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iOS Swift Enums and Structs Enums Associated Values

Posted by Daan van Klinken
Daan van Klinken
1,744 Points

Why doesn't this Switch statement use a *default* case?

The Switch statement in the example only uses two cases. Doesn't it always need a default case? So in this example it would be case .Failure: and default: ...

Example from the video:

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

let downloadStatus = Status.Failure("Network connection unavailable")

switch downloadStatus {
case .Success(let success):
    println(success)
case .Failure(let failure):
    println(failure)
}
Daan van Klinken
Daan van Klinken
1,744 Points

Update. found the answer:

https://teamtreehouse.com/forum/is-a-default-case-necessary-in-a-method

If the Switch statement covers all the items already, you don't need to specify a default, if you leave some enum items unspecified, you need to add a default.

1 Answer

J.D. Sandifer
J.D. Sandifer
18,813 Points
J.D. Sandifer
J.D. Sandifer
18,813 Points

This is a great question!

Every switch statement does indeed need to be exhaustive - that is, it must have a case for every possible value. Sometimes, this in ensured by having a default case to catch any unexpected values. However, for this enum where all possible values are defined in the code, it's easy to know that we're catching every possible value in the switch statement.