Custom init for UIViewController in Swift with interface setup in storyboard

Question

I\'m having issue for writing custom init for subclass of UIViewController, basically I want to pass the dependency through the init method for viewController rather than se

Answer 1

One way that I've done this is with a convenience initializer.

class MemeDetailVC : UIViewController {

    convenience init(meme: Meme) {
        self.init()
        self.meme = meme
    }
}

Then you initialize your MemeDetailVC with let memeDetailVC = MemeDetailVC(theMeme)

Apple's documentation on initializers is pretty good, but my personal favorite is the Ray Wenderlich: Initialization in Depth tutorial series which should give you plenty of explanation/examples on your various init options and the "proper" way to do things.

---

EDIT: While you can use a convenience initializer on custom view controllers, everyone is correct in stating that you cannot use custom initializers when initializing from the storyboard or through a storyboard segue.

If your interface is set up in the storyboard and you're creating the controller completely programmatically, then a convenience initializer is probably the easiest way to do what you're trying to do since you don't have to deal with the required init with the NSCoder (which I still don't really understand).

If you're getting your view controller via the storyboard though, then you will need to follow @Caleb Kleveter's answer and cast the view controller into your desired subclass then set the property manually.

Answer 2

As of iOS 13 you can initialize the view controller that resides in a storyboard using: instantiateViewController(identifier:creator:) method on the UIStoryboard instance.

tutorial: https://sarunw.com/posts/better-dependency-injection-for-storyboards-in-ios13/

Answer 3

Correct flow is, call the designated initializer which in this case is the init with nibName,

init(tap: UITapGestureRecognizer)
{
    // Initialise the variables here


    // Call the designated init of ViewController
    super.init(nibName: nil, bundle: nil)

    // Call your Viewcontroller custom methods here

}

Answer 4

Swift 5

You can write custom initializer like this ->

class MyFooClass: UIViewController {

    var foo: Foo?

    init(with foo: Foo) {
        self.foo = foo
        super.init(nibName: nil, bundle: nil)
    }

    public required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)
        self.foo = nil
    }
}

Answer 5

As @Caleb Kleveter has pointed out, we can't use a custom initializer while initialising from a Storyboard.

But, we can solve the problem by using factory/class method which instantiate view controller object from Storyboard and return view controller object. I think this is a pretty cool way.

Note: This is not an exact answer to question rather a workaround to solve the problem.

Make class method, in MemeDetailVC class, as follows:

// Considering your view controller resides in Main.storyboard and it's identifier is set to "MemeDetailVC"
class func `init`(meme: Meme) -> MemeDetailVC? {
    let storyboard = UIStoryboard(name: "Main", bundle: nil)
    let vc = storyboard.instantiateViewController(withIdentifier: "MemeDetailVC") as? MemeDetailVC
    vc?.meme = meme
    return vc
}

Usage:

let memeDetailVC = MemeDetailVC.init(meme: Meme())

Answer 6

You can't use a custom initializer when you initialize from a Storyboard, using init?(coder aDecoder: NSCoder) is how Apple designed the storyboard to initialize a controller. However, there are ways to send data to a UIViewController.

Your view controller's name has detail in it, so I suppose that you get there from a different controller. In this case you can use the prepareForSegue method to send data to the detail (This is Swift 3):

override func prepare(for segue: UIStoryboardSegue, sender: AnyObject?) {
    if segue.identifier == "identifier" {
        if let controller = segue.destinationViewController as? MemeDetailVC {
            controller.meme = "Meme"
        }
    }
}

I just used a property of type String instead of Meme for testing purposes. Also, make sure that you pass in the correct segue identifier ("identifier" was just a placeholder).