Struct VacantEntry

pub struct VacantEntry<'a, T, A = Global>
where
    A: Allocator + Clone,
{ /* private fields */ }

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

Available on crate feature alloc only.

A view into a vacant entry in a BTreeSet. It is part of the Entry enum.

Examples

#![feature(btree_set_entry)]

use std::collections::btree_set::{Entry, BTreeSet};

let mut set = BTreeSet::<&str>::new();

let entry_v = match set.entry("a") {
    Entry::Vacant(view) => view,
    Entry::Occupied(_) => unreachable!(),
};
entry_v.insert();
assert!(set.contains("a") && set.len() == 1);

// Nonexistent key (insert)
match set.entry("b") {
    Entry::Vacant(view) => view.insert(),
    Entry::Occupied(_) => unreachable!(),
}
assert!(set.contains("b") && set.len() == 2);

Implementations

impl<'a, T, A> VacantEntry<'a, T, A>

where T: Ord, A: Allocator + Clone,

pub fn get(&self) -> &T

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

Gets a reference to the value that would be used when inserting through the VacantEntry.

Examples

#![feature(btree_set_entry)]

use std::collections::BTreeSet;

let mut set = BTreeSet::new();
assert_eq!(set.entry("poneyland").get(), &"poneyland");

pub fn into_value(self) -> T

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

Take ownership of the value.

Examples

#![feature(btree_set_entry)]

use std::collections::btree_set::{Entry, BTreeSet};

let mut set = BTreeSet::new();

match set.entry("poneyland") {
    Entry::Occupied(_) => panic!(),
    Entry::Vacant(v) => assert_eq!(v.into_value(), "poneyland"),
}

pub fn insert(self)

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

Sets the value of the entry with the VacantEntry’s value.

Examples

#![feature(btree_set_entry)]

use std::collections::BTreeSet;
use std::collections::btree_set::Entry;

let mut set = BTreeSet::new();

if let Entry::Vacant(o) = set.entry("poneyland") {
    o.insert();
}
assert!(set.contains("poneyland"));

Trait Implementations

impl<T, A> Debug for VacantEntry<'_, T, A>

where T: Debug + Ord, A: Allocator + Clone,

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

Formats the value using the given formatter.