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

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

    pub struct VacantEntry<'a, T> where
        T: '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>`

[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").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");
    }

####
ⓘImportant traits for &'a mut R

### Important traits for &'a mut R

`impl<'a, R> Read for &'a mut R where
R: Read + ?Sized, impl<'a, W> Write for &'a mut W where
W: Write + ?Sized, impl<'a, I> Iterator for &'a mut I where
I: Iterator + ?Sized, type Item = <I as Iterator>::Item;`

`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").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>`

[src]

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,`

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