CODEWITHSUNDEEP
ios
Alex Cauthen
Alex Cauthen

Reputation: 517

iOS: unexpectedly found nil while unwrapping an Optional value

Getting the following error:

fatal error: unexpectedly found nil while unwrapping an Optional value

I am making a registration form application. The app allows users to create custom questions to be added to a form. At the moment I'm using a Singleton design pattern to pass the list of questions between the editing tab and the tab used to display the form.

My singleton class: 

class Singleton {
    static let sharedInstance = Singleton()
    var questions: [Question] = []
}

In the editing form the user will press a button to update the form that people can then fill out. Here is that code and is also where I'm getting the error:

var mySingleton: Singleton!

@IBAction func updateForm(sender: AnyObject) {
    for index in mySingleton.questions.count...questionsArray.count {
        mySingleton.questions.append(questionsArray[index])
    }
}

Thank you for your help.

Upvotes: 0

Views: 145

Answers (1)

erdekhayser
erdekhayser

Reputation: 6657

This is where the error is occurring:

for index in mySingleton.questions.count...questionsArray.count {
    mySingleton.questions.append(questionsArray[index])
}

The final index that is looped through is questionsArray.count. When you access questionsArray[questionsArray.count], you are outside the bounds of the array. This index should never be accessed.

Instead, change your loop to the following:

for index in mySingleton.questions.count..<questionsArray.count {
    mySingleton.questions.append(questionsArray[index])
}

The only difference is that ... becomes ..<, in order to leave out the last index that is causing the error.

Edit: after looking back at the code, it seems likely that mySingleton was never set equal to anything. Before this code is executed, you could set mySingleton = Singleton.sharedInstance, or simply get rid of mySingleton and directly use Singleton.sharedInstance.

Upvotes: 2

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