pub trait FromStr: Sized {
type Err;
// Required method
fn from_str(s: &str) -> Result<Self, Self::Err> ⓘ;
}Expand description
Parse a value from a string
FromStr’s from_str method is often used implicitly, through
str’s parse method. See parse’s documentation for examples.
FromStr does not have a lifetime parameter, and so you can only parse types
that do not contain a lifetime parameter themselves. In other words, you can
parse an i32 with FromStr, but not a &i32. You can parse a struct that
contains an i32, but not one that contains an &i32.
§Examples
Basic implementation of FromStr on an example Point type:
use std::str::FromStr;
#[derive(Debug, PartialEq)]
struct Point {
x: i32,
y: i32
}
#[derive(Debug, PartialEq, Eq)]
struct ParsePointError;
impl FromStr for Point {
type Err = ParsePointError;
fn from_str(s: &str) -> Result<Self, Self::Err> {
let (x, y) = s
.strip_prefix('(')
.and_then(|s| s.strip_suffix(')'))
.and_then(|s| s.split_once(','))
.ok_or(ParsePointError)?;
let x_fromstr = x.parse::<i32>().map_err(|_| ParsePointError)?;
let y_fromstr = y.parse::<i32>().map_err(|_| ParsePointError)?;
Ok(Point { x: x_fromstr, y: y_fromstr })
}
}
let expected = Ok(Point { x: 1, y: 2 });
// Explicit call
assert_eq!(Point::from_str("(1,2)"), expected);
// Implicit calls, through parse
assert_eq!("(1,2)".parse(), expected);
assert_eq!("(1,2)".parse::<Point>(), expected);
// Invalid input string
assert!(Point::from_str("(1 2)").is_err());Required Associated Types§
Required Methods§
1.0.0 · Sourcefn from_str(s: &str) -> Result<Self, Self::Err> ⓘ
fn from_str(s: &str) -> Result<Self, Self::Err> ⓘ
Parses a string s to return a value of this type.
If parsing succeeds, return the value inside Ok, otherwise
when the string is ill-formatted return an error specific to the
inside Err. The error type is specific to the implementation of the trait.
§Examples
Basic usage with i32, a type that implements FromStr:
use std::str::FromStr;
let s = "5";
let x = i32::from_str(s).unwrap();
assert_eq!(5, x);Dyn Compatibility§
This trait is not dyn compatible.
In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.
Implementors§
Source§impl FromStr for devela::_dep::log::LevelFilter
impl FromStr for devela::_dep::log::LevelFilter
type Err = ParseLevelError
Source§impl FromStr for Month
Returns a Month from a string containing either the full month name,
or any of the month ASCII abbreviations.
impl FromStr for Month
Returns a Month from a string containing either the full month name,
or any of the month ASCII abbreviations.
Source§impl FromStr for Weekday
Returns a Weekday from a string containing either the full weekday name,
or any of the weekday ASCII abbreviations.
impl FromStr for Weekday
Returns a Weekday from a string containing either the full weekday name,
or any of the weekday ASCII abbreviations.
1.0.0 · Source§impl FromStr for SocketAddr
impl FromStr for SocketAddr
type Err = AddrParseError
§impl FromStr for Zoned
Parses a zoned timestamp from the Temporal datetime format.
impl FromStr for Zoned
Parses a zoned timestamp from the Temporal datetime format.
See the fmt::temporal for more information on
the precise format.
Note that this is only enabled when the std feature
is enabled because it requires access to a global
TimeZoneDatabase.
§impl FromStr for devela::_dep::tracing::level_filters::LevelFilter
impl FromStr for devela::_dep::tracing::level_filters::LevelFilter
type Err = ParseLevelFilterError
1.5.0 · Source§impl FromStr for SocketAddrV4
impl FromStr for SocketAddrV4
type Err = AddrParseError
1.5.0 · Source§impl FromStr for SocketAddrV6
impl FromStr for SocketAddrV6
type Err = AddrParseError
§impl FromStr for Format
impl FromStr for Format
type Err = Infallible
Source§impl<const CAP: usize> FromStr for ArrayString<CAP>
impl<const CAP: usize> FromStr for ArrayString<CAP>
type Err = CapacityError
Source§impl<const V: i8> FromStr for devela::_info::examples::niche::NonValueI8<V>
Available on doc only.
impl<const V: i8> FromStr for devela::_info::examples::niche::NonValueI8<V>
doc only.