x: Option<u32> = Some(0);
assert_eq!(x.is_some_and(|x| x > 1), false);

let x: Option<u32> = None;
assert_eq!(x.is_some_and(|x| x > 1), false);

pub const fn is_none(&self) -> bool

Returns true if the option is a None value.

Examples

let x: Option<u32> = Some(2);
assert_eq!(x.is_none(), false);

let x: Option<u32> = None;
assert_eq!(x.is_none(), true);

pub fn is_none_or(self, f: impl FnOnce(T) -> bool) -> bool

Returns true if the option is a None or the value inside of it matches a predicate.

Examples

let x: Option<u32> = Some(2);
assert_eq!(x.is_none_or(|x| x > 1), true);

let x: Option<u32> = Some(0);
assert_eq!(x.is_none_or(|x| x > 1), false);

let x: Option<u32> = None;
assert_eq!(x.is_none_or(|x| x > 1), true);

pub const fn as_ref(&self) -> Option<&T>

Converts from &Option<T> to Option<&T>.

Examples

Calculates the length of an Option<String> as an Option<usize> without moving the String. The map method takes the self argument by value, consuming the original, so this technique uses as_ref to first take an Option to a reference to the value inside the original.

let text: Option<String> = Some("Hello, world!".to_string());
// First, cast `Option<String>` to `Option<&String>` with `as_ref`,
// then consume *that* with `map`, leaving `text` on the stack.
let text_length: Option<usize> = text.as_ref().map(|s| s.len());
println!("still can print text: {text:?}");

pub const fn as_mut(&mut self) -> Option<&mut T>

Converts from &mut Option<T> to Option<&mut T>.

Examples

let mut x = Some(2);
match x.as_mut() {
    Some(v) => *v = 42,
    None => {},
}
assert_eq!(x, Some(42));

pub const fn as_pin_ref(self: Pin<&Option<T>>) -> Option<Pin<&T>>

Converts from Pin<&Option<T>> to Option<Pin<&T>>.

pub const fn as_pin_mut(self: Pin<&mut Option<T>>) -> Option<Pin<&mut T>>

Converts from Pin<&mut Option<T>> to Option<Pin<&mut T>>.

pub const fn as_slice(&self) -> &[T]

Returns a slice of the contained value, if any. If this is None, an empty slice is returned. This can be useful to have a single type of iterator over an Option or slice.

Note: Should you have an Option<&T> and wish to get a slice of T, you can unpack it via opt.map_or(&[], std::slice::from_ref).

Examples

assert_eq!(
    [Some(1234).as_slice(), None.as_slice()],
    [&[1234][..], &[][..]],
);

The inverse of this function is (discounting borrowing) [_]::first:

for i in [Some(1234_u16), None] {
    assert_eq!(i.as_ref(), i.as_slice().first());
}

pub const fn as_mut_slice(&mut self) -> &mut [T]

Returns a mutable slice of the contained value, if any. If this is None, an empty slice is returned. This can be useful to have a single type of iterator over an Option or slice.

Note: Should you have an Option<&mut T> instead of a &mut Option<T>, which this method takes, you can obtain a mutable slice via opt.map_or(&mut [], std::slice::from_mut).

Examples

assert_eq!(
    [Some(1234).as_mut_slice(), None.as_mut_slice()],
    [&mut [1234][..], &mut [][..]],
);

The result is a mutable slice of zero or one items that points into our original Option:

let mut x = Some(1234);
x.as_mut_slice()[0] += 1;
assert_eq!(x, Some(1235));

The inverse of this method (discounting borrowing) is [_]::first_mut:

assert_eq!(Some(123).as_mut_slice().first_mut(), Some(&mut 123))

pub const fn expect(self, msg: &str) -> T

Returns the contained Some value, consuming the self value.

Panics

Panics if the value is a None with a custom panic message provided by msg.

Examples

let x = Some("value");
assert_eq!(x.expect("fruits are healthy"), "value");

let x: Option<&str> = None;
x.expect("fruits are healthy"); // panics with `fruits are healthy`

Recommended Message Style

We recommend that expect messages are used to describe the reason you expect the Option should be Some.

let item = slice.get(0)
    .expect("slice should not be empty");

Hint: If you’re having trouble remembering how to phrase expect error messages remember to focus on the word “should” as in “env variable should be set by blah” or “the given binary should be available and executable by the current user”.

For more detail on expect message styles and the reasoning behind our recommendation please refer to the section on “Common Message Styles” in the std::error module docs.

pub const fn unwrap(self) -> T

Returns the contained Some value, consuming the self value.

Because this function may panic, its use is generally discouraged. Panics are meant for unrecoverable errors, and may abort the entire program.

Instead, prefer to use pattern matching and handle the None case explicitly, or call unwrap_or, unwrap_or_else, or unwrap_or_default. In functions returning Option, you can use the ? (try) operator.

Panics

Panics if the self value equals None.

Examples

let x = Some("air");
assert_eq!(x.unwrap(), "air");

let x: Option<&str> = None;
assert_eq!(x.unwrap(), "air"); // fails

pub fn unwrap_or(self, default: T) -> T

Returns the contained Some value or a provided default.

Arguments passed to unwrap_or are eagerly evaluated; if you are passing the result of a function call, it is recommended to use unwrap_or_else, which is lazily evaluated.

Examples

assert_eq!(Some("car").unwrap_or("bike"), "car");
assert_eq!(None.unwrap_or("bike"), "bike");

pub fn unwrap_or_else<F>(self, f: F) -> T

where F: FnOnce() -> T,

Returns the contained Some value or computes it from a closure.

Examples

let k = 10;
assert_eq!(Some(4).unwrap_or_else(|| 2 * k), 4);
assert_eq!(None.unwrap_or_else(|| 2 * k), 20);

pub fn unwrap_or_default(self) -> T

where T: Default,

Returns the contained Some value or a default.

Consumes the self argument then, if Some, returns the contained value, otherwise if None, returns the default value for that type.

Examples

let x: Option<u32> = None;
let y: Option<u32> = Some(12);

assert_eq!(x.unwrap_or_default(), 0);
assert_eq!(y.unwrap_or_default(), 12);

pub const unsafe fn unwrap_unchecked(self) -> T

Returns the contained Some value, consuming the self value, without checking that the value is not None.

Safety

Calling this method on None is undefined behavior.

Examples

let x = Some("air");
assert_eq!(unsafe { x.unwrap_unchecked() }, "air");

let x: Option<&str> = None;
assert_eq!(unsafe { x.unwrap_unchecked() }, "air"); // Undefined behavior!

pub fn map<U, F>(self, f: F) -> Option<U>

where F: FnOnce(T) -> U,

Maps an Option<T> to Option<U> by applying a function to a contained value (if Some) or returns None (if None).

Examples

Calculates the length of an Option<String> as an Option<usize>, consuming the original:

let maybe_some_string = Some(String::from("Hello, World!"));
// `Option::map` takes self *by value*, consuming `maybe_some_string`
let maybe_some_len = maybe_some_string.map(|s| s.len());
assert_eq!(maybe_some_len, Some(13));

let x: Option<&str> = None;
assert_eq!(x.map(|s| s.len()), None);

pub fn inspect<F>(self, f: F) -> Option<T>

where F: FnOnce(&T),

Calls a function with a reference to the contained value if Some.

Returns the original option.

Examples

let list = vec![1, 2, 3];

// prints "got: 2"
let x = list
    .get(1)
    .inspect(|x| println!("got: {x}"))
    .expect("list should be long enough");

// prints nothing
list.get(5).inspect(|x| println!("got: {x}"));

pub fn map_or<U, F>(self, default: U, f: F) -> U

where F: FnOnce(T) -> U,

Returns the provided default result (if none), or applies a function to the contained value (if any).

Arguments passed to map_or are eagerly evaluated; if you are passing the result of a function call, it is recommended to use map_or_else, which is lazily evaluated.

Examples

let x = Some("foo");
assert_eq!(x.map_or(42, |v| v.len()), 3);

let x: Option<&str> = None;
assert_eq!(x.map_or(42, |v| v.len()), 42);

pub fn map_or_else<U, D, F>(self, default: D, f: F) -> U

where D: FnOnce() -> U, F: FnOnce(T) -> U,

Computes a default function result (if none), or applies a different function to the contained value (if any).

Basic examples

let k = 21;

let x = Some("foo");
assert_eq!(x.map_or_else(|| 2 * k, |v| v.len()), 3);

let x: Option<&str> = None;
assert_eq!(x.map_or_else(|| 2 * k, |v| v.len()), 42);

Handling a Result-based fallback

A somewhat common occurrence when dealing with optional values in combination with Result<T, E> is the case where one wants to invoke a fallible fallback if the option is not present. This example parses a command line argument (if present), or the contents of a file to an integer. However, unlike accessing the command line argument, reading the file is fallible, so it must be wrapped with Ok.

let v: u64 = std::env::args()
   .nth(1)
   .map_or_else(|| std::fs::read_to_string("/etc/someconfig.conf"), Ok)?
   .parse()?;

pub fn ok_or<E>(self, err: E) -> Result<T, E>

Transforms the Option<T> into a Result<T, E>, mapping Some(v) to Ok(v) and None to Err(err).

Arguments passed to ok_or are eagerly evaluated; if you are passing the result of a function call, it is recommended to use ok_or_else, which is lazily evaluated.

Examples

let x = Some("foo");
assert_eq!(x.ok_or(0), Ok("foo"));

let x: Option<&str> = None;
assert_eq!(x.ok_or(0), Err(0));

pub fn ok_or_else<E, F>(self, err: F) -> Result<T, E>

where F: FnOnce() -> E,

Transforms the Option<T> into a Result<T, E>, mapping Some(v) to Ok(v) and None to Err(err()).

Examples

let x = Some("foo");
assert_eq!(x.ok_or_else(|| 0), Ok("foo"));

let x: Option<&str> = None;
assert_eq!(x.ok_or_else(|| 0), Err(0));

pub fn as_deref(&self) -> Option<&<T as Deref>::Target>

where T: Deref,

Converts from Option<T> (or &Option<T>) to Option<&T::Target>.

Leaves the original Option in-place, creating a new one with a reference to the original one, additionally coercing the contents via Deref.

Examples

let x: Option<String> = Some("hey".to_owned());
assert_eq!(x.as_deref(), Some("hey"));

let x: Option<String> = None;
assert_eq!(x.as_deref(), None);

pub fn as_deref_mut(&mut self) -> Option<&mut <T as Deref>::Target>

where T: DerefMut,

Converts from Option<T> (or &mut Option<T>) to Option<&mut T::Target>.

Leaves the original Option in-place, creating a new one containing a mutable reference to the inner type’s Deref::Target type.

Examples

let mut x: Option<String> = Some("hey".to_owned());
assert_eq!(x.as_deref_mut().map(|x| {
    x.make_ascii_uppercase();
    x
}), Some("HEY".to_owned().as_mut_str()));

pub fn iter(&self) -> Iter<'_, T>

Returns an iterator over the possibly contained value.

Examples

let x = Some(4);
assert_eq!(x.iter().next(), Some(&4));

let x: Option<u32> = None;
assert_eq!(x.iter().next(), None);

pub fn iter_mut(&mut self) -> IterMut<'_, T>

Returns a mutable iterator over the possibly contained value.

Examples

let mut x = Some(4);
match x.iter_mut().next() {
    Some(v) => *v = 42,
    None => {},
}
assert_eq!(x, Some(42));

let mut x: Option<u32> = None;
assert_eq!(x.iter_mut().next(), None);

pub fn and<U>(self, optb: Option<U>) -> Option<U>

Returns None if the option is None, otherwise returns optb.

Arguments passed to and are eagerly evaluated; if you are passing the result of a function call, it is recommended to use and_then, which is lazily evaluated.

Examples

let x = Some(2);
let y: Option<&str> = None;
assert_eq!(x.and(y), None);

let x: Option<u32> = None;
let y = Some("foo");
assert_eq!(x.and(y), None);

let x = Some(2);
let y = Some("foo");
assert_eq!(x.and(y), Some("foo"));

let x: Option<u32> = None;
let y: Option<&str> = None;
assert_eq!(x.and(y), None);

pub fn and_then<U, F>(self, f: F) -> Option<U>

where F: FnOnce(T) -> Option<U>,

Returns None if the option is None, otherwise calls f with the wrapped value and returns the result.

Some languages call this operation flatmap.

Examples

fn sq_then_to_string(x: u32) -> Option<String> {
    x.checked_mul(x).map(|sq| sq.to_string())
}

assert_eq!(Some(2).and_then(sq_then_to_string), Some(4.to_string()));
assert_eq!(Some(1_000_000).and_then(sq_then_to_string), None); // overflowed!
assert_eq!(None.and_then(sq_then_to_string), None);

Often used to chain fallible operations that may return None.

let arr_2d = [["A0", "A1"], ["B0", "B1"]];

let item_0_1 = arr_2d.get(0).and_then(|row| row.get(1));
assert_eq!(item_0_1, Some(&"A1"));

let item_2_0 = arr_2d.get(2).and_then(|row| row.get(0));
assert_eq!(item_2_0, None);

pub fn filter<P>(self, predicate: P) -> Option<T>

where P: FnOnce(&T) -> bool,

Returns None if the option is None, otherwise calls predicate with the wrapped value and returns:

• Some(t) if predicate returns true (where t is the wrapped value), and
• None if predicate returns false.

This function works similar to Iterator::filter(). You can imagine the Option<T> being an iterator over one or zero elements. filter() lets you decide which elements to keep.

Examples

fn is_even(n: &i32) -> bool {
    n % 2 == 0
}

assert_eq!(None.filter(is_even), None);
assert_eq!(Some(3).filter(is_even), None);
assert_eq!(Some(4).filter(is_even), Some(4));

pub fn or(self, optb: Option<T>) -> Option<T>

Returns the option if it contains a value, otherwise returns optb.

Arguments passed to or are eagerly evaluated; if you are passing the result of a function call, it is recommended to use or_else, which is lazily evaluated.

Examples

let x = Some(2);
let y = None;
assert_eq!(x.or(y), Some(2));

let x = None;
let y = Some(100);
assert_eq!(x.or(y), Some(100));

let x = Some(2);
let y = Some(100);
assert_eq!(x.or(y), Some(2));

let x: Option<u32> = None;
let y = None;
assert_eq!(x.or(y), None);

pub fn or_else<F>(self, f: F) -> Option<T>

where F: FnOnce() -> Option<T>,

Returns the option if it contains a value, otherwise calls f and returns the result.

Examples

fn nobody() -> Option<&'static str> { None }
fn vikings() -> Option<&'static str> { Some("vikings") }

assert_eq!(Some("barbarians").or_else(vikings), Some("barbarians"));
assert_eq!(None.or_else(vikings), Some("vikings"));
assert_eq!(None.or_else(nobody), None);

pub fn xor(self, optb: Option<T>) -> Option<T>

Returns Some if exactly one of self, optb is Some, otherwise returns None.

Examples

let x = Some(2);
let y: Option<u32> = None;
assert_eq!(x.xor(y), Some(2));

let x: Option<u32> = None;
let y = Some(2);
assert_eq!(x.xor(y), Some(2));

let x = Some(2);
let y = Some(2);
assert_eq!(x.xor(y), None);

let x: Option<u32> = None;
let y: Option<u32> = None;
assert_eq!(x.xor(y), None);

pub fn insert(&mut self, value: T) -> &mut T

Inserts value into the option, then returns a mutable reference to it.

If the option already contains a value, the old value is dropped.

See also Option::get_or_insert, which doesn’t update the value if the option already contains Some.

Example

let mut opt = None;
let val = opt.insert(1);
assert_eq!(*val, 1);
assert_eq!(opt.unwrap(), 1);
let val = opt.insert(2);
assert_eq!(*val, 2);
*val = 3;
assert_eq!(opt.unwrap(), 3);

pub fn get_or_insert(&mut self, value: T) -> &mut T

Inserts value into the option if it is None, then returns a mutable reference to the contained value.

See also Option::insert, which updates the value even if the option already contains Some.

Examples

let mut x = None;

{
    let y: &mut u32 = x.get_or_insert(5);
    assert_eq!(y, &5);

    *y = 7;
}

assert_eq!(x, Some(7));

pub fn get_or_insert_default(&mut self) -> &mut T

where T: Default,

Inserts the default value into the option if it is None, then returns a mutable reference to the contained value.

Examples

let mut x = None;

{
    let y: &mut u32 = x.get_or_insert_default();
    assert_eq!(y, &0);

    *y = 7;
}

assert_eq!(x, Some(7));

pub fn get_or_insert_with<F>(&mut self, f: F) -> &mut T

where F: FnOnce() -> T,

Inserts a value computed from f into the option if it is None, then returns a mutable reference to the contained value.

Examples

let mut x = None;

{
    let y: &mut u32 = x.get_or_insert_with(|| 5);
    assert_eq!(y, &5);

    *y = 7;
}

assert_eq!(x, Some(7));

pub const fn take(&mut self) -> Option<T>

Takes the value out of the option, leaving a None in its place.

Examples

let mut x = Some(2);
let y = x.take();
assert_eq!(x, None);
assert_eq!(y, Some(2));

let mut x: Option<u32> = None;
let y = x.take();
assert_eq!(x, None);
assert_eq!(y, None);

pub fn take_if<P>(&mut self, predicate: P) -> Option<T>

where P: FnOnce(&mut T) -> bool,

Takes the value out of the option, but only if the predicate evaluates to true on a mutable reference to the value.

In other words, replaces self with None if the predicate returns true. This method operates similar to Option::take but conditional.

Examples

let mut x = Some(42);

let prev = x.take_if(|v| if *v == 42 {
    *v += 1;
    false
} else {
    false
});
assert_eq!(x, Some(43));
assert_eq!(prev, None);

let prev = x.take_if(|v| *v == 43);
assert_eq!(x, None);
assert_eq!(prev, Some(43));

pub const fn replace(&mut self, value: T) -> Option<T>

Replaces the actual value in the option by the value given in parameter, returning the old value if present, leaving a Some in its place without deinitializing either one.

Examples

let mut x = Some(2);
let old = x.replace(5);
assert_eq!(x, Some(5));
assert_eq!(old, Some(2));

let mut x = None;
let old = x.replace(3);
assert_eq!(x, Some(3));
assert_eq!(old, None);

pub fn zip<U>(self, other: Option<U>) -> Option<(T, U)>

Zips self with another Option.

If self is Some(s) and other is Some(o), this method returns Some((s, o)). Otherwise, None is returned.

Examples

let x = Some(1);
let y = Some("hi");
let z = None::<u8>;

assert_eq!(x.zip(y), Some((1, "hi")));
assert_eq!(x.zip(z), None);

pub fn zip_with<U, F, R>(self, other: Option<U>, f: F) -> Option<R>

where F: FnOnce(T, U) -> R,

🔬This is a nightly-only experimental API. (option_zip)

Zips self and another Option with function f.

If self is Some(s) and other is Some(o), this method returns Some(f(s, o)). Otherwise, None is returned.

Examples

#![feature(option_zip)]

#[derive(Debug, PartialEq)]
struct Point {
    x: f64,
    y: f64,
}

impl Point {
    fn new(x: f64, y: f64) -> Self {
        Self { x, y }
    }
}

let x = Some(17.5);
let y = Some(42.7);

assert_eq!(x.zip_with(y, Point::new), Some(Point { x: 17.5, y: 42.7 }));
assert_eq!(x.zip_with(None, Point::new), None);

impl<T, U> Option<(T, U)>

pub fn unzip(self) -> (Option<T>, Option<U>)

Unzips an option containing a tuple of two options.

If self is Some((a, b)) this method returns (Some(a), Some(b)). Otherwise, (None, None) is returned.

Examples

let x = Some((1, "hi"));
let y = None::<(u8, u32)>;

assert_eq!(x.unzip(), (Some(1), Some("hi")));
assert_eq!(y.unzip(), (None, None));

impl<T> Option<&T>

pub const fn copied(self) -> Option<T>

where T: Copy,

Maps an Option<&T> to an Option<T> by copying the contents of the option.

Examples

let x = 12;
let opt_x = Some(&x);
assert_eq!(opt_x, Some(&12));
let copied = opt_x.copied();
assert_eq!(copied, Some(12));

pub fn cloned(self) -> Option<T>

where T: Clone,

Maps an Option<&T> to an Option<T> by cloning the contents of the option.

Examples

let x = 12;
let opt_x = Some(&x);
assert_eq!(opt_x, Some(&12));
let cloned = opt_x.cloned();
assert_eq!(cloned, Some(12));

impl<T> Option<&mut T>

pub const fn copied(self) -> Option<T>

where T: Copy,

Maps an Option<&mut T> to an Option<T> by copying the contents of the option.

Examples

let mut x = 12;
let opt_x = Some(&mut x);
assert_eq!(opt_x, Some(&mut 12));
let copied = opt_x.copied();
assert_eq!(copied, Some(12));

pub fn cloned(self) -> Option<T>

where T: Clone,

Maps an Option<&mut T> to an Option<T> by cloning the contents of the option.

Examples

let mut x = 12;
let opt_x = Some(&mut x);
assert_eq!(opt_x, Some(&mut 12));
let cloned = opt_x.cloned();
assert_eq!(cloned, Some(12));

impl<T, E> Option<Result<T, E>>

pub const fn transpose(self) -> Result<Option<T>, E>

Transposes an Option of a Result into a Result of an Option.

None will be mapped to Ok(None). Some(Ok(_)) and Some(Err(_)) will be mapped to Ok(Some(_)) and Err(_).

Examples

#[derive(Debug, Eq, PartialEq)]
struct SomeErr;

let x: Result<Option<i32>, SomeErr> = Ok(Some(5));
let y: Option<Result<i32, SomeErr>> = Some(Ok(5));
assert_eq!(x, y.transpose());

impl<T> Option<Option<T>>

pub const fn flatten(self) -> Option<T>

Converts from Option<Option<T>> to Option<T>.

Examples

Basic usage:

let x: Option<Option<u32>> = Some(Some(6));
assert_eq!(Some(6), x.flatten());

let x: Option<Option<u32>> = Some(None);
assert_eq!(None, x.flatten());

let x: Option<Option<u32>> = None;
assert_eq!(None, x.flatten());

Flattening only removes one level of nesting at a time:

let x: Option<Option<Option<u32>>> = Some(Some(Some(6)));
assert_eq!(Some(Some(6)), x.flatten());
assert_eq!(Some(6), x.flatten().flatten());

Trait Implementations

impl<T> Archive for Option<T>

where T: Archive,

type Archived = ArchivedOption<<T as Archive>::Archived>

The archived representation of this type.

type Resolver = Option<<T as Archive>::Resolver>

The resolver for this type. It must contain all the additional information from serializing needed to make the archived type from the normal type.

fn resolve( &self, resolver: <Option<T> as Archive>::Resolver, out: Place<<Option<T> as Archive>::Archived>, )

Creates the archived version of this value at the given position and writes it to the given output.

const COPY_OPTIMIZATION: CopyOptimization<Self> = _

An optimization flag that allows the bytes of this type to be copied directly to a writer instead of calling serialize.

impl<T> ArchiveWith<Option<Box<T>>> for Niche

where T: ArchiveUnsized + ?Sized, <<T as ArchiveUnsized>::Archived as ArchivePointee>::ArchivedMetadata: Default,

type Archived = ArchivedOptionBox<<T as ArchiveUnsized>::Archived>

The archived type of Self with F.

type Resolver = OptionBoxResolver

The resolver of a Self with F.

fn resolve_with( field: &Option<Box<T>>, resolver: <Niche as ArchiveWith<Option<Box<T>>>>::Resolver, out: Place<<Niche as ArchiveWith<Option<Box<T>>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl ArchiveWith<Option<NonZero<i128>>> for Niche

type Archived = ArchivedOptionNonZeroI128

The archived type of Self with F.

type Resolver = ()

The resolver of a Self with F.

fn resolve_with( field: &Option<NonZero<i128>>, _: <Niche as ArchiveWith<Option<NonZero<i128>>>>::Resolver, out: Place<<Niche as ArchiveWith<Option<NonZero<i128>>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl ArchiveWith<Option<NonZero<i16>>> for Niche

type Archived = ArchivedOptionNonZeroI16

The archived type of Self with F.

type Resolver = ()

The resolver of a Self with F.

fn resolve_with( field: &Option<NonZero<i16>>, _: <Niche as ArchiveWith<Option<NonZero<i16>>>>::Resolver, out: Place<<Niche as ArchiveWith<Option<NonZero<i16>>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl ArchiveWith<Option<NonZero<i32>>> for Niche

type Archived = ArchivedOptionNonZeroI32

The archived type of Self with F.

type Resolver = ()

The resolver of a Self with F.

fn resolve_with( field: &Option<NonZero<i32>>, _: <Niche as ArchiveWith<Option<NonZero<i32>>>>::Resolver, out: Place<<Niche as ArchiveWith<Option<NonZero<i32>>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl ArchiveWith<Option<NonZero<i64>>> for Niche

type Archived = ArchivedOptionNonZeroI64

The archived type of Self with F.

type Resolver = ()

The resolver of a Self with F.

fn resolve_with( field: &Option<NonZero<i64>>, _: <Niche as ArchiveWith<Option<NonZero<i64>>>>::Resolver, out: Place<<Niche as ArchiveWith<Option<NonZero<i64>>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl ArchiveWith<Option<NonZero<i8>>> for Niche

type Archived = ArchivedOptionNonZeroI8

The archived type of Self with F.

type Resolver = ()

The resolver of a Self with F.

fn resolve_with( field: &Option<NonZero<i8>>, _: <Niche as ArchiveWith<Option<NonZero<i8>>>>::Resolver, out: Place<<Niche as ArchiveWith<Option<NonZero<i8>>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl ArchiveWith<Option<NonZero<isize>>> for Niche

type Archived = ArchivedOptionNonZeroI32

The archived type of Self with F.

type Resolver = ()

The resolver of a Self with F.

fn resolve_with( field: &Option<NonZero<isize>>, _: <Niche as ArchiveWith<Option<NonZero<isize>>>>::Resolver, out: Place<<Niche as ArchiveWith<Option<NonZero<isize>>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl ArchiveWith<Option<NonZero<u128>>> for Niche

type Archived = ArchivedOptionNonZeroU128

The archived type of Self with F.

type Resolver = ()

The resolver of a Self with F.

fn resolve_with( field: &Option<NonZero<u128>>, _: <Niche as ArchiveWith<Option<NonZero<u128>>>>::Resolver, out: Place<<Niche as ArchiveWith<Option<NonZero<u128>>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl ArchiveWith<Option<NonZero<u16>>> for Niche

type Archived = ArchivedOptionNonZeroU16

The archived type of Self with F.

type Resolver = ()

The resolver of a Self with F.

fn resolve_with( field: &Option<NonZero<u16>>, _: <Niche as ArchiveWith<Option<NonZero<u16>>>>::Resolver, out: Place<<Niche as ArchiveWith<Option<NonZero<u16>>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl ArchiveWith<Option<NonZero<u32>>> for Niche

type Archived = ArchivedOptionNonZeroU32

The archived type of Self with F.

type Resolver = ()

The resolver of a Self with F.

fn resolve_with( field: &Option<NonZero<u32>>, _: <Niche as ArchiveWith<Option<NonZero<u32>>>>::Resolver, out: Place<<Niche as ArchiveWith<Option<NonZero<u32>>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl ArchiveWith<Option<NonZero<u64>>> for Niche

type Archived = ArchivedOptionNonZeroU64

The archived type of Self with F.

type Resolver = ()

The resolver of a Self with F.

fn resolve_with( field: &Option<NonZero<u64>>, _: <Niche as ArchiveWith<Option<NonZero<u64>>>>::Resolver, out: Place<<Niche as ArchiveWith<Option<NonZero<u64>>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl ArchiveWith<Option<NonZero<u8>>> for Niche

type Archived = ArchivedOptionNonZeroU8

The archived type of Self with F.

type Resolver = ()

The resolver of a Self with F.

fn resolve_with( field: &Option<NonZero<u8>>, _: <Niche as ArchiveWith<Option<NonZero<u8>>>>::Resolver, out: Place<<Niche as ArchiveWith<Option<NonZero<u8>>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl ArchiveWith<Option<NonZero<usize>>> for Niche

type Archived = ArchivedOptionNonZeroU32

The archived type of Self with F.

type Resolver = ()

The resolver of a Self with F.

fn resolve_with( field: &Option<NonZero<usize>>, _: <Niche as ArchiveWith<Option<NonZero<usize>>>>::Resolver, out: Place<<Niche as ArchiveWith<Option<NonZero<usize>>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl<A, O> ArchiveWith<Option<O>> for Map<A>

where A: ArchiveWith<O>,

type Archived = ArchivedOption<<A as ArchiveWith<O>>::Archived>

The archived type of Self with F.

type Resolver = Option<<A as ArchiveWith<O>>::Resolver>

The resolver of a Self with F.

fn resolve_with( field: &Option<O>, resolver: <Map<A> as ArchiveWith<Option<O>>>::Resolver, out: Place<<Map<A> as ArchiveWith<Option<O>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl<T> ArchiveWith<Option<T>> for DefaultNiche

where T: Archive, DefaultNiche: Niching<<T as Archive>::Archived>,

type Archived = NichedOption<<T as Archive>::Archived, DefaultNiche>

The archived type of Self with F.

type Resolver = Option<<T as Archive>::Resolver>

The resolver of a Self with F.

fn resolve_with( field: &Option<T>, resolver: <DefaultNiche as ArchiveWith<Option<T>>>::Resolver, out: Place<<DefaultNiche as ArchiveWith<Option<T>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl<T, W, N> ArchiveWith<Option<T>> for MapNiche<W, N>

where W: ArchiveWith<T> + ?Sized, N: Niching<<W as ArchiveWith<T>>::Archived> + ?Sized,

type Archived = NichedOption<<W as ArchiveWith<T>>::Archived, N>

The archived type of Self with F.

type Resolver = Option<<W as ArchiveWith<T>>::Resolver>

The resolver of a Self with F.

fn resolve_with( field: &Option<T>, resolver: <MapNiche<W, N> as ArchiveWith<Option<T>>>::Resolver, out: Place<<MapNiche<W, N> as ArchiveWith<Option<T>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl<T, N> ArchiveWith<Option<T>> for NicheInto<N>

where T: Archive, N: Niching<<T as Archive>::Archived> + ?Sized,

type Archived = NichedOption<<T as Archive>::Archived, N>

The archived type of Self with F.

type Resolver = Option<<T as Archive>::Resolver>

The resolver of a Self with F.

fn resolve_with( field: &Option<T>, resolver: <NicheInto<N> as ArchiveWith<Option<T>>>::Resolver, out: Place<<NicheInto<N> as ArchiveWith<Option<T>>>::Archived>, )

Resolves the archived type using a reference to the field type F.

impl<T> AsPyPointer for Option<T>

where T: AsPyPointer,

Convert None into a null pointer.

fn as_ptr(&self) -> *mut PyObject

Returns the underlying FFI pointer as a borrowed pointer.

impl<T> Clone for Option<T>

where T: Clone,

fn clone(&self) -> Option<T>

Returns a copy of the value.

fn clone_from(&mut self, source: &Option<T>)

Performs copy-assignment from source.

impl<T: ConstDefault> ConstDefault for Option<T>

const DEFAULT: Self

Returns the compile-time “default value” for a type.

impl<T> Debug for Option<T>

where T: Debug,

fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>

Formats the value using the given formatter.

impl<T> Default for Option<T>

fn default() -> Option<T>

Returns None.

Examples

let opt: Option<u32> = Option::default();
assert!(opt.is_none());

impl<'de, T> Deserialize<'de> for Option<T>

where T: Deserialize<'de>,

fn deserialize<D>( deserializer: D, ) -> Result<Option<T>, <D as Deserializer<'de>>::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl<T, D> Deserialize<Option<T>, D> for ArchivedOption<<T as Archive>::Archived>

where T: Archive, <T as Archive>::Archived: Deserialize<T, D>, D: Fallible + ?Sized,

fn deserialize( &self, deserializer: &mut D, ) -> Result<Option<T>, <D as Fallible>::Error>

Deserializes using the given deserializer

impl<T, N, D> Deserialize<Option<T>, D> for NichedOption<<T as Archive>::Archived, N>

where T: Archive, <T as Archive>::Archived: Deserialize<T, D>, N: Niching<<T as Archive>::Archived> + ?Sized, D: Fallible + ?Sized,

fn deserialize( &self, deserializer: &mut D, ) -> Result<Option<T>, <D as Fallible>::Error>

Deserializes using the given deserializer

impl<A, O, D> DeserializeWith<ArchivedOption<<A as ArchiveWith<O>>::Archived>, Option<O>, D> for Map<A>

where D: Fallible + ?Sized, A: ArchiveWith<O> + DeserializeWith<<A as ArchiveWith<O>>::Archived, O, D>,

fn deserialize_with( field: &ArchivedOption<<A as ArchiveWith<O>>::Archived>, d: &mut D, ) -> Result<Option<O>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<T, D> DeserializeWith<ArchivedOptionBox<<T as ArchiveUnsized>::Archived>, Option<Box<T>>, D> for Niche

where T: ArchiveUnsized + LayoutRaw + Pointee + ?Sized, <T as ArchiveUnsized>::Archived: DeserializeUnsized<T, D>, D: Fallible + ?Sized, <D as Fallible>::Error: Source,

fn deserialize_with( field: &ArchivedOptionBox<<T as ArchiveUnsized>::Archived>, deserializer: &mut D, ) -> Result<Option<Box<T>>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<D> DeserializeWith<ArchivedOptionNonZeroI128, Option<NonZero<i128>>, D> for Niche

where D: Fallible + ?Sized,

fn deserialize_with( field: &ArchivedOptionNonZeroI128, _: &mut D, ) -> Result<Option<NonZero<i128>>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<D> DeserializeWith<ArchivedOptionNonZeroI16, Option<NonZero<i16>>, D> for Niche

where D: Fallible + ?Sized,

fn deserialize_with( field: &ArchivedOptionNonZeroI16, _: &mut D, ) -> Result<Option<NonZero<i16>>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<D> DeserializeWith<ArchivedOptionNonZeroI32, Option<NonZero<i32>>, D> for Niche

where D: Fallible + ?Sized,

fn deserialize_with( field: &ArchivedOptionNonZeroI32, _: &mut D, ) -> Result<Option<NonZero<i32>>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<D> DeserializeWith<ArchivedOptionNonZeroI32, Option<NonZero<isize>>, D> for Niche

where D: Fallible + ?Sized,

fn deserialize_with( field: &ArchivedOptionNonZeroI32, _: &mut D, ) -> Result<Option<NonZero<isize>>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<D> DeserializeWith<ArchivedOptionNonZeroI64, Option<NonZero<i64>>, D> for Niche

where D: Fallible + ?Sized,

fn deserialize_with( field: &ArchivedOptionNonZeroI64, _: &mut D, ) -> Result<Option<NonZero<i64>>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<D> DeserializeWith<ArchivedOptionNonZeroI8, Option<NonZero<i8>>, D> for Niche

where D: Fallible + ?Sized,

fn deserialize_with( field: &ArchivedOptionNonZeroI8, _: &mut D, ) -> Result<Option<NonZero<i8>>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<D> DeserializeWith<ArchivedOptionNonZeroU128, Option<NonZero<u128>>, D> for Niche

where D: Fallible + ?Sized,

fn deserialize_with( field: &ArchivedOptionNonZeroU128, _: &mut D, ) -> Result<Option<NonZero<u128>>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<D> DeserializeWith<ArchivedOptionNonZeroU16, Option<NonZero<u16>>, D> for Niche

where D: Fallible + ?Sized,

fn deserialize_with( field: &ArchivedOptionNonZeroU16, _: &mut D, ) -> Result<Option<NonZero<u16>>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<D> DeserializeWith<ArchivedOptionNonZeroU32, Option<NonZero<u32>>, D> for Niche

where D: Fallible + ?Sized,

fn deserialize_with( field: &ArchivedOptionNonZeroU32, _: &mut D, ) -> Result<Option<NonZero<u32>>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<D> DeserializeWith<ArchivedOptionNonZeroU32, Option<NonZero<usize>>, D> for Niche

where D: Fallible + ?Sized,

fn deserialize_with( field: &ArchivedOptionNonZeroU32, _: &mut D, ) -> Result<Option<NonZero<usize>>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<D> DeserializeWith<ArchivedOptionNonZeroU64, Option<NonZero<u64>>, D> for Niche

where D: Fallible + ?Sized,

fn deserialize_with( field: &ArchivedOptionNonZeroU64, _: &mut D, ) -> Result<Option<NonZero<u64>>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<D> DeserializeWith<ArchivedOptionNonZeroU8, Option<NonZero<u8>>, D> for Niche

where D: Fallible + ?Sized,

fn deserialize_with( field: &ArchivedOptionNonZeroU8, _: &mut D, ) -> Result<Option<NonZero<u8>>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<T, D> DeserializeWith<NichedOption<<T as Archive>::Archived, DefaultNiche>, Option<T>, D> for DefaultNiche

where T: Archive, <T as Archive>::Archived: Deserialize<T, D>, DefaultNiche: Niching<<T as Archive>::Archived>, D: Fallible + ?Sized,

fn deserialize_with( field: &NichedOption<<T as Archive>::Archived, DefaultNiche>, deserializer: &mut D, ) -> Result<Option<T>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<T, N, D> DeserializeWith<NichedOption<<T as Archive>::Archived, N>, Option<T>, D> for NicheInto<N>

where T: Archive, <T as Archive>::Archived: Deserialize<T, D>, N: Niching<<T as Archive>::Archived> + ?Sized, D: Fallible + ?Sized,

fn deserialize_with( field: &NichedOption<<T as Archive>::Archived, N>, deserializer: &mut D, ) -> Result<Option<T>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<T, W, N, D> DeserializeWith<NichedOption<<W as ArchiveWith<T>>::Archived, N>, Option<T>, D> for MapNiche<W, N>

where W: ArchiveWith<T> + DeserializeWith<<W as ArchiveWith<T>>::Archived, T, D>, N: Niching<<W as ArchiveWith<T>>::Archived> + ?Sized, D: Fallible + ?Sized,

fn deserialize_with( field: &NichedOption<<W as ArchiveWith<T>>::Archived, N>, deserializer: &mut D, ) -> Result<Option<T>, <D as Fallible>::Error>

Deserializes the field type F using the given deserializer.

impl<T> ExtOption<T> for Option<T>

fn contains<U: PartialEq<T>>(&self, x: &U) -> bool

Returns true if the option is a Some value containing the given value.

fn reduce<F: FnOnce(T, T) -> T>(self, other: Option<T>, f: F) -> Option<T>

Merges self with another Option.

fn fmt_or_empty(&self) -> OptionFmt<'_, T>

Format some value, or display an empty string if it’s None.

fn fmt_or<U: Display>(&self, u: U) -> OptionFmtOr<'_, T, U>

Format some value, or an alternative if it’s None.

fn fmt_or_else<U: Display, F: Fn() -> U>( &self, f: F, ) -> OptionFmtOrElse<'_, T, F>

Format some value, or run an alternative closure if it’s None.

impl<'a> From<&'a Current> for Option<&'a Id>

fn from(cur: &'a Current) -> Option<&'a Id>

Converts to this type from the input type.

impl<'a> From<&'a Current> for Option<&'static Metadata<'static>>

fn from(cur: &'a Current) -> Option<&'static Metadata<'static>>

Converts to this type from the input type.

impl<'a> From<&'a Current> for Option<Id>

fn from(cur: &'a Current) -> Option<Id>

Converts to this type from the input type.

impl<'a> From<&'a EnteredSpan> for Option<&'a Id>

fn from(span: &'a EnteredSpan) -> Option<&'a Id>

Converts to this type from the input type.

impl<'a> From<&'a EnteredSpan> for Option<Id>

fn from(span: &'a EnteredSpan) -> Option<Id>

Converts to this type from the input type.

impl<'a> From<&'a Id> for Option<Id>

fn from(id: &'a Id) -> Option<Id>

Converts to this type from the input type.

impl<'a, T> From<&'a Option<T>> for Option<&'a T>

fn from(o: &'a Option<T>) -> Option<&'a T>

Converts from &Option<T> to Option<&T>.

Examples

Converts an Option<String> into an Option<usize>, preserving the original. The map method takes the self argument by value, consuming the original, so this technique uses from to first take an Option to a reference to the value inside the original.

let s: Option<String> = Some(String::from("Hello, Rustaceans!"));
let o: Option<usize> = Option::from(&s).map(|ss: &String| ss.len());

println!("Can still print s: {s:?}");

assert_eq!(o, Some(18));

impl<'a> From<&'a Span> for Option<&'a Id>

fn from(span: &'a Span) -> Option<&'a Id>

Converts to this type from the input type.

impl<'a> From<&'a Span> for Option<Id>

fn from(span: &'a Span) -> Option<Id>

Converts to this type from the input type.

impl<'a, T> From<&'a mut Option<T>> for Option<&'a mut T>

fn from(o: &'a mut Option<T>) -> Option<&'a mut T>

Converts from &mut Option<T> to Option<&mut T>

Examples

let mut s = Some(String::from("Hello"));
let o: Option<&mut String> = Option::from(&mut s);

match o {
    Some(t) => *t = String::from("Hello, Rustaceans!"),
    None => (),
}

assert_eq!(s, Some(String::from("Hello, Rustaceans!")));

impl From<Current> for Option<Id>

fn from(cur: Current) -> Option<Id>

Converts to this type from the input type.

impl From<LevelFilter> for Option<Level>

fn from(filter: LevelFilter) -> Option<Level>

Converts to this type from the input type.

impl From<Option<Level>> for LevelFilter

fn from(level: Option<Level>) -> LevelFilter

Converts to this type from the input type.

impl<T> From<Option<T>> for JsValue

where JsValue: From<T>,

fn from(s: Option<T>) -> JsValue

Converts to this type from the input type.

impl From<Span> for Option<Id>

fn from(span: Span) -> Option<Id>

Converts to this type from the input type.

impl<T> From<T> for Option<T>

fn from(val: T) -> Option<T>

Moves val into a new Some.

Examples

let o: Option<u8> = Option::from(67);

assert_eq!(Some(67), o);

impl<A, V> FromIterator<Option<A>> for Option<V>

where V: FromIterator<A>,

fn from_iter<I>(iter: I) -> Option<V>

where I: IntoIterator<Item = Option<A>>,

Takes each element in the Iterator: if it is None, no further elements are taken, and the None is returned. Should no None occur, a container of type V containing the values of each Option is returned.

Examples

Here is an example which increments every integer in a vector. We use the checked variant of add that returns None when the calculation would result in an overflow.

let items = vec![0_u16, 1, 2];

let res: Option<Vec<u16>> = items
    .iter()
    .map(|x| x.checked_add(1))
    .collect();

assert_eq!(res, Some(vec![1, 2, 3]));

As you can see, this will return the expected, valid items.

Here is another example that tries to subtract one from another list of integers, this time checking for underflow:

let items = vec![2_u16, 1, 0];

let res: Option<Vec<u16>> = items
    .iter()
    .map(|x| x.checked_sub(1))
    .collect();

assert_eq!(res, None);

Since the last element is zero, it would underflow. Thus, the resulting value is None.

Here is a variation on the previous example, showing that no further elements are taken from iter after the first None.

let items = vec![3_u16, 2, 1, 10];

let mut shared = 0;

let res: Option<Vec<u16>> = items
    .iter()
    .map(|x| { shared += x; x.checked_sub(2) })
    .collect();

assert_eq!(res, None);
assert_eq!(shared, 6);

Since the third element caused an underflow, no further elements were taken, so the final value of shared is 6 (= 3 + 2 + 1), not 16.

impl<T, V> FromIteratorIn<Option<T>> for Option<V>

where V: FromIteratorIn<T>,

type Alloc = <V as FromIteratorIn<T>>::Alloc

The allocator type

fn from_iter_in<I>( iter: I, alloc: <Option<V> as FromIteratorIn<Option<T>>>::Alloc, ) -> Option<V>

where I: IntoIterator<Item = Option<T>>,

Similar to FromIterator::from_iter, but with a given allocator.

impl<C, T> FromParallelIterator<Option<T>> for Option<C>

where C: FromParallelIterator<T>, T: Send,

Collect an arbitrary Option-wrapped collection.

If any item is None, then all previous items collected are discarded, and it returns only None.

fn from_par_iter<I>(par_iter: I) -> Option<C>

where I: IntoParallelIterator<Item = Option<T>>,

Creates an instance of the collection from the parallel iterator par_iter.

impl<'py, T> FromPyObject<'py> for Option<T>

where T: FromPyObject<'py>,

fn extract_bound(obj: &Bound<'py, PyAny>) -> Result<Option<T>, PyErr>

Extracts Self from the bound smart pointer obj.

impl<T> FromResidual<Option<Infallible>> for Option<T>

fn from_residual(residual: Option<Infallible>) -> Option<T>

🔬This is a nightly-only experimental API. (try_trait_v2)

Constructs the type from a compatible Residual type.

impl<T> FromResidual<Yeet<()>> for Option<T>

fn from_residual(_: Yeet<()>) -> Option<T>

🔬This is a nightly-only experimental API. (try_trait_v2)

Constructs the type from a compatible Residual type.

impl<T> FromWasmAbi for Option<*const T>

type Abi = f64

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: f64) -> Option<*const T>

Recover a Self from Self::Abi.

impl<T> FromWasmAbi for Option<*mut T>

type Abi = f64

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: f64) -> Option<*mut T>

Recover a Self from Self::Abi.

impl<T> FromWasmAbi for Option<T>

where T: OptionFromWasmAbi,

type Abi = <T as FromWasmAbi>::Abi

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: <T as FromWasmAbi>::Abi) -> Option<T>

Recover a Self from Self::Abi.

impl FromWasmAbi for Option<f32>

type Abi = f64

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: <Option<f32> as FromWasmAbi>::Abi) -> Option<f32>

Recover a Self from Self::Abi.

impl FromWasmAbi for Option<f64>

type Abi = Option<f64>

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: <Option<f64> as FromWasmAbi>::Abi) -> Option<f64>

Recover a Self from Self::Abi.

impl FromWasmAbi for Option<i128>

type Abi = Option<i128>

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: <Option<i128> as FromWasmAbi>::Abi) -> Option<i128>

Recover a Self from Self::Abi.

impl FromWasmAbi for Option<i32>

type Abi = f64

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: <Option<i32> as FromWasmAbi>::Abi) -> Option<i32>

Recover a Self from Self::Abi.

impl FromWasmAbi for Option<i64>

type Abi = Option<i64>

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: <Option<i64> as FromWasmAbi>::Abi) -> Option<i64>

Recover a Self from Self::Abi.

impl FromWasmAbi for Option<isize>

type Abi = f64

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: <Option<isize> as FromWasmAbi>::Abi) -> Option<isize>

Recover a Self from Self::Abi.

impl FromWasmAbi for Option<u128>

type Abi = Option<u128>

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: <Option<u128> as FromWasmAbi>::Abi) -> Option<u128>

Recover a Self from Self::Abi.

impl FromWasmAbi for Option<u32>

type Abi = f64

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: <Option<u32> as FromWasmAbi>::Abi) -> Option<u32>

Recover a Self from Self::Abi.

impl FromWasmAbi for Option<u64>

type Abi = Option<u64>

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: <Option<u64> as FromWasmAbi>::Abi) -> Option<u64>

Recover a Self from Self::Abi.

impl FromWasmAbi for Option<usize>

type Abi = f64

The Wasm ABI type that this converts from when coming back out from the ABI boundary.

unsafe fn from_abi(js: <Option<usize> as FromWasmAbi>::Abi) -> Option<usize>

Recover a Self from Self::Abi.

impl<T> Hash for Option<T>

where T: Hash,

fn hash<__H>(&self, state: &mut __H)

where __H: Hasher,

Feeds this value into the given Hasher.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl<'a, T> IntoIterator for &'a Option<T>

type Item = &'a T

The type of the elements being iterated over.

type IntoIter = Iter<'a, T>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Iter<'a, T>

Creates an iterator from a value.

impl<'a, T> IntoIterator for &'a mut Option<T>

type Item = &'a mut T

The type of the elements being iterated over.

type IntoIter = IterMut<'a, T>

Which kind of iterator are we turning this into?

fn into_iter(self) -> IterMut<'a, T>

Creates an iterator from a value.

impl<T> IntoIterator for Option<T>

fn into_iter(self) -> IntoIter<T>

Returns a consuming iterator over the possibly contained value.

Examples

let x = Some("string");
let v: Vec<&str> = x.into_iter().collect();
assert_eq!(v, ["string"]);

let x = None;
let v: Vec<&str> = x.into_iter().collect();
assert!(v.is_empty());

type Item = T

The type of the elements being iterated over.

type IntoIter = IntoIter<T>

Which kind of iterator are we turning this into?

impl IntoOptionalRegion for Option<Region>

fn into_optional_region(self) -> Option<Region>

Converts the type into an Option<Region>.

impl<'a, T> IntoParallelIterator for &'a Option<T>

where T: Sync,

type Item = &'a T

The type of item that the parallel iterator will produce.

type Iter = Iter<'a, T>

The parallel iterator type that will be created.

fn into_par_iter(self) -> <&'a Option<T> as IntoParallelIterator>::Iter

Converts self into a parallel iterator.

impl<'a, T> IntoParallelIterator for &'a mut Option<T>

where T: Send,

type Item = &'a mut T

The type of item that the parallel iterator will produce.

type Iter = IterMut<'a, T>

The parallel iterator type that will be created.

fn into_par_iter(self) -> <&'a mut Option<T> as IntoParallelIterator>::Iter

Converts self into a parallel iterator.

impl<T> IntoParallelIterator for Option<T>

where T: Send,

type Item = T

The type of item that the parallel iterator will produce.

type Iter = IntoIter<T>

The parallel iterator type that will be created.

fn into_par_iter(self) -> <Option<T> as IntoParallelIterator>::Iter

Converts self into a parallel iterator.

impl<T> IntoPy<Py<PyAny>> for Option<T>

where T: IntoPy<Py<PyAny>>,

fn into_py(self, py: Python<'_>) -> Py<PyAny>

👎Deprecated since 0.23.0: IntoPy is going to be replaced by IntoPyObject. See the migration guide (https://pyo3.rs/v0.23.0/migration) for more information.

Performs the conversion.

impl<'a, 'py, T> IntoPyObject<'py> for &'a Option<T>

where &'a T: IntoPyObject<'py>,

type Target = PyAny

The Python output type

type Output = Bound<'py, <&'a Option<T> as IntoPyObject<'py>>::Target>

The smart pointer type to use.

type Error = <&'a T as IntoPyObject<'py>>::Error

The type returned in the event of a conversion error.

fn into_pyobject( self, py: Python<'py>, ) -> Result<<&'a Option<T> as IntoPyObject<'py>>::Output, <&'a Option<T> as IntoPyObject<'py>>::Error>

Performs the conversion.

impl<'py, T> IntoPyObject<'py> for Option<T>

where T: IntoPyObject<'py>,

type Target = PyAny

The Python output type

type Output = Bound<'py, <Option<T> as IntoPyObject<'py>>::Target>

The smart pointer type to use.

type Error = <T as IntoPyObject<'py>>::Error

The type returned in the event of a conversion error.

fn into_pyobject( self, py: Python<'py>, ) -> Result<<Option<T> as IntoPyObject<'py>>::Output, <Option<T> as IntoPyObject<'py>>::Error>

Performs the conversion.

impl<T> IntoWasmAbi for Option<*const T>

type Abi = f64

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> f64

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl<T> IntoWasmAbi for Option<*mut T>

type Abi = f64

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> f64

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl<T> IntoWasmAbi for Option<T>

where T: OptionIntoWasmAbi,

type Abi = <T as IntoWasmAbi>::Abi

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> <T as IntoWasmAbi>::Abi

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl IntoWasmAbi for Option<f32>

type Abi = f64

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> <Option<f32> as IntoWasmAbi>::Abi

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl IntoWasmAbi for Option<f64>

type Abi = Option<f64>

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> <Option<f64> as IntoWasmAbi>::Abi

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl IntoWasmAbi for Option<i128>

type Abi = Option<i128>

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> <Option<i128> as IntoWasmAbi>::Abi

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl IntoWasmAbi for Option<i32>

type Abi = f64

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> <Option<i32> as IntoWasmAbi>::Abi

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl IntoWasmAbi for Option<i64>

type Abi = Option<i64>

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> <Option<i64> as IntoWasmAbi>::Abi

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl IntoWasmAbi for Option<isize>

type Abi = f64

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> <Option<isize> as IntoWasmAbi>::Abi

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl IntoWasmAbi for Option<u128>

type Abi = Option<u128>

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> <Option<u128> as IntoWasmAbi>::Abi

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl IntoWasmAbi for Option<u32>

type Abi = f64

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> <Option<u32> as IntoWasmAbi>::Abi

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl IntoWasmAbi for Option<u64>

type Abi = Option<u64>

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> <Option<u64> as IntoWasmAbi>::Abi

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl IntoWasmAbi for Option<usize>

type Abi = f64

The Wasm ABI type that this converts into when crossing the ABI boundary.

fn into_abi(self) -> <Option<usize> as IntoWasmAbi>::Abi

Convert self into Self::Abi so that it can be sent across the wasm ABI boundary.

impl MemPod for Option<NonZeroI128>

Available on crate feature unsafe_layout only.

fn zeroed() -> Self

Returns a new instance contrcuted from zeroes.

fn from_bytes(bytes: &[u8]) -> Self

Returns a new instance constructed from the given bytes.

fn as_bytes(&self) -> &[u8]

Returns the instance’s data as a slice of bytes.

fn as_bytes_mut(&mut self) -> &mut [u8]

Returns the instance’s data as a mutable slice of bytes.

impl MemPod for Option<NonZeroI16>

Available on crate feature unsafe_layout only.

fn zeroed() -> Self

Returns a new instance contrcuted from zeroes.

fn from_bytes(bytes: &[u8]) -> Self

Returns a new instance constructed from the given bytes.

fn as_bytes(&self) -> &[u8]

Returns the instance’s data as a slice of bytes.

fn as_bytes_mut(&mut self) -> &mut [u8]

Returns the instance’s data as a mutable slice of bytes.

impl MemPod for Option<NonZeroI32>

Available on crate feature unsafe_layout only.

fn zeroed() -> Self

Returns a new instance contrcuted from zeroes.

fn from_bytes(bytes: &[u8]) -> Self

Returns a new instance constructed from the given bytes.

fn as_bytes(&self) -> &[u8]

Returns the instance’s data as a slice of bytes.

fn as_bytes_mut(&mut self) -> &mut [u8]

Returns the instance’s data as a mutable slice of bytes.

impl MemPod for Option<NonZeroI64>

Available on crate feature unsafe_layout only.

fn zeroed() -> Self

Returns a new instance contrcuted from zeroes.

fn from_bytes(bytes: &[u8]) -> Self

Returns a new instance constructed from the given bytes.

fn as_bytes(&self) -> &[u8]

Returns the instance’s data as a slice of bytes.

fn as_bytes_mut(&mut self) -> &mut [u8]

Returns the instance’s data as a mutable slice of bytes.

impl MemPod for Option<NonZeroI8>

Available on crate feature unsafe_layout only.

fn zeroed() -> Self

Returns a new instance contrcuted from zeroes.

fn from_bytes(bytes: &[u8]) -> Self

Returns a new instance constructed from the given bytes.

fn as_bytes(&self) -> &[u8]

Returns the instance’s data as a slice of bytes.

fn as_bytes_mut(&mut self) -> &mut [u8]

Returns the instance’s data as a mutable slice of bytes.

impl MemPod for Option<NonZeroIsize>

Available on crate feature unsafe_layout only.

fn zeroed() -> Self

Returns a new instance contrcuted from zeroes.

fn from_bytes(bytes: &[u8]) -> Self

Returns a new instance constructed from the given bytes.

fn as_bytes(&self) -> &[u8]

Returns the instance’s data as a slice of bytes.

fn as_bytes_mut(&mut self) -> &mut [u8]

Returns the instance’s data as a mutable slice of bytes.

impl MemPod for Option<NonZeroU128>

Available on crate feature unsafe_layout only.

fn zeroed() -> Self

Returns a new instance contrcuted from zeroes.

fn from_bytes(bytes: &[u8]) -> Self

Returns a new instance constructed from the given bytes.

fn as_bytes(&self) -> &[u8]

Returns the instance’s data as a slice of bytes.

fn as_bytes_mut(&mut self) -> &mut [u8]

Returns the instance’s data as a mutable slice of bytes.

impl MemPod for Option<NonZeroU16>

Available on crate feature unsafe_layout only.

fn zeroed() -> Self

Returns a new instance contrcuted from zeroes.

fn from_bytes(bytes: &[u8]) -> Self

Returns a new instance constructed from the given bytes.

fn as_bytes(&self) -> &[u8]

Returns the instance’s data as a slice of bytes.

fn as_bytes_mut(&mut self) -> &mut [u8]

Returns the instance’s data as a mutable slice of bytes.

impl MemPod for Option<NonZeroU32>

Available on crate feature unsafe_layout only.

fn zeroed() -> Self

Returns a new instance contrcuted from zeroes.

fn from_bytes(bytes: &[u8]) -> Self

Returns a new instance constructed from the given bytes.

fn as_bytes(&self) -> &[u8]

Returns the instance’s data as a slice of bytes.

fn as_bytes_mut(&mut self) -> &mut [u8]

Returns the instance’s data as a mutable slice of bytes.

impl MemPod for Option<NonZeroU64>

Available on crate feature unsafe_layout only.

fn zeroed() -> Self

Returns a new instance contrcuted from zeroes.

fn from_bytes(bytes: &[u8]) -> Self

Returns a new instance constructed from the given bytes.

fn as_bytes(&self) -> &[u8]

Returns the instance’s data as a slice of bytes.

fn as_bytes_mut(&mut self) -> &mut [u8]

Returns the instance’s data as a mutable slice of bytes.

impl MemPod for Option<NonZeroU8>

Available on crate feature unsafe_layout only.

fn zeroed() -> Self

Returns a new instance contrcuted from zeroes.

fn from_bytes(bytes: &[u8]) -> Self

Returns a new instance constructed from the given bytes.

fn as_bytes(&self) -> &[u8]

Returns the instance’s data as a slice of bytes.

fn as_bytes_mut(&mut self) -> &mut [u8]

Returns the instance’s data as a mutable slice of bytes.

impl MemPod for Option<NonZeroUsize>

Available on crate feature unsafe_layout only.

fn zeroed() -> Self

Returns a new instance contrcuted from zeroes.

fn from_bytes(bytes: &[u8]) -> Self

Returns a new instance constructed from the given bytes.

fn as_bytes(&self) -> &[u8]

Returns the instance’s data as a slice of bytes.

fn as_bytes_mut(&mut self) -> &mut [u8]

Returns the instance’s data as a mutable slice of bytes.

impl<T: MemPod> MemPod for Option<T>

Available on crate feature unsafe_layout only.

fn zeroed() -> Self

Returns a new instance contrcuted from zeroes.

fn from_bytes(bytes: &[u8]) -> Self

Returns a new instance constructed from the given bytes.

fn as_bytes(&self) -> &[u8]

Returns the instance’s data as a slice of bytes.

fn as_bytes_mut(&mut self) -> &mut [u8]

Returns the instance’s data as a mutable slice of bytes.

impl<T> OptionExt<T> for Option<T>

fn into_error<E>(self) -> Result<T, E>

where E: Source,

Returns a Result with an error indicating that Some was expected but None was found.

fn into_trace<E, R>(self, trace: R) -> Result<T, E>

where E: Source, R: Debug + Display + Send + Sync + 'static,

Returns a Result with an error indicating that Some was expected but None was found, and with an additional trace message added.

fn into_with_trace<E, R, F>(self, f: F) -> Result<T, E>

where E: Source, R: Debug + Display + Send + Sync + 'static, F: FnOnce() -> R,

Returns a Result with an error indicating that Some was expected but None was found, and with an additional trace message added by evaluating the given function f. The function is evaluated only if an error occurred.

impl<T> Ord for Option<T>

where T: Ord,

fn cmp(&self, other: &Option<T>) -> Ordering

This method returns an Ordering between self and other.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

impl<T, U> PartialEq<Option<Box<T>>> for ArchivedOptionBox<U>

where U: ArchivePointee + PartialEq<T> + ?Sized, T: ?Sized,

fn eq(&self, other: &Option<Box<T>>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, N, Rhs> PartialEq<Option<Rhs>> for NichedOption<T, N>

where T: PartialEq<Rhs>, N: Niching<T> + ?Sized,

fn eq(&self, other: &Option<Rhs>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, U> PartialEq<Option<T>> for ArchivedOption<U>

where U: PartialEq<T>,

fn eq(&self, other: &Option<T>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T> PartialEq for Option<T>

where T: PartialEq,

fn eq(&self, other: &Option<T>) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl<T, U> PartialOrd<Option<T>> for ArchivedOption<U>

where U: PartialOrd<T>,

fn partial_cmp(&self, other: &Option<T>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T> PartialOrd for Option<T>

where T: PartialOrd,

fn partial_cmp(&self, other: &Option<T>) -> Option<Ordering>

This method returns an ordering between self and other values if one exists.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl<T, U> Product<Option<U>> for Option<T>

where T: Product<U>,

fn product<I>(iter: I) -> Option<T>

where I: Iterator<Item = Option<U>>,

Takes each element in the Iterator: if it is a None, no further elements are taken, and the None is returned. Should no None occur, the product of all elements is returned.

Examples

This multiplies each number in a vector of strings, if a string could not be parsed the operation returns None:

let nums = vec!["5", "10", "1", "2"];
let total: Option<usize> = nums.iter().map(|w| w.parse::<usize>().ok()).product();
assert_eq!(total, Some(100));
let nums = vec!["5", "10", "one", "2"];
let total: Option<usize> = nums.iter().map(|w| w.parse::<usize>().ok()).product();
assert_eq!(total, None);

impl<T> Residual<T> for Option<Infallible>

type TryType = Option<T>

🔬This is a nightly-only experimental API. (try_trait_v2_residual)

The “return” type of this meta-function.

impl<T, S> Serialize<S> for Option<T>

where T: Serialize<S>, S: Fallible + ?Sized,

fn serialize( &self, serializer: &mut S, ) -> Result<<Option<T> as Archive>::Resolver, <S as Fallible>::Error>

Writes the dependencies for the object and returns a resolver that can create the archived type.

impl<T> Serialize for Option<T>

where T: Serialize,

fn serialize<S>( &self, serializer: S, ) -> Result<<S as Serializer>::Ok, <S as Serializer>::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl<T, S> SerializeWith<Option<Box<T>>, S> for Niche

where T: SerializeUnsized<S> + ?Sized, S: Fallible + Writer + ?Sized, <<T as ArchiveUnsized>::Archived as ArchivePointee>::ArchivedMetadata: Default,

fn serialize_with( field: &Option<Box<T>>, serializer: &mut S, ) -> Result<<Niche as ArchiveWith<Option<Box<T>>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<S> SerializeWith<Option<NonZero<i128>>, S> for Niche

where S: Fallible + ?Sized,

fn serialize_with( _: &Option<NonZero<i128>>, _: &mut S, ) -> Result<<Niche as ArchiveWith<Option<NonZero<i128>>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<S> SerializeWith<Option<NonZero<i16>>, S> for Niche

where S: Fallible + ?Sized,

fn serialize_with( _: &Option<NonZero<i16>>, _: &mut S, ) -> Result<<Niche as ArchiveWith<Option<NonZero<i16>>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<S> SerializeWith<Option<NonZero<i32>>, S> for Niche

where S: Fallible + ?Sized,

fn serialize_with( _: &Option<NonZero<i32>>, _: &mut S, ) -> Result<<Niche as ArchiveWith<Option<NonZero<i32>>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<S> SerializeWith<Option<NonZero<i64>>, S> for Niche

where S: Fallible + ?Sized,

fn serialize_with( _: &Option<NonZero<i64>>, _: &mut S, ) -> Result<<Niche as ArchiveWith<Option<NonZero<i64>>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<S> SerializeWith<Option<NonZero<i8>>, S> for Niche

where S: Fallible + ?Sized,

fn serialize_with( _: &Option<NonZero<i8>>, _: &mut S, ) -> Result<<Niche as ArchiveWith<Option<NonZero<i8>>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<S> SerializeWith<Option<NonZero<isize>>, S> for Niche

where S: Fallible + ?Sized,

fn serialize_with( _: &Option<NonZero<isize>>, _: &mut S, ) -> Result<<Niche as ArchiveWith<Option<NonZero<isize>>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<S> SerializeWith<Option<NonZero<u128>>, S> for Niche

where S: Fallible + ?Sized,

fn serialize_with( _: &Option<NonZero<u128>>, _: &mut S, ) -> Result<<Niche as ArchiveWith<Option<NonZero<u128>>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<S> SerializeWith<Option<NonZero<u16>>, S> for Niche

where S: Fallible + ?Sized,

fn serialize_with( _: &Option<NonZero<u16>>, _: &mut S, ) -> Result<<Niche as ArchiveWith<Option<NonZero<u16>>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<S> SerializeWith<Option<NonZero<u32>>, S> for Niche

where S: Fallible + ?Sized,

fn serialize_with( _: &Option<NonZero<u32>>, _: &mut S, ) -> Result<<Niche as ArchiveWith<Option<NonZero<u32>>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<S> SerializeWith<Option<NonZero<u64>>, S> for Niche

where S: Fallible + ?Sized,

fn serialize_with( _: &Option<NonZero<u64>>, _: &mut S, ) -> Result<<Niche as ArchiveWith<Option<NonZero<u64>>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<S> SerializeWith<Option<NonZero<u8>>, S> for Niche

where S: Fallible + ?Sized,

fn serialize_with( _: &Option<NonZero<u8>>, _: &mut S, ) -> Result<<Niche as ArchiveWith<Option<NonZero<u8>>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<S> SerializeWith<Option<NonZero<usize>>, S> for Niche

where S: Fallible + ?Sized,

fn serialize_with( _: &Option<NonZero<usize>>, _: &mut S, ) -> Result<<Niche as ArchiveWith<Option<NonZero<usize>>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<A, O, S> SerializeWith<Option<O>, S> for Map<A>

where S: Fallible + ?Sized, A: ArchiveWith<O> + SerializeWith<O, S>,

fn serialize_with( field: &Option<O>, s: &mut S, ) -> Result<<Map<A> as ArchiveWith<Option<O>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<T, S> SerializeWith<Option<T>, S> for DefaultNiche

where T: Serialize<S>, DefaultNiche: Niching<<T as Archive>::Archived>, S: Fallible + ?Sized,

fn serialize_with( field: &Option<T>, serializer: &mut S, ) -> Result<<DefaultNiche as ArchiveWith<Option<T>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<T, W, N, S> SerializeWith<Option<T>, S> for MapNiche<W, N>

where W: SerializeWith<T, S> + ?Sized, N: Niching<<W as ArchiveWith<T>>::Archived> + ?Sized, S: Fallible + ?Sized,

fn serialize_with( field: &Option<T>, serializer: &mut S, ) -> Result<<MapNiche<W, N> as ArchiveWith<Option<T>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<T, N, S> SerializeWith<Option<T>, S> for NicheInto<N>

where T: Serialize<S>, N: Niching<<T as Archive>::Archived> + ?Sized, S: Fallible + ?Sized,

fn serialize_with( field: &Option<T>, serializer: &mut S, ) -> Result<<NicheInto<N> as ArchiveWith<Option<T>>>::Resolver, <S as Fallible>::Error>

Serializes the field type F using the given serializer.

impl<T, U> Sum<Option<U>> for Option<T>

where T: Sum<U>,

fn sum<I>(iter: I) -> Option<T>

where I: Iterator<Item = Option<U>>,

Takes each element in the Iterator: if it is a None, no further elements are taken, and the None is returned. Should no None occur, the sum of all elements is returned.

Examples

This sums up the position of the character ‘a’ in a vector of strings, if a word did not have the character ‘a’ the operation returns None:

let words = vec!["have", "a", "great", "day"];
let total: Option<usize> = words.iter().map(|w| w.find('a')).sum();
assert_eq!(total, Some(5));
let words = vec!["have", "a", "good", "day"];
let total: Option<usize> = words.iter().map(|w| w.find('a')).sum();
assert_eq!(total, None);

impl<T> ToPyObject for Option<T>

where T: ToPyObject,

Option::Some<T> is converted like T. Option::None is converted to Python None.

fn to_object(&self, py: Python<'_>) -> Py<PyAny>

👎Deprecated since 0.23.0: ToPyObject is going to be replaced by IntoPyObject. See the migration guide (https://pyo3.rs/v0.23.0/migration) for more information.

Converts self into a Python object.

impl<T> Try for Option<T>

type Output = T

🔬This is a nightly-only experimental API. (try_trait_v2)

The type of the value produced by ? when not short-circuiting.

type Residual = Option<Infallible>

🔬This is a nightly-only experimental API. (try_trait_v2)

The type of the value passed to FromResidual::from_residual as part of ? when short-circuiting.

fn from_output(output: <Option<T> as Try>::Output) -> Option<T>

🔬This is a nightly-only experimental API. (try_trait_v2)

Constructs the type from its Output type.

fn branch( self, ) -> ControlFlow<<Option<T> as Try>::Residual, <Option<T> as Try>::Output>

🔬This is a nightly-only experimental API. (try_trait_v2)

Used in ? to decide whether the operator should produce a value (because this returned ControlFlow::Continue) or propagate a value back to the caller (because this returned ControlFlow::Break).

impl<T> UnwrapThrowExt<T> for Option<T>

fn unwrap_throw(self) -> T

Unwrap this Option or Result, but instead of panicking on failure, throw an exception to JavaScript.

fn expect_throw(self, message: &str) -> T

Unwrap this container’s T value, or throw an error to JS with the given message if the T value is unavailable (e.g. an Option<T> is None).

impl<T> Value for Option<T>

where T: Value,

fn record(&self, key: &Field, visitor: &mut dyn Visit)

Visits this value with the given Visitor.

impl<T> WasmAbi for Option<T>

where T: WasmAbi<Prim4 = ()>,

type Prim1 = u32

Whether this Option is a Some value.

type Prim2 = <T as WasmAbi>::Prim1

type Prim3 = <T as WasmAbi>::Prim2

type Prim4 = <T as WasmAbi>::Prim3

fn split( self, ) -> (u32, <T as WasmAbi>::Prim1, <T as WasmAbi>::Prim2, <T as WasmAbi>::Prim3)

Splits this type up into primitives to be sent over the ABI.

fn join( is_some: u32, prim1: <T as WasmAbi>::Prim1, prim2: <T as WasmAbi>::Prim2, prim3: <T as WasmAbi>::Prim3, ) -> Option<T>

Reconstructs this type from primitives received over the ABI.

impl<T> Zeroable for Option<T>

where T: ZeroableInOption,

fn zeroed() -> Self

Calls zeroed.

impl<T> Copy for Option<T>

where T: Copy,

impl<T> Eq for Option<T>

where T: Eq,

impl<T> Pod for Option<T>

where T: PodInOption,

impl<T> StructuralPartialEq for Option<T>