Eliminating forced downcasts

Question

I am using swiftlint as a way to code better, and for the most part I have been able to muddle my way through up to the following code which includes a forced downcast:

let questionToAdd = MultipleChoiceQuestion(question: dictionary["Question"] as! String,
            correctAnswer: dictionary["CorrectAnswer"] as! String,
            answers: dictionary["Answers"] as! [String])
           questions.append(questionToAdd)

I have been unable to remove the forced unwrapping. Any suggestions would be greatly appreciated. I have tried used the ELSE { return } but that isn't working either, could be the way I had it structured..nonetheless any help or point me in the right direction would be appreciated.

SwiftLint is a nitpicker. There is more than black and white. Force unwrapping is not evil per se. For example if the data is local (a property list or JSON file in the bundle) it cannot be modified and it's 100% safe to force unwrap the values. As mentioned in the answer the best way is to `decode` the data into `MultipleChoiceQuestion` directly. — vadian, Feb 16 '20 at 06:02
Agreed Vadian. I am using a property list within the app it self. At some point we'll move it to firebase in which case its no longer an issue. — Douglas W. Palme, Feb 17 '20 at 01:05

Jon Shier · Accepted Answer · 2020-02-16T04:56:38.917

1

The alternative to forced cast is an optional cast using as?. Typically you'd unwrap the results of those casts and then use the values, like this:

guard let question = dictionary["Question"] as? String, 
    let answer = dictionary["CorrectAnswer"] as? String,
    let answers = dictionary["Answers"] as? [String] else { return }

questions.append(MultipleChoiceQuestion(question: question, answer: answer, answers: answers))

However, since it looks like you're decoding something like JSON, a better choice would be to implement Decodable for your MultipleChoiceQuestion type do this transform for you.

edited Feb 16 '20 at 04:56

answered Feb 16 '20 at 00:31

Jon Shier

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I'll take a look at Decodable and respond. – Douglas W. Palme Feb 16 '20 at 02:28
Btw, I neglected to mention it's not JSON but a dictionary set. What you gave at the top still throws some errors: closure expression not used. – Douglas W. Palme Feb 16 '20 at 03:51
I tried it again, and now I'm getting: Non-void function should return a value – Douglas W. Palme Feb 16 '20 at 04:20
Yes, you'll need to integrate this example into your actual code. Since you only provided an excerpt in your question, I only provided a rough equivalent here. – Jon Shier Feb 16 '20 at 04:56
It was the return, I figured it out last night late and got it working. Thanks Jon. else { throw LoaderError.dictionaryFailed } – Douglas W. Palme Feb 16 '20 at 17:37

Eliminating forced downcasts

1 Answers1