Custom init for UIViewController in Swift with interface setup in storyboard
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 setting property directly like viewControllerB.property = value
So I made a custom init for my viewController and call super designated init
init(meme: Meme?) {
self.meme = meme
super.init(nibName: nil, bundle: nil)
}
The view controller interface resides in storyboard, I've also make the interface for custom class to be my view controller. And Swift requires to call this init method even if you are not doing anything within this method. Otherwise the compiler will complain...
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
The problem is when I try to call my custom init with MyViewController(meme: meme) it doesn't init properties in my viewController at all...
I was trying to debug, I found in my viewController, init(coder aDecoder: NSCoder) get called first, then my custom init get called later. However these two init method return different self memory addresses.
I'm suspecting something wrong with the init for my viewController, and it will always return self with the init?(coder aDecoder: NSCoder) , which, has no implementation.
Does anyone know how to make custom init for your viewController correctly ? Note: my viewController's interface is set up in storyboard
here is my viewController code:
class MemeDetailVC : UIViewController {
var meme : Meme!
@IBOutlet weak var editedImage: UIImageView!
// TODO: incorrect init
init(meme: Meme?) {
self.meme = meme
super.init(nibName: nil, bundle: nil)
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
override func viewDidLoad() {
/// setup nav title
title = "Detail Meme"
super.viewDidLoad()
}
override func viewWillAppear(animated: Bool) {
super.viewWillAppear(animated)
editedImage = UIImageView(image: meme.editedImage)
}
}
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).
As it was specified in one of the answers above you can not use both and custom init method and storyboard. But you still can use a static method to instantiate ViewController from a storyboard and perform additional setup on it. It will look like this:
class MemeDetailVC : UIViewController {
var meme : Meme!
static func makeMemeDetailVC(meme: Meme) -> MemeDetailVC {
let newViewController = UIStoryboard(name: "Main", bundle: nil).instantiateViewControllerWithIdentifier("IdentifierOfYouViewController") as! MemeDetailVC
newViewController.meme = meme
return newViewController
}
}
Don't forgot to specify IdentifierOfYouViewController as view controller identifier in your storyboard. You may also need to change name of storyboard in the code above.
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.
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