Struct hashbrown::hash_map::VacantEntryRef

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pub struct VacantEntryRef<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone = Global> { /* private fields */ }
Expand description

A view into a vacant entry in a HashMap. It is part of the EntryRef enum.

§Examples

use hashbrown::hash_map::{EntryRef, HashMap, VacantEntryRef};

let mut map = HashMap::<String, i32>::new();

let entry_v: VacantEntryRef<_, _, _, _> = match map.entry_ref("a") {
    EntryRef::Vacant(view) => view,
    EntryRef::Occupied(_) => unreachable!(),
};
entry_v.insert(10);
assert!(map["a"] == 10 && map.len() == 1);

// Nonexistent key (insert and update)
match map.entry_ref("b") {
    EntryRef::Occupied(_) => unreachable!(),
    EntryRef::Vacant(view) => {
        let value = view.insert(2);
        assert_eq!(*value, 2);
        *value = 20;
    }
}
assert!(map["b"] == 20 && map.len() == 2);

Implementations§

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impl<'a, 'b, K, Q: ?Sized, V, S, A: Allocator + Clone> VacantEntryRef<'a, 'b, K, Q, V, S, A>

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pub fn key(&self) -> &Q
where K: Borrow<Q>,

Gets a reference to the key that would be used when inserting a value through the VacantEntryRef.

§Examples
use hashbrown::HashMap;

let mut map: HashMap<String, u32> = HashMap::new();
let key: &str = "poneyland";
assert_eq!(map.entry_ref(key).key(), "poneyland");
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pub fn into_key(self) -> K
where K: From<&'b Q>,

Take ownership of the key.

§Examples
use hashbrown::hash_map::{EntryRef, HashMap};

let mut map: HashMap<String, u32> = HashMap::new();
let key: &str = "poneyland";

match map.entry_ref(key) {
    EntryRef::Occupied(_) => panic!(),
    EntryRef::Vacant(v) => assert_eq!(v.into_key(), "poneyland".to_owned()),
}
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pub fn insert(self, value: V) -> &'a mut V
where K: Hash + From<&'b Q>, S: BuildHasher,

Sets the value of the entry with the VacantEntryRef’s key, and returns a mutable reference to it.

§Examples
use hashbrown::HashMap;
use hashbrown::hash_map::EntryRef;

let mut map: HashMap<String, u32> = HashMap::new();
let key: &str = "poneyland";

if let EntryRef::Vacant(o) = map.entry_ref(key) {
    o.insert(37);
}
assert_eq!(map["poneyland"], 37);

Trait Implementations§

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impl<K: Borrow<Q>, Q: ?Sized + Debug, V, S, A: Allocator + Clone> Debug for VacantEntryRef<'_, '_, K, Q, V, S, A>

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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, 'b, K, Q, V, S, A> Freeze for VacantEntryRef<'a, 'b, K, Q, V, S, A>
where K: Freeze, Q: ?Sized,

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impl<'a, 'b, K, Q, V, S, A> RefUnwindSafe for VacantEntryRef<'a, 'b, K, Q, V, S, A>

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impl<'a, 'b, K, Q, V, S, A> Send for VacantEntryRef<'a, 'b, K, Q, V, S, A>
where K: Send, Q: Sync + ?Sized, S: Send, A: Send, V: Send,

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impl<'a, 'b, K, Q, V, S, A> Sync for VacantEntryRef<'a, 'b, K, Q, V, S, A>
where K: Sync, Q: Sync + ?Sized, S: Sync, A: Sync, V: Sync,

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impl<'a, 'b, K, Q, V, S, A> Unpin for VacantEntryRef<'a, 'b, K, Q, V, S, A>
where K: Unpin, Q: ?Sized,

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impl<'a, 'b, K, Q, V, S, A = Global> !UnwindSafe for VacantEntryRef<'a, 'b, K, Q, V, S, A>

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.