# Struct serde_json::map::Map

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

Expand description

Represents a JSON key/value type.

## Implementations

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### impl Map<String, Value>

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#### pub fn new() -> Self

Makes a new empty Map.

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#### pub fn with_capacity(capacity: usize) -> Self

Makes a new empty Map with the given initial capacity.

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#### pub fn clear(&mut self)

Clears the map, removing all values.

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#### 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.

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#### 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.

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#### 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.

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#### 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.

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#### 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.

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#### 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.

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#### 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.

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

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

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#### 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.

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#### pub fn len(&self) -> usize

Returns the number of elements in the map.

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#### pub fn is_empty(&self) -> bool

Returns true if the map contains no elements.

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#### pub fn iter(&self) -> Iter<'_>ⓘNotable traits for Iter<'a>`impl<'a> Iterator for Iter<'a> type Item = (&'a String, &'a Value);`

Gets an iterator over the entries of the map.

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#### pub fn iter_mut(&mut self) -> IterMut<'_>ⓘNotable traits for IterMut<'a>`impl<'a> Iterator for IterMut<'a> type Item = (&'a String, &'a mut Value);`

Gets a mutable iterator over the entries of the map.

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#### pub fn keys(&self) -> Keys<'_>ⓘNotable traits for Keys<'a>`impl<'a> Iterator for Keys<'a> type Item = &'a String;`

Gets an iterator over the keys of the map.

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#### pub fn values(&self) -> Values<'_>ⓘNotable traits for Values<'a>`impl<'a> Iterator for Values<'a> type Item = &'a Value;`

Gets an iterator over the values of the map.

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#### pub fn values_mut(&mut self) -> ValuesMut<'_>ⓘNotable traits for ValuesMut<'a>`impl<'a> Iterator for ValuesMut<'a> type Item = &'a mut Value;`

Gets an iterator over mutable values of the map.

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#### 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

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### impl Clone for Map<String, Value>

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#### fn clone(&self) -> Self

Returns a copy of the value. Read more

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

Performs copy-assignment from `source`. Read more

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### impl Debug for Map<String, Value>

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

Formats the value using the given formatter. Read more

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### impl Default for Map<String, Value>

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#### fn default() -> Self

Returns the “default value” for a type. Read more

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

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#### fn deserialize<D>(deserializer: D) -> Result<Self, D::Error> where
D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer. Read more

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

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#### fn extend<T>(&mut self, iter: T) where
T: IntoIterator<Item = (String, Value)>,

Extends a collection with the contents of an iterator. Read more

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#### fn extend_one(&mut self, item: A)

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

Extends a collection with exactly one element.

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#### 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. Read more

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

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

Convert map (with string keys) to `Value`

##### Examples

    use serde_json::{Map, Value};

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

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

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#### fn from_iter<T>(iter: T) -> Self where
T: IntoIterator<Item = (String, Value)>,

Creates a value from an iterator. Read more

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### 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.

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

Performs the indexing (`container[index]`) operation. Read more

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### 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");

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

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

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### 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?

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#### fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value. Read more

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### 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?

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#### fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value. Read more

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### 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?

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#### fn into_iter(self) -> Self::IntoIter

Creates an iterator from a value. Read more

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### impl PartialEq<Map<String, Value>> for Map<String, Value>

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

This method tests for `self` and `other` values to be equal, and is used by `==`. Read more

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

This method tests for `!=`.

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### impl Serialize for Map<String, Value>

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

Serialize this value into the given Serde serializer. Read more

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### impl Eq for Map<String, Value>

## Auto Trait Implementations

### impl<K, V> RefUnwindSafe for Map<K, V> where
K: RefUnwindSafe,
V: RefUnwindSafe,

### impl<K, V> Send for Map<K, V> where
K: Send,
V: Send,

### impl<K, V> Sync for Map<K, V> where
K: Sync,
V: Sync,

### impl<K, V> Unpin for Map<K, V>

### impl<K, V> UnwindSafe for Map<K, V> where
K: RefUnwindSafe,
V: RefUnwindSafe,

## 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,

const: unstable · source

#### 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,

const: unstable · source

#### 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

const: unstable · source

#### fn from(t: T) -> T

Returns the argument unchanged.

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### impl<T, U> Into<U> for T where
U: From<T>,

const: unstable · source

#### 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> ToOwned for T where
T: Clone,

#### type Owned = T

The resulting type after obtaining ownership.

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#### fn to_owned(&self) -> T

Creates owned data from borrowed data, usually by cloning. Read more

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#### fn clone_into(&self, target: &mut T)

Uses borrowed data to replace owned data, usually by cloning. Read more

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### impl<T, U> TryFrom<U> for T where
U: Into<T>,

#### type Error = Infallible

The type returned in the event of a conversion error.

const: unstable · source

#### 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>,

#### type Error = <U as TryFrom<T>>::Error

The type returned in the event of a conversion error.

const: unstable · source

#### fn try_into(self) -> Result<U, <U as TryFrom<T>>::Error>

Performs the conversion.

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### impl<T> DeserializeOwned for T where
T: for<'de> Deserialize<'de>,