Mastering Swift 3

Dictionaries

While dictionaries are not as commonly used as arrays, they have an additional functionality that makes them incredibly powerful. A dictionary is a container that stores multiple key-value pairs, where all the keys are of the same type, and all the values are of the same type. The key is used as a unique identifier for the value. A dictionary does not guarantee the order in which the key-value pairs are stored since we look up the values by the key, rather than by the index of the value.

Dictionaries are good for storing items that map to unique identifiers, where the unique identifier should be used to retrieve the item. As an example, countries with their abbreviations are a good example of items that can be stored in a dictionary. ...