Return non-optional with .Success enum in Swift

Question

Question:

How do I define a function in a way that enforces a non-optional type to be passed when an enum that is also being passed in is of type .Success ? If this can't be done, what's the best way to model this?

Context:

I'm making completion handler based wrapper around our API. The parameters that are passed back to the handler include an enum that gives a response status and a User instance. The enum is something like this:

enum ResponseStatus : Int {
    case Success                    = 200
    case InvalidParameters          = 422
    // and a few more
}

The method signature is like this:

static func createAccount(email: String, password: String, handler: (status: ResponseStatus, user: User?) -> ())

The problem with this is that .Success could be returned along with nil for the user, which shouldn't be able to happen.

I want to be able to enforce that if .Success is passed, user cannot be nil . Can this be done? If not, what's the best way to manage it?

Thanks in advance for help.

Great answers from both @AlexsanderAkers and @neilkimmett. The only thing that separates them is Alex answered mere moments before Neil. Thanks both!

Answer 1

What about something like this?

enum ResponseStatus<T> {
    case Success(T)
    case InvalidParameters
    // other cases
}

Or you could have an Either / Result type and only use the enum for the error scenarios?

static func createAccount(email: String, password: String, handler: (Result<User, ResponseError>) -> Void) { ... }

Answer 2

似乎是https://github.com/antitypical/Result的完美用例