Swift Language Enums Enums with associated values
Example
Enum cases can contain one or more payloads (associated values):
enum Action {
case jump
case kick
case move(distance: Float) // The "move" case has an associated distance
}
The payload must be provided when instantiating the enum value:
performAction(.jump)
performAction(.kick)
performAction(.move(distance: 3.3))
performAction(.move(distance: 0.5))
The switch statement can extract the associated value:
switch action {
case .jump:
...
case .kick:
...
case .move(let distance): // or case let .move(distance):
print("Moving: \(distance)")
}
A single case extraction can be done using if case:
if case .move(let distance) = action {
print("Moving: \(distance)")
}
The guard case syntax can be used for later use extraction:
guard case .move(let distance) = action else {
print("Action is not move")
return
}
Enums with associated values are not Equatable by default. Implementation of the == operator must be done manually:
extension Action: Equatable { }
func ==(lhs: Action, rhs: Action) -> Bool {
switch lhs {
case .jump: if case .jump = rhs { return true }
case .kick: if case .kick = rhs { return true }
case .move(let lhsDistance): if case .move (let rhsDistance) = rhs { return lhsDistance == rhsDistance }
}
return false
}
