Enum Entry

pub enum Entry<'a, T, S> {
    Occupied(OccupiedEntry<'a, T, S>),
    Vacant(VacantEntry<'a, T, S>),
}

🔬This is a nightly-only experimental API. (hash_set_entry #60896)

Available on crate feature map only.

A view into a single entry in a set, which may either be vacant or occupied.

This enum is constructed from the entry method on HashSet.

Examples

#![feature(hash_set_entry)]

use std::collections::hash_set::HashSet;

let mut set = HashSet::new();
set.extend(["a", "b", "c"]);
assert_eq!(set.len(), 3);

// Existing value (insert)
let entry = set.entry("a");
let _raw_o = entry.insert();
assert_eq!(set.len(), 3);
// Nonexistent value (insert)
set.entry("d").insert();

// Existing value (or_insert)
set.entry("b").or_insert();
// Nonexistent value (or_insert)
set.entry("e").or_insert();

println!("Our HashSet: {:?}", set);

let mut vec: Vec<_> = set.iter().copied().collect();
// The `Iter` iterator produces items in arbitrary order, so the
// items must be sorted to test them against a sorted array.
vec.sort_unstable();
assert_eq!(vec, ["a", "b", "c", "d", "e"]);

Variants

Occupied(OccupiedEntry<'a, T, S>)

🔬This is a nightly-only experimental API. (hash_set_entry #60896)

An occupied entry.

Examples

#![feature(hash_set_entry)]

use std::collections::hash_set::{Entry, HashSet};

let mut set = HashSet::from(["a", "b"]);

match set.entry("a") {
    Entry::Vacant(_) => unreachable!(),
    Entry::Occupied(_) => { }
}

Vacant(VacantEntry<'a, T, S>)

🔬This is a nightly-only experimental API. (hash_set_entry #60896)

A vacant entry.

Examples

#![feature(hash_set_entry)]

use std::collections::hash_set::{Entry, HashSet};

let mut set = HashSet::new();

match set.entry("a") {
    Entry::Occupied(_) => unreachable!(),
    Entry::Vacant(_) => { }
}

Implementations

impl<'a, T, S> Entry<'a, T, S>

pub fn insert(self) -> OccupiedEntry<'a, T, S>

where T: Hash, S: BuildHasher,

🔬This is a nightly-only experimental API. (hash_set_entry #60896)

Sets the value of the entry, and returns an OccupiedEntry.

Examples

#![feature(hash_set_entry)]

use std::collections::HashSet;

let mut set = HashSet::new();
let entry = set.entry("horseyland").insert();

assert_eq!(entry.get(), &"horseyland");

pub fn or_insert(self)

where T: Hash, S: BuildHasher,

🔬This is a nightly-only experimental API. (hash_set_entry #60896)

Ensures a value is in the entry by inserting if it was vacant.

Examples

#![feature(hash_set_entry)]

use std::collections::HashSet;

let mut set = HashSet::new();

// nonexistent key
set.entry("poneyland").or_insert();
assert!(set.contains("poneyland"));

// existing key
set.entry("poneyland").or_insert();
assert!(set.contains("poneyland"));
assert_eq!(set.len(), 1);

pub fn get(&self) -> &T

🔬This is a nightly-only experimental API. (hash_set_entry #60896)

Returns a reference to this entry’s value.

Examples

#![feature(hash_set_entry)]

use std::collections::HashSet;

let mut set = HashSet::new();
set.entry("poneyland").or_insert();

// existing key
assert_eq!(set.entry("poneyland").get(), &"poneyland");
// nonexistent key
assert_eq!(set.entry("horseland").get(), &"horseland");

Trait Implementations

impl<T, S> Debug for Entry<'_, T, S>

where T: Debug,

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

Formats the value using the given formatter.

Layout

Note: Unable to compute type layout, possibly due to this type having generic parameters. Layout can only be computed for concrete, fully-instantiated types.