---
title: ExpressibleByDictionaryLiteral
framework: swift
role: symbol
role_heading: Protocol
path: swift/expressiblebydictionaryliteral
---

# ExpressibleByDictionaryLiteral

A type that can be initialized using a dictionary literal.

## Declaration

```swift
protocol ExpressibleByDictionaryLiteral
```

## Overview

Overview A dictionary literal is a simple way of writing a list of key-value pairs. You write each key-value pair with a colon (:) separating the key and the value. The dictionary literal is made up of one or more key-value pairs, separated by commas and surrounded with square brackets. To declare a dictionary, assign a dictionary literal to a variable or constant: let countryCodes = ["BR": "Brazil", "GH": "Ghana",                     "JP": "Japan", "US": "United States"] // 'countryCodes' has type '[String: String]'

print(countryCodes["BR"]!) // Prints "Brazil" When the context provides enough type information, you can use a special form of the dictionary literal, square brackets surrounding a single colon, to initialize an empty dictionary. var frequencies: [String: Int] = [:] print(frequencies.count) // Prints "0" note: A dictionary literal is not the same as an instance of Dictionary. You can’t initialize a type that conforms to ExpressibleByDictionaryLiteral simply by assigning an instance of Dictionary, KeyValuePairs, or similar. Conforming to the ExpressibleByDictionaryLiteral Protocol To add the capability to be initialized with a dictionary literal to your own custom types, declare an init(dictionaryLiteral:) initializer. The following example shows the dictionary literal initializer for a hypothetical CountedSet type, which uses setlike semantics while keeping track of the count for duplicate elements: struct CountedSet<Element: Hashable>: Collection, SetAlgebra {     // implementation details

/// Updates the count stored in the set for the given element,     /// adding the element if necessary.     ///     /// - Parameter n: The new count for `element`. `n` must be greater     ///   than or equal to zero.     /// - Parameter element: The element to set the new count on.     mutating func updateCount(_ n: Int, for element: Element) }

extension CountedSet: ExpressibleByDictionaryLiteral {     init(dictionaryLiteral elements: (Element, Int)...) {         self.init()         for (element, count) in elements {             self.updateCount(count, for: element)         }     } }

## Topics

### Associated Types

- [Key](swift/expressiblebydictionaryliteral/key.md)
- [Value](swift/expressiblebydictionaryliteral/value.md)

### Initializers

- [init(dictionaryLiteral:)](swift/expressiblebydictionaryliteral/init(dictionaryliteral:).md)

## Relationships

### Conforming Types

- [Dictionary](swift/dictionary.md)
- [KeyValuePairs](swift/keyvaluepairs.md)

## See Also

### Collection Literals

- [ExpressibleByArrayLiteral](swift/expressiblebyarrayliteral.md)