import UIKit
class RightAnswerButtonClass: UIButton {
var rightAnswer: Bool
init() {
super.init()
rightAnswer = false
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
I am trying to create a custom class button with the variable "rightanswer" stored as a bool. However, when I try to build, I recieve the error "Must call a designated initializer"
It's compile time error where super class designated initialisation not implement.
As subclass of UIButton must implement(override) init(frame:CGRect)("Designated Initialiser for UIButton") like as below,
> override init(frame: CGRect) {
super.init(frame: frame)
rightAnswer = true
}
Related
I am kind of new to Swift and I can't figure this out. I have two classes where I need to use the same function to set up a custom UIStackVIew (Rating Control that shows rating stars). Each class has a variable called value that needs to be passed inside the function. I don't want to be duplicating the same code of the setUpStackView function inside each class. I have the following code:
class Class1: UIStackView {
var variable1 = "value1"
override init(frame: CGRect){
super.init(frame: frame)
}
required init?(coder aDecoder: NSCoder){
super.init(coder: aDecoder)
}
setUpStackView(value: variable1)
}
class Class2: UIStackView {
var variable2 = "value2"
override init(frame: CGRect){
super.init(frame: frame)
}
required init?(coder aDecoder: NSCoder){
super.init(coder: aDecoder)
}
setUpStackView(value: variable2)
}
extension Class1 {
func setUpStackView(value: String){
//code to set UIStackView rating control and to use the variable value
}
}
How can I implement the extension for the Class2? I am stuck with this. Any help would be greatly appreciated!
One solution can be moved common code to protocol where you can abstract out:
protocol BaseStackView {
var variable :String { get set }
}
class Class1: UIStackView,BaseStackView {
var variable = "value1"
override init(frame: CGRect){
super.init(frame: frame)
self.setUpStackView(value: variable)
}
required init(coder: NSCoder) {
super.init(coder: coder)
self.setUpStackView(value: variable)
}
}
class Class2: UIStackView,BaseStackView {
var variable = "value2"
override init(frame: CGRect){
super.init(frame: frame)
self.setUpStackView(value: variable)
}
required init(coder: NSCoder) {
super.init(coder: coder)
self.setUpStackView(value: variable)
}
}
extension UIStackView {
func setUpStackView(value: String) {
//Your setup here
}
}
You have many options.
You can make Class2 inherit from Class1:
class Class2: Class1 {
var value = "value2" //You have access to Class1's value, so you can change it here
setUpStackView(value: value) //But there's a problem here
}
But you can't just call a function when you're in the middle of a class declaration.
But you can do this in the initializer:
class Class2: Class1 {
override init(frame: CGRect) {
super.init(frame: frame)
value = "value2"
setUpStackView(value: value)
}
required init(coder aDecoder: NSCoder){
super.init(coder: aDecoder)
value = "value2"
setUpStackView(value: value)
}
}
The above is kind of jank because you're referencing class properties within its own initializer.
Here's another solution:
You can make your setup function a function extension of UIStackView:
extension UIStackView {
func setUpStackView(value: String) {
//Your setup here
self.someProperty = value //self is referring to the stackview itself
}
}
Another option is to create a static function.
extension Class1 {
static func setUpStackView(stackVw: UIStackView, value: String) {
stackVw.someProperty = value
//Doing it like this still makes this function "belong" to Class1
//It also makes it so anyone can set up their stack view like
//this because they have to pass their stack view in here
}
}
Usage would be like this regardless of what class you're in and what inheritance hierarchy you have:
override init(frame: CGRect) {
super.init(frame: frame)
Class1.setUpStackVw(stackVw: self, value: self.variable)
}
required init(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
Class1.setUpStackVw(stackVw: self, value: self.variable)
}
Yet another option is to create a protocol from which both Class1 and Class2 conform to.
protocol StackVwWithSpecialSetUp where Self: UIStackView {
var value: String {get}
}
extension StackVwWithSpecialSetUp {
func setUpStackView()
{
self.someProperty = self.value
}
}
And then you'd have your class conform to it
class Class1Or2: UIStackView, StackVwWithSpecialSetUp {
var value: String = "blah" //Compiler will force you to implement this
override init(frame: CGRect) {
super.init(frame: frame)
//Now you can use this
setUpStackVw()
}
required init(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
//You can use this here too
setUpStackVw()
}
}
Perhaps the way I'd do it is to just eliminate the need for the value property altogether:
class Class1: UIStackView {
override init(frame: CGRect) {
super.init(frame: frame)
setUpStackVw()
}
required init(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
setUpStackVw()
}
func setUpStackVw()
{
self.accessibilityHint = "value1"
}
}
//////////
class Class2: Class1 {
override func setUpStackVw()
{
self.someProperty = "value2"
}
}
I'm trying to write a class that is of type UIView, but on initialization I want it to take an extra parameter, but I can't figure out how to get around the UIView needing its params instead. Any help is much appreciated!
class MenuBar: UIView {
let homeController: HomeController
init(controller: HomeController){
homeController = controller
super.init()
}
override init(frame: CGRect) {
super.init(frame: frame)
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
In the ViewController I'm initializing it like this:
let menuBar: MenuBar = {
let mb = MenuBar(controller: self)
return mb
}()
Try this.
class MenuBar: UIView {
let homeController: HomeController
required init(controller: HomeController){
homeController = controller
super.init(frame: CGRect.zero)
// Can't call super.init() here because it's a convenience initializer not a desginated initializer
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
From my experience this is what works best if you want to have custom initialiser for UIView:
class CustomView : UIView {
private var customProperty: CustomClass
required init(customProperty: CustomClass) {
super.init(frame: .zero)
self.customProperty = customProperty
self.setup()
}
required override init(frame: CGRect) {
super.init(frame: frame)
setup()
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
self.setup()
}
fileprivate func setup() {
//Here all custom code for initialisation (common for all creation methods)
}
}
This approach allows you to keep common initialisation code regardless of method of creating the view (both storyboard and code)
That's about creating UIView properly.
Additionally I would recommend to avoid passing UIViewController to UIView - I think you are trying to solve some problem in a wrong way.
Much better ways to communicate between those two is to use delegate or closure - but that's a bit off-topic - maybe you can create another question about why you want to pass it like this.
I use this tutorial in order to create a simple Shopping List app. I have a problem with those lines of code:
override func viewDidLoad() {
super.viewDidLoad()
required init?(coder aDecoder: NSCoder) { // error appears here
self.init(coder: aDecoder);
loadItems()
}
}
There is an error: Initializers may only be declared within a type.
Why it is not correct? What should I change here?
Initializers must be placed at the type level, not inside any other functions.
class Item: NSObject, NSCoding {
required init?(coder aDecoder: NSCoder) {
self.init(coder: aDecoder)
loadItems()
}
override func viewDidLoad() {
super.viewDidLoad()
// this code runs when the view loads
}
func loadItems() {
// item loading code here
}
}
I'm trying to subclass UILabel and automatically generate a value for one of the properties, so that I can initialize with some values, and have others randomly generated.
For example, here I'd want to be able to create a new MyLabel, pass in a value for labelString and and have the value for labelNumber generated randomly.
class MyLabel: UILabel {
var labelString : String!
var labelNumber : Int!
init(frame: CGRect, labelString: String) {
self.labelString = labelString
self.labelNumber = createNumber()
super.init(frame: frame)
}
func createNumber() -> Int {
return Int(arc4random())
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
I get the error "Use of 'self' in method call before super.init initializes self." Is there a way to fix this, or a better pattern to be using?
Many thanks for any help!
You can't call instance methods from init until everything has been initialized. One way to handle it is to make createNumber a static function which doesn't require the class to be initialized to be called:
class MyLabel: UILabel {
var labelString : String!
var labelNumber : Int!
init(frame: CGRect, labelString: String) {
self.labelString = labelString
self.labelNumber = MyLabel.createNumber()
super.init(frame: frame)
}
static func createNumber() -> Int {
return Int(arc4random())
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
Another way to handle it is to move the initialization of labelNumber after the call to super.init. This works because labelNumber is an Optional and thus is initially given the value of nil which meets the requirement that all properties of the subclass MyLabel are initialized before calling the init of the superclass.
class MyLabel: UILabel {
var labelString : String!
var labelNumber : Int!
init(frame: CGRect, labelString: String) {
self.labelString = labelString
super.init(frame: frame)
self.labelNumber = createNumber()
}
func createNumber() -> Int {
return Int(arc4random())
}
required init?(coder aDecoder: NSCoder) {
fatalError("init(coder:) has not been implemented")
}
}
I have a custom UITextField and I'm trying to declare it like:
let textField = StandardTextField() // pretty much like UITextField()
My custom text field looks like:
class StandardTextField: UITextField {
init(frame: CGRect, size: CGFloat) {
super.init(frame: frame)
// some initialization
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
}
This is giving me an error because TextField has no initializer with no arguments. I tried adding:
init() {
super.init()
}
But this isn't possible since super.init() isn't the designated initializer. How can I achieve this?
You are probably looking for a convenience initialiser. But you will need to define a default frame size for your UITextField. Try like this:
class StandardTextField: UITextField {
convenience init() {
self.init(frame: CGRect(x: 0, y: 0, width: 200, height: 50))
// some initialisation for init with no arguments
}
override init(frame: CGRect) {
super.init(frame: frame)
// some initialisation for init with frame
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
}
Well unless I'm blatantly missing something, you've declared your class as class Textfield: UITextField and based on how you're trying to create your object, your class should be defined as class StandardField: UITextField and the class doesn't need any initializers as Leo said.
class StandardTextField: UITextField {
//no initializers
}