Enums in the Standard Library

Before we go on and explore various use cases for enums in your projects, it might be tempting to see some of the enums being used in the Swift standard library, so let's have a look.

Bit The Bit enum can have two possible values, One, and Zero. It is used as the Index type for CollectionOfOne<T>.

FloatingPointClassification This enum defines the set of possible IEEE 754 "classes", like NegativeInfinity, PositiveZero, or SignalingNaN.

Mirror.AncestorRepresentation, and Mirror.DisplayStyle These two are used in the context of the Swift Reflection API.

Optional Not much to say here

Process The Process enum contains the command line arguments of the current process (Process.argc, Process.arguments). This is a particularly interesting enum as it used to be a struct in Swift 1.0.