Swift Dictionary API Reference

`Dictionary`

7 methods

A collection whose elements are key-value pairs. A value type bridged to NSDictionary.

Dictionary subscript [Key] -> Value?

Accesses the value associated with the given key, returning nil if the key is not present.

Returns

Value?

Example

swift

var d: [String: Int] = ["a": 1, "b": 2]
print(d["a"]!)  // 1
print(d["c"])   // nil
d["c"] = 3      // inserts new pair

Dictionary.count -> Int

The number of key-value pairs in the dictionary.

Returns

Int

Example

swift

let d = ["a": 1, "b": 2, "c": 3]
print(d.count)  // 3

Dictionary.keys -> Dictionary.Keys

A collection containing just the keys of the dictionary.

Returns

Dictionary.Keys

Example

swift

let d = ["a": 1, "b": 2]
let keys = Array(d.keys)
// keys == ["a", "b"] (order may vary)

Dictionary.values -> Dictionary.Values

A collection containing just the values of the dictionary.

Returns

Dictionary.Values

Example

swift

let d = ["a": 1, "b": 2]
let values = Array(d.values)
// values == [1, 2] (order may vary)

Dictionary.updateValue(_ value: Value, forKey key: Key) -> Value?

Updates the value for the given key, returning the old value (or nil if key was new).

Parameters

Name	Type	Description
value	Value	New value to set.
key	Key	Key to update.

Returns

Value?

Example

swift

var d = ["a": 1, "b": 2]
let old = d.updateValue(10, forKey: "a")
// old == 1, d["a"] == 10

Dictionary.removeValue(forKey: Key) -> Value?

Removes the given key and its associated value, returning the removed value (or nil).

Parameters

Name	Type	Description
forKey	Key	Key to remove.

Returns

Value?

Example

swift

var d = ["a": 1, "b": 2]
let removed = d.removeValue(forKey: "a")
// removed == 1, d == ["b": 2]

Dictionary.forEach(_ body: ((key: Key, value: Value)) throws -> Void) rethrows

Calls the given closure on each key-value pair in the dictionary.

Parameters

Name	Type	Description
body	((key: Key, value: Value)) -> Void	Closure applied to each pair.

Returns

Void

Example

swift

let d = ["a": 1, "b": 2]
d.forEach { (k, v) in
    print("\(k)=\(v)")
}
// prints:
// a=1
// b=2

All references Next: String