Swift enum evaluation

Question

Using Alamofire we're trying to determine if an error is a certain kind of error (response code 499) as represented by a "nested" AFError enum:

    if response.result.isFailure {
        if let aferror = error as? AFError {
            //THIS LINE FAILS 
            if (aferror == AFError.responseValidationFailed(reason: AFError.ResponseValidationFailureReason.unacceptableStatusCode(code: 499))) {
               ....
            }
        }            
    }

But this results in the compiler error:

Binary operator '==' cannot be applied to two 'AFError' operands

How can you do this?

Answer 1

Well, you could trying extending AFEError to conform to Equatable in order to use ==, but you are probably better off using switch and pattern matching:

switch aferror {
    case .responseValidationFailed(let reason) :
        switch reason {
            case AFError.ResponseValidationFailureReason.unacceptableStatusCode(let code):
                if code == 499 { print("do something here") }
            default:
                print("You should handle all inner cases")
        {
    default:
        print("Handle other AFError cases")
}

This is the best syntax to ensure (and get the compiler to help you ensure) that all possible error cases and reasons are handled. If you only want to address a single case, like in your example, you can use the newer if case syntax, like this:

if case .responseValidationFailed(let reason) = aferror, case AFError.ResponseValidationFailureReason.unacceptableStatusCode(let code) = reason, code == 499 {
    print("Your code for this case here")
}