# Struct alloc::collections::btree_map::VacantEntry

1.0.0 · source ·

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

Expand description

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

## Implementations§

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

1.10.0 · source

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

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

##### Examples

    use std::collections::BTreeMap;

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

Run
1.12.0 · source

#### pub fn into_key(self) -> K

Take ownership of the key.

##### Examples

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

    let mut map: BTreeMap<&str, usize> = BTreeMap::new();

    if let Entry::Vacant(v) = map.entry("poneyland") {
        v.into_key();
    }

Run
source

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

Sets the value of the entry with the `VacantEntry`’s key, and returns a mutable reference to it.

##### Examples

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

    let mut map: BTreeMap<&str, u32> = BTreeMap::new();

    if let Entry::Vacant(o) = map.entry("poneyland") {
        o.insert(37);
    }
    assert_eq!(map["poneyland"], 37);

Run

## Trait Implementations§

1.12.0 · source§

### impl<K: Debug + Ord, V, A: Allocator + Clone> Debug for VacantEntry<'_, 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> RefUnwindSafe for VacantEntry<'a, K, V, A>where A: RefUnwindSafe, K: RefUnwindSafe, V: RefUnwindSafe,

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

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

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

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### impl<'a, K, V, A = Global> !UnwindSafe for VacantEntry<'a, K, V, A>

## Blanket Implementations§

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### impl<T> Any for Twhere 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 Twhere 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 Twhere 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 Twhere 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 Twhere 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 Twhere 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.