Swift中调用中缺少参数'coder'的参数

Question

class SecondViewController:UIViewController {
  required init(coder aDecoder: NSCoder){
    super.init(coder: aDecoder)
    //Custom logic here
  }
}

Quite a newbie question:

a view controller(SecondViewController), inherent from UIViewController needs a designated init function like above.

In this case, how should I call it, given I am not sure what the value for "coder" should be? I used to call the controller as: SecondViewController(), but it gives:

Missing argument for parameter 'coder' in call

I understand coder parameter has to be provided, but want to ask what its value comes from.

Answer 1

Thanks for the answers from @Chackle. Finally the solution I figured out is below.

What I want:

• Inherit my SecondViewController from UIViewController
• Simply to initialize any new SecondViewController as SecondViewController()

Solution:

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

    init() {
        super.init(nibName: nil, bundle: nil)
        //Do whatever you want here
    }

"required init(coder aDecoder: NSCoder)" is a must if you create a subclass of UIViewController . And so is "super.init(nibName: nil, bundle: nil)" , because it is the way how UIViewController does initialization.

Answer 2

initWithCoder is a constructor specifically for the Interface Builder. This is the constructor that is called when you create a UIViewController in the interface builder.

You instantiate a view controller via this by using 'segues'. If you do not already know about segues I would recommend checking up on some documentation / tutorials to do with them. It really helps explain things.

This little tutorial teaches you how to use segues correctly and even pass data between View Controllers: http://www.appcoda.com/storyboards-ios-tutorial-pass-data-between-view-controller-with-segue/

EDIT: If you wish to not use segues then perhaps this bit of code might be of some help to you (you still need to create the ViewController in the interface builder however)

let storyboard = UIStoryboard(name: "MyStoryboardName", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier("someViewController") as! UIViewController
self.presentViewController(vc, animated: true, completion: nil)