# Enum reqwest::header::Entry [−] [src]

    pub enum Entry<'a, T> where
        T: 'a,  {
        Occupied(OccupiedEntry<'a, T>),
        Vacant(VacantEntry<'a, T>),
    }

A view into a single location in a `HeaderMap`, which may be vacant or occupied.

## Variants

`Occupied(OccupiedEntry<'a, T>)`

An occupied entry

`Vacant(VacantEntry<'a, T>)`

A vacant entry

## Implementations

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

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

Ensures a value is in the entry by inserting the default if empty.

Returns a mutable reference to the first value in the entry.

# Examples

    let mut map: HeaderMap<u32> = HeaderMap::default();

    let headers = &[
        "content-length",
        "x-hello",
        "Content-Length",
        "x-world",
    ];

    for &header in headers {
        let counter = map.entry(header)
            .or_insert(0);
        *counter += 1;
    }

    assert_eq!(map["content-length"], 2);
    assert_eq!(map["x-hello"], 1);

#### `pub fn or_insert_with<F>(self, default: F) -> &'a mut T where
F: FnOnce() -> T,` [src]

Ensures a value is in the entry by inserting the result of the default function if empty.

The default function is not called if the entry exists in the map. Returns a mutable reference to the first value in the entry.

# Examples

Basic usage.

    let mut map = HeaderMap::new();

    let res = map.entry("x-hello")
        .or_insert_with(|| "world".parse().unwrap());

    assert_eq!(res, "world");

The default function is not called if the entry exists in the map.

    let mut map = HeaderMap::new();
    map.insert(HOST, "world".parse().unwrap());

    let res = map.entry("host")
        .or_insert_with(|| unreachable!());

    assert_eq!(res, "world");

#### `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(), "x-hello");

## Trait Implementations

### `impl<'a, T> Debug for Entry<'a, T> where
T: 'a + 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 Entry<'a, T> where
T: RefUnwindSafe,`

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

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

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

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