Enum http::header::Entry

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

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

Variants§

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Occupied(OccupiedEntry<'a, T>)

An occupied entry

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Vacant(VacantEntry<'a, T>)

A vacant entry

Implementations§

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impl<'a, T> Entry<'a, T>

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pub fn or_insert(self, default: T) -> &'a mut T

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);
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pub fn or_insert_with<F: FnOnce() -> T>(self, default: F) -> &'a mut T

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");
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pub fn key(&self) -> &HeaderName

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§

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

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fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter. Read more

Auto Trait Implementations§

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impl<'a, T> RefUnwindSafe for Entry<'a, T>
where T: RefUnwindSafe,

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

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

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

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impl<'a, T> !UnwindSafe for Entry<'a, T>

Blanket Implementations§

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

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fn type_id(&self) -> TypeId

Gets the TypeId of self. Read more
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impl<T> Borrow<T> for T
where T: ?Sized,

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fn borrow(&self) -> &T

Immutably borrows from an owned value. Read more
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impl<T> BorrowMut<T> for T
where T: ?Sized,

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

Mutably borrows from an owned value. Read more
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impl<T> From<T> for T

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fn from(t: T) -> T

Returns the argument unchanged.

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

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fn into(self) -> U

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

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impl<T, U> TryFrom<U> for T
where U: Into<T>,

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type Error = Infallible

The type returned in the event of a conversion error.
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fn try_from(value: U) -> Result<T, <T as TryFrom<U>>::Error>

Performs the conversion.
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impl<T, U> TryInto<U> for T
where U: TryFrom<T>,

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

The type returned in the event of a conversion error.
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fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.