Enum hashbrown::map::EntryRef

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pub enum EntryRef<'a, 'b, K, Q: ?Sized, V, S, A = Global>
where A: Allocator,
{ Occupied(OccupiedEntryRef<'a, 'b, K, Q, V, S, A>), Vacant(VacantEntryRef<'a, 'b, K, Q, V, S, A>), }
Expand description

A view into a single entry in a map, which may either be vacant or occupied, with any borrowed form of the map’s key type.

This enum is constructed from the entry_ref method on HashMap.

Hash and Eq on the borrowed form of the map’s key type must match those for the key type. It also require that key may be constructed from the borrowed form through the From trait.

§Examples

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

let mut map = HashMap::new();
map.extend([("a".to_owned(), 10), ("b".into(), 20), ("c".into(), 30)]);
assert_eq!(map.len(), 3);

// Existing key (insert)
let key = String::from("a");
let entry: EntryRef<_, _, _, _> = map.entry_ref(&key);
let _raw_o: OccupiedEntryRef<_, _, _, _> = entry.insert(1);
assert_eq!(map.len(), 3);
// Nonexistent key (insert)
map.entry_ref("d").insert(4);

// Existing key (or_insert)
let v = map.entry_ref("b").or_insert(2);
assert_eq!(std::mem::replace(v, 2), 20);
// Nonexistent key (or_insert)
map.entry_ref("e").or_insert(5);

// Existing key (or_insert_with)
let v = map.entry_ref("c").or_insert_with(|| 3);
assert_eq!(std::mem::replace(v, 3), 30);
// Nonexistent key (or_insert_with)
map.entry_ref("f").or_insert_with(|| 6);

println!("Our HashMap: {:?}", map);

for (key, value) in ["a", "b", "c", "d", "e", "f"].into_iter().zip(1..=6) {
    assert_eq!(map[key], value)
}
assert_eq!(map.len(), 6);

Variants§

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Occupied(OccupiedEntryRef<'a, 'b, K, Q, V, S, A>)

An occupied entry.

§Examples

use hashbrown::hash_map::{EntryRef, HashMap};
let mut map: HashMap<_, _> = [("a".to_owned(), 100), ("b".into(), 200)].into();

match map.entry_ref("a") {
    EntryRef::Vacant(_) => unreachable!(),
    EntryRef::Occupied(_) => { }
}
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Vacant(VacantEntryRef<'a, 'b, K, Q, V, S, A>)

A vacant entry.

§Examples

use hashbrown::hash_map::{EntryRef, HashMap};
let mut map: HashMap<String, i32> = HashMap::new();

match map.entry_ref("a") {
    EntryRef::Occupied(_) => unreachable!(),
    EntryRef::Vacant(_) => { }
}

Implementations§

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

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pub fn insert(self, value: V) -> OccupiedEntryRef<'a, 'b, K, Q, V, S, A>
where K: Hash + From<&'b Q>, S: BuildHasher,

Sets the value of the entry, and returns an OccupiedEntryRef.

§Examples
use hashbrown::HashMap;

let mut map: HashMap<String, u32> = HashMap::new();
let entry = map.entry_ref("horseyland").insert(37);

assert_eq!(entry.key(), "horseyland");
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pub fn or_insert(self, default: V) -> &'a mut V
where K: Hash + From<&'b Q>, S: BuildHasher,

Ensures a value is in the entry by inserting the default if empty, and returns a mutable reference to the value in the entry.

§Examples
use hashbrown::HashMap;

let mut map: HashMap<String, u32> = HashMap::new();

// nonexistent key
map.entry_ref("poneyland").or_insert(3);
assert_eq!(map["poneyland"], 3);

// existing key
*map.entry_ref("poneyland").or_insert(10) *= 2;
assert_eq!(map["poneyland"], 6);
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pub fn or_insert_with<F: FnOnce() -> V>(self, default: F) -> &'a mut V
where K: Hash + From<&'b Q>, S: BuildHasher,

Ensures a value is in the entry by inserting the result of the default function if empty, and returns a mutable reference to the value in the entry.

§Examples
use hashbrown::HashMap;

let mut map: HashMap<String, u32> = HashMap::new();

// nonexistent key
map.entry_ref("poneyland").or_insert_with(|| 3);
assert_eq!(map["poneyland"], 3);

// existing key
*map.entry_ref("poneyland").or_insert_with(|| 10) *= 2;
assert_eq!(map["poneyland"], 6);
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pub fn or_insert_with_key<F: FnOnce(&Q) -> V>(self, default: F) -> &'a mut V
where K: Hash + Borrow<Q> + From<&'b Q>, S: BuildHasher,

Ensures a value is in the entry by inserting, if empty, the result of the default function. This method allows for generating key-derived values for insertion by providing the default function an access to the borrower form of the key.

§Examples
use hashbrown::HashMap;

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

// nonexistent key
map.entry_ref("poneyland").or_insert_with_key(|key| key.chars().count());
assert_eq!(map["poneyland"], 9);

// existing key
*map.entry_ref("poneyland").or_insert_with_key(|key| key.chars().count() * 10) *= 2;
assert_eq!(map["poneyland"], 18);
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pub fn key(&self) -> &Q
where K: Borrow<Q>,

Returns a reference to this entry’s key.

§Examples
use hashbrown::HashMap;

let mut map: HashMap<String, u32> = HashMap::new();
map.entry_ref("poneyland").or_insert(3);
// existing key
assert_eq!(map.entry_ref("poneyland").key(), "poneyland");
// nonexistent key
assert_eq!(map.entry_ref("horseland").key(), "horseland");
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pub fn and_modify<F>(self, f: F) -> Self
where F: FnOnce(&mut V),

Provides in-place mutable access to an occupied entry before any potential inserts into the map.

§Examples
use hashbrown::HashMap;

let mut map: HashMap<String, u32> = HashMap::new();

map.entry_ref("poneyland")
   .and_modify(|e| { *e += 1 })
   .or_insert(42);
assert_eq!(map["poneyland"], 42);

map.entry_ref("poneyland")
   .and_modify(|e| { *e += 1 })
   .or_insert(42);
assert_eq!(map["poneyland"], 43);
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pub fn and_replace_entry_with<F>(self, f: F) -> Self
where F: FnOnce(&K, V) -> Option<V>,

Provides shared access to the key and owned access to the value of an occupied entry and allows to replace or remove it based on the value of the returned option.

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

let mut map: HashMap<String, u32> = HashMap::new();

let entry = map
    .entry_ref("poneyland")
    .and_replace_entry_with(|_k, _v| panic!());

match entry {
    EntryRef::Vacant(e) => {
        assert_eq!(e.key(), "poneyland");
    }
    EntryRef::Occupied(_) => panic!(),
}

map.insert("poneyland".to_string(), 42);

let entry = map
    .entry_ref("poneyland")
    .and_replace_entry_with(|k, v| {
        assert_eq!(k, "poneyland");
        assert_eq!(v, 42);
        Some(v + 1)
    });

match entry {
    EntryRef::Occupied(e) => {
        assert_eq!(e.key(), "poneyland");
        assert_eq!(e.get(), &43);
    }
    EntryRef::Vacant(_) => panic!(),
}

assert_eq!(map["poneyland"], 43);

let entry = map
    .entry_ref("poneyland")
    .and_replace_entry_with(|_k, _v| None);

match entry {
    EntryRef::Vacant(e) => assert_eq!(e.key(), "poneyland"),
    EntryRef::Occupied(_) => panic!(),
}

assert!(!map.contains_key("poneyland"));
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impl<'a, 'b, K, Q: ?Sized, V: Default, S, A: Allocator> EntryRef<'a, 'b, K, Q, V, S, A>

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pub fn or_default(self) -> &'a mut V
where K: Hash + From<&'b Q>, S: BuildHasher,

Ensures a value is in the entry by inserting the default value if empty, and returns a mutable reference to the value in the entry.

§Examples
use hashbrown::HashMap;

let mut map: HashMap<String, Option<u32>> = HashMap::new();

// nonexistent key
map.entry_ref("poneyland").or_default();
assert_eq!(map["poneyland"], None);

map.insert("horseland".to_string(), Some(3));

// existing key
assert_eq!(map.entry_ref("horseland").or_default(), &mut Some(3));

Trait Implementations§

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impl<K: Borrow<Q>, Q: ?Sized + Debug, V: Debug, S, A: Allocator> Debug for EntryRef<'_, '_, 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: ?Sized, V, S, A> Freeze for EntryRef<'a, 'b, K, Q, V, S, A>
where K: Freeze,

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impl<'a, 'b, K, Q: ?Sized, V, S, A> RefUnwindSafe for EntryRef<'a, 'b, K, Q, V, S, A>

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

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

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

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