Swift Academy · Lesson

Finite state modeling

Model finite states with enums: represent app flows (loading, success, error), enforce exhaustive handling, and prevent invalid combinations.

Intro

Enums model finite states: a network request might be loading, success, or failure. Nothing else is valid.

A simple enum defines all valid states of a request.

enum RequestState {
    case loading
    case success(data: String)
    case failure(error: String)
}