Default value optional swift doesnt make it nonOptional

Question

I set a default string value with the ?? operator. But i get an optional String?

    request(.GET, CUSTOMER_URL, parameters: params, encoding: .URL).responseJSON { (request, response, result) -> Void in
        var message = JSON(result.value ?? "")["message"].string ?? "Default value to make it nonOptional"
        switch(result) {
        case .Success(let json):
            if let customer = JSON(json)["customer"].dictionaryObject {
                GlobalCache.sharedInstance.setCustomer(customer)
            }
            completion(succeed: response?.statusCode == 200, message: message)
        case .Failure(_,_):
            completion(succeed: false, message: message)
        }
    }

Expected behaviour

Unexpected behaviour

I know that, my question is why is an optional since i'm providing a default value. Post edited. — Godfather, Sep 15 '15 at 07:34
Is the `JSON` class your custom one or some 3rd party library to take a look at it? — Dmytro Hutsuliak, Sep 15 '15 at 08:04

Dmytro Hutsuliak · Answer 1 · 2015-09-15T08:54:24.227

1

What version of Xcode do you use? I couldn't reproduce specified behaviour in Xcode 7 GM (7A218). If your version is lower it looks like a bug in previous beta.

edited Sep 15 '15 at 08:54

answered Sep 15 '15 at 08:47

Dmytro Hutsuliak

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It's a mysticism... I think we just need a third person to test this case in their 7A218 build. – Dmytro Hutsuliak Sep 15 '15 at 08:58

score 0 · Answer 2 · edited May 23 '17 at 11:44

0

This is similar to Providing a default value for an Optional in Swift?

You can use a type annotation to force a non-optional value:

var message: String = JSON(result.value ?? "")["message"].string ?? "Default value"

edited May 23 '17 at 11:44

Community

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answered Sep 15 '15 at 08:06

Tali

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But again the right side of the question should be evaluated to string not to optional string – Jason Nam Sep 15 '15 at 08:08
did you see my images? – Godfather Sep 15 '15 at 08:11
2

Of course you can, but I don't think that is what is wanted. `Using let optString: String? = nil var message = optString ?? "Default value"` also sets `message` to "Default value" with type `String`. The question is more like, why isn't it without optional, because the ?? operator does that in other contexts as well. – Binarian Sep 15 '15 at 08:12
I don't really see any good reason why the type defaults to `String?` here. My best explanation is that this is a bug in the language. – Tali Sep 15 '15 at 08:50
Or in the particular environment as it showed my test above. – Dmytro Hutsuliak Sep 15 '15 at 09:02

Default value optional swift doesnt make it nonOptional

2 Answers2