Elaboration on a switch statement for a enum

Question

Hi, so I just recently completed the associated values section of the Swift course and I feel as though the associated values itself is pretty easy to grasp however I'm kinda lost as to what exactly the switch statement is performing on this enum. I get that it's unwrapping the value of .Failure I guess I'm just sort of mixed up on the syntax of the actual switch statement. I'm sorry if this is vague but if someone had the time I'd appreciate a little step by step as to how the switch statement is operating.

enum Status {
    case Success(String)
    case Failure(String)
}

let downloadStatus = Status.Failure("Network Connection Lost")

switch downloadStatus {
case .Success(let success):
    println(success)
case .Failure(let failure):
    println(failure)
}

Answer 1 · 2015-01-15T22:33:11Z

January 15, 2015 10:33pm

Hi Peter,

The switch statement in your above code is actually very simple but the syntax has confused a few other users because of the sudden ability to pass and receive string values via the case statements. To clear up any confusion we can write the same switch using the below code without breaking it.

switch downloadStatus {
case .Success:
    println("Looking good!")
case .Failure:
    println("Something went wrong!")
}

The only difference here is instead of assigning the string values via a constant we're simply checking if downloadStatus matches one of our enum values, Swift has no requirement for us to always request the enum value which would be cumbersome and create ugly code very quickly.

Back to your original code, as I said above this code will execute the same way, the only difference is we're assigning a constant using the string value set when we constructed the enum, one thing that users also get confused by is the naming conventions around this and the secret is you can call them whatever you want as seen below.

switch downloadStatus {
case .Success(let itWasSuccessful):
    println(itWasSuccessful)
case .Failure(let somethingFailed):
    println(somethingFailed)
}

Hope that helps.

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Peter Fuhrey

Peter Fuhrey

Elaboration on a switch statement for a enum

1 Answer

Chris Shaw

Chris Shaw

Peter Fuhrey

Peter Fuhrey