# Enum Entry

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    pub enum Entry<'a, T, A: Allocator + Clone = Global> {
        Occupied(OccupiedEntry<'a, T, A>),
        Vacant(VacantEntry<'a, T, A>),
    }

🔬This is a nightly-only experimental API. (`btree_set_entry` #133549)
Expand description

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 `BTreeSet`.

## §Examples

    #![feature(btree_set_entry)]

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

    let mut set = BTreeSet::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 BTreeSet: {:?}", set);
    assert!(set.iter().eq(&["a", "b", "c", "d", "e"]));

## Variants§

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### Occupied(OccupiedEntry<'a, T, A>)

🔬This is a nightly-only experimental API. (`btree_set_entry` #133549)

An occupied entry.

#### §Examples

    #![feature(btree_set_entry)]

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

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

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

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### Vacant(VacantEntry<'a, T, A>)

🔬This is a nightly-only experimental API. (`btree_set_entry` #133549)

A vacant entry.

#### §Examples

    #![feature(btree_set_entry)]

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

    let mut set = BTreeSet::new();

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

## Implementations§

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### impl<'a, T: Ord, A: Allocator + Clone> Entry<'a, T, A>

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

🔬This is a nightly-only experimental API. (`btree_set_entry` #133549)

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

##### §Examples

    #![feature(btree_set_entry)]

    use std::collections::BTreeSet;

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

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

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#### pub fn or_insert(self)

🔬This is a nightly-only experimental API. (`btree_set_entry` #133549)

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

##### §Examples

    #![feature(btree_set_entry)]

    use std::collections::BTreeSet;

    let mut set = BTreeSet::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);

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#### pub fn get(&self) -> &T

🔬This is a nightly-only experimental API. (`btree_set_entry` #133549)

Returns a reference to this entry’s value.

##### §Examples

    #![feature(btree_set_entry)]

    use std::collections::BTreeSet;

    let mut set = BTreeSet::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§

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### impl<T: Debug + Ord, A: Allocator + Clone> Debug for Entry<'_, T, A>

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

Formats the value using the given formatter. Read more

## Auto Trait Implementations§

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### impl<'a, T, A> Freeze for Entry<'a, T, A>
where A: Freeze, T: Freeze,

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### impl<'a, T, A> RefUnwindSafe for Entry<'a, T, A>
where A: RefUnwindSafe, T: RefUnwindSafe,

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### impl<'a, T, A> Send for Entry<'a, T, A>
where A: Send, T: Send,

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### impl<'a, T, A> Sync for Entry<'a, T, A>
where A: Sync, T: Sync,

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### impl<'a, T, A> Unpin for Entry<'a, T, A>
where A: Unpin, T: Unpin,

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### impl<'a, T, A = Global> !UnwindSafe for Entry<'a, T, A>

## Blanket Implementations§

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### impl<T> Any for T
where T: 'static + ?Sized,

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#### fn type_id(&self) -> TypeId

Gets the `TypeId` of `self`. Read more
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### impl<T> Borrow<T> for T
where T: ?Sized,

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#### fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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### impl<T> BorrowMut<T> for T
where T: ?Sized,

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#### fn borrow_mut(&mut self) -> &mut T

Mutably borrows from an owned value. Read more
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### impl<T> From<T> for T

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#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T
where U: From<T>,

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#### fn into(self) -> U

Calls `U::from(self)`.

That is, this conversion is whatever the implementation of `From<T> for U` chooses to do.

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### impl<T, U> TryFrom<U> for T
where U: Into<T>,

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#### type Error = Infallible

The type returned in the event of a conversion error.
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#### fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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### impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.
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#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.