# [−][src]Struct actix_web::http::header::VacantEntry

    pub struct VacantEntry<'a, T> where
        T: 'a + 'a,  { /* fields omitted */ }

A view into a single empty location in a `HeaderMap`.

This struct is returned as part of the `Entry` enum.

## Methods

###

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

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####

`pub fn key(&self) -> &HeaderName`

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Returns a reference to the entry's key

# Examples

    let mut map = HeaderMap::new();

    assert_eq!(map.entry("x-hello").unwrap().key().as_str(), "x-hello");

####

`pub fn into_key(self) -> HeaderName`

[src]

Take ownership of the key

# Examples

    let mut map = HeaderMap::new();

    if let Entry::Vacant(v) = map.entry("x-hello").unwrap() {
        assert_eq!(v.into_key().as_str(), "x-hello");
    }

####

`pub fn insert(self, value: T) -> &'a mut T`

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Insert the value into the entry.

The value will be associated with this entry's key. A mutable reference to the inserted value will be returned.

# Examples

    let mut map = HeaderMap::new();

    if let Entry::Vacant(v) = map.entry("x-hello").unwrap() {
        v.insert("world".parse().unwrap());
    }

    assert_eq!(map["x-hello"], "world");

####

`pub fn insert_entry(self, value: T) -> OccupiedEntry<'a, T>`

[src]

Insert the value into the entry.

The value will be associated with this entry's key. The new `OccupiedEntry` is returned, allowing for further manipulation.

# Examples

    let mut map = HeaderMap::new();

    if let Entry::Vacant(v) = map.entry("x-hello").unwrap() {
        let mut e = v.insert_entry("world".parse().unwrap());
        e.insert("world2".parse().unwrap());
    }

    assert_eq!(map["x-hello"], "world2");

## Trait Implementations

###

`impl<'a, T> Debug for VacantEntry<'a, T> where T: 'a + Debug,`

[src]

####

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

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Formats the value using the given formatter. Read more

## Auto Trait Implementations

###

`impl<'a, T> Send for VacantEntry<'a, T> where T: Send,`

###

`impl<'a, T> Sync for VacantEntry<'a, T> where T: Sync,`

## Blanket Implementations

###

`impl<T> From for T`

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####

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

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Performs the conversion.

###

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

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####

`fn into(self) -> U`

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Performs the conversion.

###

`impl<T, U> TryFrom for T where T: From<U>,`

[src]

#### `type Error = !`

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

The type returned in the event of a conversion error.

####

`fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>`

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

Performs the conversion.

###

`impl<T> Borrow for T where T: ?Sized,`

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####

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

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Immutably borrows from an owned value. Read more

###

`impl<T> BorrowMut for T where T: ?Sized,`

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####

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

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Mutably borrows from an owned value. Read more

###

`impl<T, U> TryInto for T where U: TryFrom<T>,`

[src]

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

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

The type returned in the event of a conversion error.

####

`fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>`

[src]

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

Performs the conversion.

###

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

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####

`fn get_type_id(&self) -> TypeId`

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

this method will likely be replaced by an associated static

Gets the `TypeId` of `self`. Read more

###

`impl<T> Erased for T`

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