# actix_web::http::header::Entry - Rust
API documentation for the Rust `Entry` enum in crate `actix_web`.
Keywords: rust, rustlang, rust-lang, Entry

# [−] [src] Enum actix_web::http::header::Entry

    pub enum Entry<'a, T> where
        T: 'a + '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

## Methods

###

`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)
            .expect("valid header names")
            .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").unwrap()
        .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")
        .expect("host is a valid string")
        .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").unwrap().key(), "x-hello");

## Trait Implementations

###

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

[src]

####

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

[src]

Formats the value using the given formatter. Read more

## Auto Trait Implementations

###

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

###

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

## Blanket Implementations

###

`impl<T> From for T`

[src]

####

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

[src]

Performs the conversion.

###

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

[src]

####

`fn into(self) -> U`

[src]

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>`

[src]

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

Performs the conversion.

###

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

[src]

####

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

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Immutably borrows from an owned value. Read more

###

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

[src]

####

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

[src]

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,`

[src]

####

`fn get_type_id(&self) -> TypeId`

[src]

🔬 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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