How can I init a UIButton subclass?

Question

I tried to add a double value to a subclass of UIButton in Swift. I tried all kind of inits and get and set options, but I couldn’t get it to work.

So I started with this:

class CVSTButton : UIButton {
    var cvstPosition: Double

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

        super.init(coder: aDecoder)
    }
}

Then I tried:

class CVSTButton : UIButton {
    var cvstPosition: Double {
        get {
            return self.cvstPosition
        }
        set {
            self.cvstPosition = newValue
        }

    }

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

What’s is wrong here?

Imanou Petit · Answer 1 · 2017-04-17T09:14:06.673

With Swift 3, according to your needs, you may choose one of the seven following code snippets to solve your problem.

1. Create your `UIButton` subclass with a custom initializer

This solution allows you to create instances of your UIButton subclass with the appropriate value for your property. With this solution, you can only create instances of your UIButton subclass programmatically.

import UIKit

class CustomButton: UIButton {

    var myValue: Int

    required init(value: Int = 0) {
        // set myValue before super.init is called
        self.myValue = value

        super.init(frame: .zero)

        // set other operations after super.init, if required
        backgroundColor = .red
    }

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

}

Usage:

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let button = CustomButton(value: 0)
        // let button = CustomButton() // also works
        button.setTitle("Hello", for: .normal)

        // auto layout
        button.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(button)
        button.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        button.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

        print(button.myValue) // prints 0
    }

}

2. Create your `UIButton` subclass with a convenience initializer

This solution allows you to create instances of your UIButton subclass with the appropriate value for your property. With this solution, you can only create instances of your UIButton subclass programmatically.

import UIKit

class CustomButton: UIButton {

    var myValue: Int

    convenience init(squareOf value: Int) {
        self.init(value: value * value)
    }

    required init(value: Int = 0) {
        // set myValue before super.init is called
        self.myValue = value

        super.init(frame: .zero)

        // set other operations after super.init, if required
        backgroundColor = .red
    }

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

}

Usage:

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let button = CustomButton(squareOf: 10)
        // let button = CustomButton(value: 100) // also works
        button.setTitle("Hello", for: .normal)

        // auto layout
        button.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(button)
        button.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        button.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

        print(button.myValue) // prints 100
    }

}

3. Create your `UIButton` subclass with `init(frame: CGRect)` initializer

With this solution, you can only create instances of your UIButton subclass programmatically.

import UIKit

class CustomButton: UIButton {

    var myValue: Int

    override init(frame: CGRect) {
        // set myValue before super.init is called
        self.myValue = 0

        super.init(frame: frame)

        // set other operations after super.init, if required
        backgroundColor = .red
    }

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

}

Usage:

import UIKit

class ViewController: UIViewController {

    override func viewDidLoad() {
        super.viewDidLoad()

        let button = CustomButton(frame: .zero)
        //let button = CustomButton() // also works
        button.setTitle("Hello", for: .normal)

        // auto layout
        button.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(button)
        button.centerXAnchor.constraint(equalTo: view.centerXAnchor).isActive = true
        button.centerYAnchor.constraint(equalTo: view.centerYAnchor).isActive = true

        print(button.myValue) // prints 0
    }

}

4. Create your `UIButton` subclass with `init?(coder aDecoder: NSCoder)` initializer

With this solution, you can create instances of your UIButton subclass from Storyboard.

import UIKit

class CustomButton: UIButton {

    var myValue: Int

    required init?(coder aDecoder: NSCoder) {
        // set myValue before super.init is called
        self.myValue = 0

        super.init(coder: aDecoder)

        // set other operations after super.init, if required
        backgroundColor = .red
    }

}

Usage:

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var button: CustomButton!

    override func viewDidLoad() {
        super.viewDidLoad()

        print(button.myValue) // prints 0
    }

}

5. Create your `UIButton` subclass with `init(frame: CGRect)` and `init?(coder aDecoder: NSCoder)` initializers

With this solution, you can create instances of your UIButton subclass programmatically or from Storyboard.

import UIKit

class CustomButton: UIButton {

    var myValue: Int

    override init(frame: CGRect) {
        // set myValue before super.init is called
        self.myValue = 0

        super.init(frame: frame)

        // set other operations after super.init, if required
        backgroundColor = .red
    }

    required init?(coder aDecoder: NSCoder) {
        // set myValue before super.init is called
        self.myValue = 0

        super.init(coder: aDecoder)

        // set other operations after super.init if required
        backgroundColor = .red
    }

}

6. Create your `UIButton` subclass with a default property value for your property

As an alternative to the previous solutions, you can assign an initial value to your property outside of the initializers.

import UIKit

class CustomButton: UIButton {

    var myValue: Int = 0

    override init(frame: CGRect) {
        super.init(frame: frame)

        // set other operations after super.init, if required
        backgroundColor = .red
    }

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

        // set other operations after super.init if required
        backgroundColor = .red
    }

}

7. Create your `UIButton` subclass with your property having an optional type

If you don't want to / can't set a default value to your property when your button is created, you must set your property type as an optional.

import UIKit

class CustomButton: UIButton {

    var myValue: Int? = nil

    override init(frame: CGRect) {
        super.init(frame: frame)

        // set other operations after super.init, if required
        backgroundColor = .red
    }

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

        // set other operations after super.init if required
        backgroundColor = .red
    }

}

I like that you gave scenarios of why to use each code snippet. Phenomenal response - wish more questions were answered like this. — Sami, Jan 06 '17 at 03:02
In the usage part of snippet 3, where a frame is used as the initialiser, it would be clearer to use something like `CustomButton(frame: CGRect(x: 100, y: 300, width: 200, height: 50))` rather than `CustomButton(frame: .zero)` and auto layout — paulo62, Mar 19 '20 at 17:45

score 12 · Answer 2 · edited Jan 14 '22 at 18:52

12

You need two things there -- (1) cvstPosition needs an initial value, either in the declaration or in the init before you call super.init(). (2) That call to fatalError is put in so you don't forget to implement the initializer -- it’s basically an on-purpose crash. Delete!

Setting the initial value in the declaration, there isn’t any need for an init:

class CVSTButton : UIButton {
    var cvstPosition: Double = 0
}

Or setting the initial value in the initializer:

class CVSTButton : UIButton {
    var cvstPosition: Double

    required init(coder aDecoder: NSCoder) {
        cvstPosition = 0

        super.init(coder: aDecoder)
    }
}

edited Jan 14 '22 at 18:52

Peter Mortensen

30,738
21
105
131

answered Nov 22 '14 at 16:40

Nate Cook

92,417
32
217
178

Ah great so i just have to declare and give the variable a init value! – Alexander Schutte Nov 22 '14 at 20:57
You need a question mark after `init` in Swift 2.2, so `required init?(coder aDecoder: NSCoder) {` – Dan Rosenstark Apr 07 '16 at 23:39

dimpiax · Answer 3 · 2022-01-16T22:21:27.767

8

Swift >= 2.2:

Since this version subclassing the UIButton, makes your button to have .custom type.

Swift 2:

convenience init(type buttonType: UIButtonType) {
    super.init(frame: CGRectZero)

    // this button be automatically .Custom
}

Swift:

override class func buttonWithType(buttonType: UIButtonType) -> AnyObject {
    let button = super.buttonWithType(buttonType) as! UIButton
    // your default code
    return button
}

edited Jan 16 '22 at 22:21

answered Aug 19 '15 at 00:17

dimpiax

12,093
5
62
45

You want to insert 'public' in there. I.e.: override public class func – u2Fan Aug 24 '15 at 22:16
Not, of course. Read that public is the scope between projects. – dimpiax Aug 24 '15 at 23:20
Re *"...your subclass becomes with type .Custom default."*: That is close to incomprehensible. Can you [fix](https://stackoverflow.com/posts/32084565/edit) it? (But ***without*** "Edit:", "Update:", or similar - the answer should appear as if it was written today.) – Peter Mortensen Jan 14 '22 at 18:54

score 4 · Answer 4 · edited Jan 14 '22 at 18:57

Note: I'm using Swift 3 in Xcode 8.3.3

This is a simple and easy workaround I've been using when needing to add custom properties and methods to a UIButton:

class CVSTButton: UIButton {

    var cvstPosition: Double

    static func button(withCVSTPosition cvstPosition: Double) -> CVSTButton {

        let button = CVSTButton(type: .detailDisclosure) // You may adjust the initializer used to suit your needs.

        button.cvstPosition = cvstPosition // Then you can simply set the the properties (which are passed as arguments to the factor/class method)

        return button

    }

}

To use it:

let cvstButton = CVSTButton.button(withCVSTPosition: 2.0)

How can I init a UIButton subclass?

4 Answers4

1. Create your `UIButton` subclass with a custom initializer

2. Create your `UIButton` subclass with a convenience initializer

3. Create your `UIButton` subclass with `init(frame: CGRect)` initializer

4. Create your `UIButton` subclass with `init?(coder aDecoder: NSCoder)` initializer

5. Create your `UIButton` subclass with `init(frame: CGRect)` and `init?(coder aDecoder: NSCoder)` initializers

6. Create your `UIButton` subclass with a default property value for your property

7. Create your `UIButton` subclass with your property having an optional type

Swift >= 2.2:

Swift 2:

Swift:

Linked

Related

How can I init a UIButton subclass?

4 Answers4

1. Create your UIButton subclass with a custom initializer

2. Create your UIButton subclass with a convenience initializer

3. Create your UIButton subclass with init(frame: CGRect) initializer

4. Create your UIButton subclass with init?(coder aDecoder: NSCoder) initializer

5. Create your UIButton subclass with init(frame: CGRect) and init?(coder aDecoder: NSCoder) initializers

6. Create your UIButton subclass with a default property value for your property

7. Create your UIButton subclass with your property having an optional type

Swift >= 2.2:

Swift 2:

Swift:

Linked

Related

1. Create your `UIButton` subclass with a custom initializer

2. Create your `UIButton` subclass with a convenience initializer

3. Create your `UIButton` subclass with `init(frame: CGRect)` initializer

4. Create your `UIButton` subclass with `init?(coder aDecoder: NSCoder)` initializer

5. Create your `UIButton` subclass with `init(frame: CGRect)` and `init?(coder aDecoder: NSCoder)` initializers

6. Create your `UIButton` subclass with a default property value for your property

7. Create your `UIButton` subclass with your property having an optional type