OccupiedEntry in alloc::collections::btree_map - Rust
Description: A view into an occupied entry in a `BTreeMap`. It is part of the `Entry` enum.

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## OccupiedEntry

# Struct OccupiedEntry

1.36.0 · Source

    pub struct OccupiedEntry<'a, K, V, A: Allocator + Clone = Global> { /* private fields */ }

Expand description

A view into an occupied entry in a `BTreeMap`. It is part of the `Entry` enum.

## Implementations§

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### impl<'a, K: Ord, V, A: Allocator + Clone> OccupiedEntry<'a, K, V, A>

1.10.0 · Source

#### pub fn key(&self) -> &K

Gets a reference to the key in the entry.

##### §Examples

    use std::collections::BTreeMap;

    let mut map: BTreeMap<&str, usize> = BTreeMap::new();
    map.entry("poneyland").or_insert(12);
    assert_eq!(map.entry("poneyland").key(), &"poneyland");

1.12.0 · Source

#### pub fn remove_entry(self) -> (K, V)

Take ownership of the key and value from the map.

##### §Examples

    use std::collections::BTreeMap;
    use std::collections::btree_map::Entry;

    let mut map: BTreeMap<&str, usize> = BTreeMap::new();
    map.entry("poneyland").or_insert(12);

    if let Entry::Occupied(o) = map.entry("poneyland") {
        // We delete the entry from the map.
        o.remove_entry();
    }

    // If now try to get the value, it will panic:
    // println!("{}", map["poneyland"]);

1.0.0 · Source

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

Gets a reference to the value in the entry.

##### §Examples

    use std::collections::BTreeMap;
    use std::collections::btree_map::Entry;

    let mut map: BTreeMap<&str, usize> = BTreeMap::new();
    map.entry("poneyland").or_insert(12);

    if let Entry::Occupied(o) = map.entry("poneyland") {
        assert_eq!(o.get(), &12);
    }

1.0.0 · Source

#### pub fn get_mut(&mut self) -> &mut V

Gets a mutable reference to the value in the entry.

If you need a reference to the `OccupiedEntry` that may outlive the destruction of the `Entry` value, see `into_mut`.

##### §Examples

    use std::collections::BTreeMap;
    use std::collections::btree_map::Entry;

    let mut map: BTreeMap<&str, usize> = BTreeMap::new();
    map.entry("poneyland").or_insert(12);

    assert_eq!(map["poneyland"], 12);
    if let Entry::Occupied(mut o) = map.entry("poneyland") {
        *o.get_mut() += 10;
        assert_eq!(*o.get(), 22);

        // We can use the same Entry multiple times.
        *o.get_mut() += 2;
    }
    assert_eq!(map["poneyland"], 24);

1.0.0 · Source

#### pub fn into_mut(self) -> &'a mut V

Converts the entry into a mutable reference to its value.

If you need multiple references to the `OccupiedEntry`, see `get_mut`.

##### §Examples

    use std::collections::BTreeMap;
    use std::collections::btree_map::Entry;

    let mut map: BTreeMap<&str, usize> = BTreeMap::new();
    map.entry("poneyland").or_insert(12);

    assert_eq!(map["poneyland"], 12);
    if let Entry::Occupied(o) = map.entry("poneyland") {
        *o.into_mut() += 10;
    }
    assert_eq!(map["poneyland"], 22);

1.0.0 · Source

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

Sets the value of the entry with the `OccupiedEntry`’s key, and returns the entry’s old value.

##### §Examples

    use std::collections::BTreeMap;
    use std::collections::btree_map::Entry;

    let mut map: BTreeMap<&str, usize> = BTreeMap::new();
    map.entry("poneyland").or_insert(12);

    if let Entry::Occupied(mut o) = map.entry("poneyland") {
        assert_eq!(o.insert(15), 12);
    }
    assert_eq!(map["poneyland"], 15);

1.0.0 · Source

#### pub fn remove(self) -> V

Takes the value of the entry out of the map, and returns it.

##### §Examples

    use std::collections::BTreeMap;
    use std::collections::btree_map::Entry;

    let mut map: BTreeMap<&str, usize> = BTreeMap::new();
    map.entry("poneyland").or_insert(12);

    if let Entry::Occupied(o) = map.entry("poneyland") {
        assert_eq!(o.remove(), 12);
    }
    // If we try to get "poneyland"'s value, it'll panic:
    // println!("{}", map["poneyland"]);

## Trait Implementations§

1.12.0 · Source§

### impl<K: Debug + Ord, V: Debug, A: Allocator + Clone> Debug for OccupiedEntry<'_, K, V, 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, K, V, A = Global> !UnwindSafe for OccupiedEntry<'a, K, V, A>

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### impl<'a, K, V, A> Freeze for OccupiedEntry<'a, K, V, A>
where A: Freeze,

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### impl<'a, K, V, A> RefUnwindSafe for OccupiedEntry<'a, K, V, A>
where A: RefUnwindSafe, K: RefUnwindSafe, V: RefUnwindSafe,

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### impl<'a, K, V, A> Send for OccupiedEntry<'a, K, V, A>
where A: Send, K: Send, V: Send,

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### impl<'a, K, V, A> Sync for OccupiedEntry<'a, K, V, A>
where A: Sync, K: Sync, V: Sync,

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### impl<'a, K, V, A> Unpin for OccupiedEntry<'a, K, V, A>
where A: Unpin,

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### impl<'a, K, V, A> UnsafeUnpin for OccupiedEntry<'a, K, V, A>
where A: UnsafeUnpin,

## 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.