In Swift, an enumeration defines a common type for related values and enables us to work with those values in a type-safe way. Values provided for each enumeration member can be a String, Character, Integer, or any floating-point type.

The following example presents a simple definition of an enum:

enum MLSTeam { 
    case montreal 
    case toronto 
    case newYork 
    case columbus 
    case losAngeles 
    case seattle 
} 

let theTeam = MLSTeam.montreal 

enum MLSTeam provides options for MLS teams. We can choose only one of the options each time; in our example, montreal is chosen.

Multiple cases can be defined and separated by a comma on a single line:

enum MLSTeam { 
    case montreal, toronto, newYork, columbus, lA, seattle 
} 
var theTeam = MLSTeam.montreal 

The type of theTeam is inferred when it is initialized with MLSTeam.montreal. As theTeam is already defined, we can change it with a shorter syntax as follows:

theTeam = .newYork 

In Swift, enums are very powerful sum types that can have associated and raw values. We will look into these concepts in the upcoming sections of this chapter.