Struct Map

pub struct Map<K, V> { /* private fields */ }

Represents a JSON key/value type.

Implementations

impl Map<String, Value>

pub fn new() -> Self

Makes a new empty Map.

pub fn with_capacity(capacity: usize) -> Self

Makes a new empty Map with the given initial capacity.

pub fn clear(&mut self)

Clears the map, removing all values.

pub fn get<Q>(&self, key: &Q) -> Option<&Value>

where String: Borrow<Q>, Q: ?Sized + Ord + Eq + Hash,

Returns a reference to the value corresponding to the key.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

pub fn contains_key<Q>(&self, key: &Q) -> bool

where String: Borrow<Q>, Q: ?Sized + Ord + Eq + Hash,

Returns true if the map contains a value for the specified key.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

pub fn get_mut<Q>(&mut self, key: &Q) -> Option<&mut Value>

where String: Borrow<Q>, Q: ?Sized + Ord + Eq + Hash,

Returns a mutable reference to the value corresponding to the key.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

pub fn get_key_value<Q>(&self, key: &Q) -> Option<(&String, &Value)>

where String: Borrow<Q>, Q: ?Sized + Ord + Eq + Hash,

Returns the key-value pair matching the given key.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

pub fn insert(&mut self, k: String, v: Value) -> Option<Value>

Inserts a key-value pair into the map.

If the map did not have this key present, None is returned.

If the map did have this key present, the value is updated, and the old value is returned.

pub fn remove<Q>(&mut self, key: &Q) -> Option<Value>

where String: Borrow<Q>, Q: ?Sized + Ord + Eq + Hash,

Removes a key from the map, returning the value at the key if the key was previously in the map.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

If serde_json’s “preserve_order” is enabled, .remove(key) is equivalent to [.swap_remove(key)][Self::swap_remove], replacing this entry’s position with the last element. If you need to preserve the relative order of the keys in the map, use [.shift_remove(key)][Self::shift_remove] instead.

pub fn remove_entry<Q>(&mut self, key: &Q) -> Option<(String, Value)>

where String: Borrow<Q>, Q: ?Sized + Ord + Eq + Hash,

Removes a key from the map, returning the stored key and value if the key was previously in the map.

The key may be any borrowed form of the map’s key type, but the ordering on the borrowed form must match the ordering on the key type.

If serde_json’s “preserve_order” is enabled, .remove_entry(key) is equivalent to [.swap_remove_entry(key)][Self::swap_remove_entry], replacing this entry’s position with the last element. If you need to preserve the relative order of the keys in the map, use [.shift_remove_entry(key)][Self::shift_remove_entry] instead.

pub fn append(&mut self, other: &mut Self)

Moves all elements from other into self, leaving other empty.

pub fn entry<S>(&mut self, key: S) -> Entry<'_>

where S: Into<String>,

Gets the given key’s corresponding entry in the map for in-place manipulation.

pub fn len(&self) -> usize

Returns the number of elements in the map.

pub fn is_empty(&self) -> bool

Returns true if the map contains no elements.

pub fn iter(&self) -> Iter<'_>

Gets an iterator over the entries of the map.

pub fn iter_mut(&mut self) -> IterMut<'_>

Gets a mutable iterator over the entries of the map.

pub fn keys(&self) -> Keys<'_>

Gets an iterator over the keys of the map.

pub fn values(&self) -> Values<'_>

Gets an iterator over the values of the map.

pub fn values_mut(&mut self) -> ValuesMut<'_>

Gets an iterator over mutable values of the map.

pub fn retain<F>(&mut self, f: F)

where F: FnMut(&String, &mut Value) -> bool,

Retains only the elements specified by the predicate.

In other words, remove all pairs (k, v) such that f(&k, &mut v) returns false.

Trait Implementations

impl Clone for Map<String, Value>

fn clone(&self) -> Self

Returns a copy of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Map<String, Value>

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

Formats the value using the given formatter.

impl Default for Map<String, Value>

fn default() -> Self

Returns the “default value” for a type.

impl<'de> Deserialize<'de> for Map<String, Value>

fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>

where D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl Extend<(String, Value)> for Map<String, Value>

fn extend<T>(&mut self, iter: T)

where T: IntoIterator<Item = (String, Value)>,

Extends a collection with the contents of an iterator.

fn extend_one(&mut self, item: A)

🔬This is a nightly-only experimental API. (extend_one)

Extends a collection with exactly one element.

fn extend_reserve(&mut self, additional: usize)

🔬This is a nightly-only experimental API. (extend_one)

Reserves capacity in a collection for the given number of additional elements.

impl From<Map<String, Value>> for Value

fn from(f: Map<String, Value>) -> Self

Convert map (with string keys) to Value::Object.

Examples

use serde_json::{Map, Value};

let mut m = Map::new();
m.insert("Lorem".to_string(), "ipsum".into());
let x: Value = m.into();

impl FromIterator<(String, Value)> for Map<String, Value>

fn from_iter<T>(iter: T) -> Self

where T: IntoIterator<Item = (String, Value)>,

Creates a value from an iterator.

impl<'a, Q> Index<&'a Q> for Map<String, Value>

where String: Borrow<Q>, Q: ?Sized + Ord + Eq + Hash,

Access an element of this map. Panics if the given key is not present in the map.

match val {
    Value::String(s) => Some(s.as_str()),
    Value::Array(arr) => arr[0].as_str(),
    Value::Object(map) => map["type"].as_str(),
    _ => None,
}

type Output = Value

The returned type after indexing.

fn index(&self, index: &Q) -> &Value

Performs the indexing (container[index]) operation.

impl<'a, Q> IndexMut<&'a Q> for Map<String, Value>

where String: Borrow<Q>, Q: ?Sized + Ord + Eq + Hash,

Mutably access an element of this map. Panics if the given key is not present in the map.

map["key"] = json!("value");

fn index_mut(&mut self, index: &Q) -> &mut Value

Performs the mutable indexing (container[index]) operation.

impl<'a> IntoIterator for &'a Map<String, Value>

type Item = (&'a String, &'a Value)

The type of the elements being iterated over.

type IntoIter = Iter<'a>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl<'a> IntoIterator for &'a mut Map<String, Value>

type Item = (&'a String, &'a mut Value)

The type of the elements being iterated over.

type IntoIter = IterMut<'a>

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl IntoIterator for Map<String, Value>

type Item = (String, Value)

The type of the elements being iterated over.

type IntoIter = IntoIter

Which kind of iterator are we turning this into?

fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value.

impl PartialEq for Map<String, Value>

fn eq(&self, other: &Self) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for Map<String, Value>

fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>

where S: Serializer,

Serialize this value into the given Serde serializer.

impl Eq for Map<String, Value>