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");