Fatal error: use of unimplemented initializer 'init(coder:)' for class

Question

I decided to continue my remaining project with Swift. When I add the custom class (subclass of UIViewcontroller ) to my storyboard view controller and load the project, the app crashes suddenly with the following error:

fatal error: use of unimplemented initializer 'init(coder:)' for class

This is a code:

import UIKit

class TestViewController: UIViewController {

    init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) {
        super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
        // Custom initialization
    }

    override func viewDidLoad() {
        super.viewDidLoad()
              // Do any additional setup after loading the view.
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }

    /*
    // #pragma mark - Navigation

    // In a storyboard-based application, you will often want to do a little preparation before navigation
    override func prepareForSegue(segue: UIStoryboardSegue?, sender: AnyObject?) {
        // Get the new view controller using [segue destinationViewController].
        // Pass the selected object to the new view controller.
    }
    */
}

Please suggest something

Answer 1

Issue

This is caused by the absence of the initializer init?(coder aDecoder: NSCoder) on the target UIViewController . That method is required because instantiating a UIViewController from a UIStoryboard calls it.

To see how we initialize a UIViewController from a UIStoryboard , please take a look here

Why is this not a problem with Objective-C?

Because Objective-C automatically inherits all the required UIViewController initializers.

Why doesn't Swift automatically inherit the initializers?

Swift by default does not inherit the initializers due to safety. But it will inherit all the initializers from the superclass if all the properties have a value (or optional) and the subclass has not defined any designated initializers.

---

Solution

1. First method

Manually implementing init?(coder aDecoder: NSCoder) on the target UIViewController

required init?(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
}

---

2. Second method

Removing init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) on your target UIViewController will inherit all of the required initializers from the superclass as Dave Wood pointed on his answer below

---

Answer 2

Another option besides @3r1d's is to instead remove the following init method from your class:

init(nibName nibNameOrNil: String?, bundle nibBundleOrNil: NSBundle?) {
    super.init(nibName: nibNameOrNil, bundle: nibBundleOrNil)
    // Custom initialization
}

Including that init method, prevents the sub class from inheriting the init(coder aDecoder: NSCoder!) from its super class. By not including it, your class will inherit both.

Note: See WWDC 2014 Session 403 "Intermediate Swift" at about the 33:50 mark for more details.

Answer 3

For people having the same issue with swift UICollectionViewCells , add the code that @3r1d suggested to your custom UICollectionViewCell class and not to the View Controller:

init(coder aDecoder: NSCoder!)
{
    super.init(coder: aDecoder)
}

Answer 4

For those needing the code in Swift:

required init(coder aDecoder: NSCoder) {
    super.init(coder: aDecoder)
}

[Edit] This was for an older version of Swift. Possibly doesn't work anymore.

Answer 5

I had this problem in a programmatic collectionView cell and even though the op is asking about a vc I still landed on this question when searching for an answer. For me the issue was I did have

required init?(coder aDecoder: NSCoder) {
    fatalError("init(coder:) has not been implemented")
}

implemented so the top answer didn't work. What I didn't have in the cell was the initializer:

// my programmatic cell was missing this
override init(frame: CGRect) {
    super.init(frame: frame)
}

Once I added it the error went away

Answer 6

我不会添加一些方法来使内部机制正常工作，而是将我的属性定义为 @lazy 并在类范围内初始化它们。