how to init a UIButton subclass?

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 UIKitclass 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 UIKitclass 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 UIKitclass 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 UIKitclass 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 UIKitclass 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 UIKitclass 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 UIKitclass 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 UIKitclass 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 UIKitclass 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 UIKitclass 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 UIKitclass 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    }}

Two things you need there -- (1) cvstPosition need 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 initial value in the declaration, no 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)    }}

Swift >= 2.2:

Just inherit from UIButton, and your subclass becomes with type .Custom default.

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}