Associating values

Enums can also contain associated values. In our scenario, we can leverage this to represent a dimmer. A dimmer changes the intensity of the light, so we can represent it with a third member-the dimmed member:

enum State: Equatable {
    case on
    case off
    case dimmed(value: Double)
}

You may have noticed that we needed to add the Equatable conformance. This is required, as otherwise, the compiler can't synthesize equality anymore without our hint. This implementation works, but we lack a few things. First, not all Double values are valid; we'd probably like to keep these in a reasonable span (between 0 and 1, for example). But perhaps not all of our lights support such values between 0 and 1. Others may want to support between 0 and a 100 or integers between 0 and 255.