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Fixing "Class ViewController has no initializers"

Paul Hudson       @twostraws

This is a common error, and one you can fix in just a few seconds. Swift has very strict rules about property initialization: if you give a class any properties without a default value, you must create an initializer that sets those default values.

There are two ways to solve this problem: either provide a default value for your property when you define the property, or create a custom init() method to set the values.

First, identify the problem property. Look for things like this:

class ViewController: UIViewController {
    var username: String
}

That defines a new property but doesn't give it an initial value, so Swift will refuse to build the app.

The simple solution is just to give your property a sensible initial value when it's defined, like this:

class ViewController: UIViewController {
    var username: String = "Anonymous"
}

The slightly more complicated solution is to create a custom init() method that gives properties default values in one place, then calls super.init(). When working with UIViewController and storyboards, the initializer you will want to override should look like this:

required init?(coder aDecoder: NSCoder) {
    self.username = "Anonymous"
    super.init(coder: aDecoder)
}

Remember: you must initialize all your own properties before calling super.init() or any other methods.

Available from iOS 7.0

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