Enum Entry

pub enum Entry<'a> {
    Vacant(VacantEntry<'a>),
    Occupied(OccupiedEntry<'a>),
}

A view into a single entry in a map, which may either be vacant or occupied. This enum is constructed from the entry method on Map.

Variants

Vacant(VacantEntry<'a>)

A vacant Entry.

Occupied(OccupiedEntry<'a>)

An occupied Entry.

Implementations

impl<'a> Entry<'a>

pub fn key(&self) -> &String

Returns a reference to this entry’s key.

Examples

let mut map = serde_json::Map::new();
assert_eq!(map.entry("serde").key(), &"serde");

pub fn or_insert(self, default: Value) -> &'a mut Value

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

let mut map = serde_json::Map::new();
map.entry("serde").or_insert(json!(12));

assert_eq!(map["serde"], 12);

pub fn or_insert_with<F>(self, default: F) -> &'a mut Value

where F: FnOnce() -> Value,

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

let mut map = serde_json::Map::new();
map.entry("serde").or_insert_with(|| json!("hoho"));

assert_eq!(map["serde"], "hoho".to_owned());

pub fn and_modify<F>(self, f: F) -> Self

where F: FnOnce(&mut Value),

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

Examples

let mut map = serde_json::Map::new();
map.entry("serde")
    .and_modify(|e| *e = json!("rust"))
    .or_insert(json!("cpp"));

assert_eq!(map["serde"], "cpp");

map.entry("serde")
    .and_modify(|e| *e = json!("rust"))
    .or_insert(json!("cpp"));

assert_eq!(map["serde"], "rust");

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 56 bytes

Size for each variant:

• Vacant: 56 bytes
• Occupied: 40 bytes