How can I initialize a variable for UIViewController class in right syntax?

Question

I have a class called UIViewControllerModel which I like to initialize backgroundColor for this class, I am sure this a syntax error, need help for correction please.

class UIViewControllerModel: UIViewController {
    
    var backgroundColor: UIColor 

    required init(backgroundColor: UIColor) {

        super.init()
        self.backgroundColor = backgroundColor

    }

    override func viewDidLoad() {
        
        super.viewDidLoad()
        view.backgroundColor = backgroundColor
 
    }

}

Side comment: please see [ask]. Especially the part where it says in bold: "DO NOT post images of code, data, error messages, etc.". Images of text are not searchable. — Roope, Feb 12 '21 at 10:26
thanks, I was carful about codes, but I did know about errors — ios coder, Feb 12 '21 at 10:34

aheze · Accepted Answer · 2021-02-11T22:53:48.170

4

The required initializer is not the right one -- because your class is a subclass of UIViewController, you need a required init?(coder: NSCoder). You can put your custom initializer that sets backgroundColor in separate init.

Also, instead of viewDidLoad, use loadView for your custom View Controllers that you make in code. This is how you do it:

class UIViewControllerModel: UIViewController {
    
    var backgroundColor: UIColor

    /// Put your custom argument labels here, not inside the `required init?`
    init(backgroundColor: UIColor) {
        self.backgroundColor = backgroundColor
        super.init(nibName: nil, bundle: nil)
    }
    
    /// This is in case the View Controller is loaded from the Storyboard
    required init?(coder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    /// Use this instead of viewDidLoad
    override func loadView() {
        
        /**
         Instantiate the base `view`.
         */
        view = UIView()
        view.backgroundColor = backgroundColor
        
    }

}

let modelVC = UIViewControllerModel(backgroundColor: UIColor.blue)
self.present(modelVC, animated: true)

Result:

View controller with blue background presented

edited Feb 11 '21 at 22:53

answered Feb 11 '21 at 22:48

aheze

24,434
8
68
125

2

could you please explain or update the answer why I should use **loadView** instead **viewDidLoad**? because both working same for me – ios coder Feb 11 '21 at 22:55
1

@swiftPunk `loadView` actually *creates* the view. If you don't override it, the [documentation](https://developer.apple.com/documentation/uikit/uiviewcontroller/1621454-loadview) says that a "plain UIView object" will be created instead. Although this is exactly what I did in with `view = UIView()`, you might need to change it to something else, like `view = UIImageView()`. Meanwhile `viewDidLoad` is called after the view is already created. That is mainly used when the view controller is loaded from the storyboard. See this [answer](https://stackoverflow.com/a/573968/14351818) – aheze Feb 11 '21 at 23:05
@aheze I'm doing the exact same thing as you, but I'm getting `Replace 'backgroundColor' with 'coder'` – Jalil Nov 05 '21 at 19:05
@Jalil I just double checked and works fine for me. Maybe [ask a new question](https://stackoverflow.com/questions/ask)? – aheze Nov 05 '21 at 19:10

score 2 · Answer 2 · answered Feb 11 '21 at 22:47

Try this

class UIViewControllerModel: UIViewController {

 var backgroundColor: UIColor 

 init(backgroundColor: UIColor) {
     self.backgroundColor = backgroundColor
     super.init(nibName: nil, bundle: nil)

 }

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

 override func loadView() {

  self.view.backgroundColor = backgroundColor

 }

}

How can I initialize a variable for UIViewController class in right syntax?

2 Answers2