# Struct reqwest::header::VacantEntry [−] [src]

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

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

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

## Implementations

### `impl<'a, T> VacantEntry<'a, T>` [src]

#### `pub fn key(&self) -> &HeaderName` [src]

Returns a reference to the entry’s key

# Examples

    let mut map = HeaderMap::new();

    assert_eq!(map.entry("x-hello").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") {
        assert_eq!(v.into_key().as_str(), "x-hello");
    }

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

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") {
        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") {
        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: Debug,` [src]

#### `pub fn fmt(&self, f: &mut Formatter<'_>) -> Result<(), Error>` [src]

Formats the value using the given formatter. Read more

## Auto Trait Implementations

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

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

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

### `impl<'a, T> Unpin for VacantEntry<'a, T>`

### `impl<'a, T> !UnwindSafe for VacantEntry<'a, T>`

## Blanket Implementations

### `impl<T> Any for T where
T: 'static + ?Sized,` [src]

#### `pub fn type_id(&self) -> TypeId` [src]

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

### `impl<T> Borrow<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow(&self) -> &T` [src]

Immutably borrows from an owned value. Read more

### `impl<T> BorrowMut<T> for T where
T: ?Sized,` [src]

#### `pub fn borrow_mut(&mut self) -> &mut T` [src]

Mutably borrows from an owned value. Read more

### `impl<T> From<T> for T` [src]

#### `pub fn from(t: T) -> T` [src]

Performs the conversion.

### `impl<T> Instrument for T` [src]

#### `pub fn instrument(self, span: Span) -> Instrumented<Self>` [src]

Instruments this type with the provided `Span`, returning an `Instrumented` wrapper. Read more

#### `pub fn in_current_span(self) -> Instrumented<Self>` [src]

Instruments this type with the current `Span`, returning an `Instrumented` wrapper. Read more

### `impl<T, U> Into<U> for T where
U: From<T>,` [src]

#### `pub fn into(self) -> U` [src]

Performs the conversion.

### `impl<T, U> TryFrom<U> for T where
U: Into<T>,` [src]

#### `type Error = Infallible`

The type returned in the event of a conversion error.

#### `pub fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>` [src]

Performs the conversion.

### `impl<T, U> TryInto<U> for T where
U: TryFrom<T>,` [src]

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

The type returned in the event of a conversion error.

#### `pub fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>` [src]

Performs the conversion.