I needed to delegate an click action for my UIView class to my UIViewController class since swift does not support multiple class inheritance. So i wanted it such that once a button is clicked on my subview, a function in my ViewController class is called. Am using protocol delegate to achieve this but on the click of my button it does not work for me as the function does not get called. Please help me out. Code snippet would be largely appreciated.
ViewController
var categoryItem: CategoryItem! = CategoryItem() //Category Item
private func setupExplore() {
//assign delegate of category item to controller
self.categoryItem.delegate = self
}
//function to be called
extension BrowseViewController: ExploreDelegate {
func categoryClicked(category: ProductCategory) {
print("clicked")
let categoryView = ProductByCategoryView()
categoryView.category = category
categoryView.modalPresentationStyle = .overCurrentContext
self.navigationController?.pushViewController(categoryView, animated: true)
}
}
Explore.swift (subview)
import UIKit
protocol ExploreDelegate:UIViewController {
func categoryClicked(category: ProductCategory)
}
class Explore: UIView {
var delegate: ExploreDelegate?
class CategoryItem: UIView {
var delegate: ExploreDelegate?
var category: ProductCategory? {
didSet {
self.configure()
}
}
var tapped: ((_ category: ProductCategory?) -> Void)?
func configure() {
self.layer.cornerRadius = 6
self.addGestureRecognizer(UITapGestureRecognizer(target: self, action: #selector(self.categoryTapped)))
self.layoutIfNeeded()
}
#objc func categoryTapped(_ sender: UIGestureRecognizer) {
delegate?.categoryClicked(category: ProductCategory.everything)
self.tapped?(self.category)
}
}
I have a viewController with another containerView insider set up to appear temporarily (added programmatically). The containerView is a sort of operation bar, which allows you to change values of the viewController. The protocol called from an IBAction of a button however, does not call the protocol set up inside the viewController class.
Here is the code from both classes:
class viewController: UIViewController, updateListDelegate {
let dataSource = containerView()
override func viewDidLoad() {
super.viewDidLoad()
dataSource.delegate = self
}
func updateList(sender: containerView) {
print("is called") //is not printed
}
}
The code from the containerView:
protocol updateListDelegate {
func updateList(containerView)
}
class containerView: UIViewController {
var delegate: updateListDelegate?
#IBAction func AddSong(_ sender: UIButton) {
self.delegate?.updateList(sender: self)
}
}
If this method is only to be called from one object, then, in my opinion, I would not define a protocol. If multiple objects are to call this method, then I would define a protocol. This is typically how you would call a method backwards, using a basic delegate.
class ViewController: UIViewController {
let container = ContainerView()
override func viewDidLoad() {
super.viewDidLoad()
container.viewControllerDelegate = self
// push to this instance of container at some point
}
func doSomething() {
print("great success")
}
}
class ContainerView: UIViewController {
weak var viewControllerDelegate: ViewController?
#objc func someAction() {
if let viewControllerDelegate = viewControllerDelegate {
viewControllerDelegate.doSomething()
}
}
}
// prints "great success" when someAction() called
One of the most common mistakes people make is not keeping track of instances. For delegates to work, you must be sure you are using the specific instances that you've instantiated and assigned those delegates to.
I am using BMPlayer library and want to implement custom control, for which I have the following class which confirm to following protocol
#objc public protocol BMPlayerControlViewDelegate: class {
func controlView(controlView: BMPlayerControlView, didChooseDefition index: Int)
func controlView(controlView: BMPlayerControlView, didPressButton button: UIButton)
func controlView(controlView: BMPlayerControlView, slider: UISlider, onSliderEvent event: UIControlEvents)
#objc optional func controlView(controlView: BMPlayerControlView, didChangeVideoPlaybackRate rate: Float)
}
open class BMPlayerControlView: UIView {
open weak var delegate: BMPlayerControlViewDelegate?
open weak var player: BMPlayer?
// Removed rest of the code for clarity
open func onButtonPressed(_ button: UIButton) {
autoFadeOutControlViewWithAnimation()
if let type = ButtonType(rawValue: button.tag) {
switch type {
case .play, .replay:
if playerLastState == .playedToTheEnd {
hidePlayToTheEndView()
}
default:
break
}
}
delegate?.controlView(controlView: self, didPressButton: button)
}
}
I am extending BMPlayerControlView class to extend the control view using the following code.
class BMPlayerCustomControlStyle3: BMPlayerControlView {
}
class BMPlayerStyle3: BMPlayer {
class override func storyBoardCustomControl() -> BMPlayerControlView? {
return BMPlayerCustomControlStyle3()
}
}
My question is, how do I invoke didPressButton delegate method? I don't want to overwrite onButtonPressed, I tried the following
extension BMPlayerCustomControlStyle3:BMPlayerControlViewDelegate {
func controlView(controlView: BMPlayerControlView, didChooseDefition index: Int) {
}
func controlView(controlView: BMPlayerControlView, didPressButton button: UIButton) {
print("Did Press Button Invoked")
}
func controlView(controlView: BMPlayerControlView, slider: UISlider, onSliderEvent event: UIControlEvents) {
}
}
And this doesn't seem to work, what am I missing here?
Thanks.
If you want your BMPlayerControlView subclass to also act as the delegate object, you need to set the delegate property as well (and conform to the BMPlayerControlViewDelegate protocol as you are already doing).
One way to do so is by overriding the delegate superclass property in your subclass:
class BMPlayerCustomControlStyle3: BMPlayerControlView {
override open weak var delegate: BMPlayerControlViewDelegate? {
get { return self }
set { /* fatalError("Delegate for internal use only!") */ }
}
}
Of course, when using the delegate internally such as this, you won't allow it to be used by BMPlayerControlView clients at all. The overridden set above ensures you get an error if trying to do so.
I am creating a UIView programmatically in static method and want to add UITapGestureRecognizer which will call another static method in my Helper class.
Helper.swift :
static func showLoadingPopUp(frame: CGRect) -> UIView {
let transView = UIView.init(frame: frame!)
let tapGesture = UITapGestureRecognizer(target: self, action: "transViewTapped:")
transView.addGestureRecognizer(tapGesture)
return transView
}
static func transViewTapped(gesture: UITapGestureRecognizer) {
print("Oh Tapped!!!")
}
But it ends up with the following message probably because of the static nature of my method. Also Helper.swift is simple swift class (not UIView or UIViewController)
Error:
Unrecognized selector +[JaClassified.Helper transViewTapped:]
If your class is not a descendant of NSObject, you may need to bridge the static func to Objective-C (since old style Objective-C selector works on NSObjects).
So, in your case, you could either declare you Helper class as
class Helper: NSObject {
...
}
or, you can bridge your transViewTapped: to Objective-C by prefix it with an #objc
#objc static func transViewTapped(gesture: UITapGestureRecognizer) {
...
}
Hope it helps.
I've got a protocol extension it used to work perfectly before swift 2.2.
Now I have a warning that tells me to use the new #selector, but if I add it
no method declared with Objective-C Selector.
I tried to reproduce the issue in this few lines of code, that can be easily copy and paste also into playground
protocol Tappable {
func addTapGestureRecognizer()
func tapGestureDetected(gesture:UITapGestureRecognizer)
}
extension Tappable where Self: UIView {
func addTapGestureRecognizer() {
let gesture = UITapGestureRecognizer(target: self, action:#selector(Tappable.tapGestureDetected(_:)))
addGestureRecognizer(gesture)
}
}
class TapView: UIView, Tappable {
func tapGestureDetected(gesture:UITapGestureRecognizer) {
print("Tapped")
}
}
There is also a suggestion to append to that method in the protocol #objc, but if I do it asks me also to add it to the class that implements it, but once I add the class doesn't conform to the protocol anymore, because it doesn't seems to see the implementation in the protocol extension.
How can I implement this correctly?
I had a similar problem. here is what I did.
Marked the protocol as #objc.
Marked any methods I extended with a default behavior as optional.
Then used Self. in the #selector.
#objc public protocol UpdatableUserInterfaceType {
optional func startUpdateUITimer()
optional var updateInterval: NSTimeInterval { get }
func updateUI(notif: NSTimer)
}
public extension UpdatableUserInterfaceType where Self: ViewController {
var updateUITimer: NSTimer {
return NSTimer.scheduledTimerWithTimeInterval(updateInterval, target: self, selector: #selector(Self.updateUI(_:)), userInfo: nil, repeats: true)
}
func startUpdateUITimer() {
print(updateUITimer)
}
var updateInterval: NSTimeInterval {
return 60.0
}
}
You can create a property which is a Selector... Example:
protocol Tappable {
var selector: Selector { get }
func addTapGestureRecognizer()
}
extension Tappable where Self: UIView {
func addTapGestureRecognizer() {
let gesture = UITapGestureRecognizer(target: self, action: selector)
addGestureRecognizer(gesture)
}
}
class TapView: UIView, Tappable {
var selector = #selector(TapView.tapGestureDetected(_:))
func tapGestureDetected(gesture:UITapGestureRecognizer) {
print("Tapped")
}
}
The error stops to show and it is not more necessary to set your protocol and class with the #objc decorator.
This solution is not the most elegant, but looks ok until now.
This answer is quite similar to Bruno Hecktheuers, but instead of having everyone that wants to conform to the "Tappable" protocol implement the variable "selector", we choose to pass it as a parameter to the addTapGestureRecognizer function:
protocol Tappable {
func addTapGestureRecognizer(selector selector: Selector)
func tapGestureDetected(gesture:UITapGestureRecognizer)
}
extension Tappable where Self: UIView {
func addTapGestureRecognizer(selector selector: Selector)
let gesture = UITapGestureRecognizer(target: self, action: selector)
addGestureRecognizer(gesture)
}
}
class TapView: UIView, Tappable {
func tapGestureDetected(gesture:UITapGestureRecognizer) {
print("Tapped")
}
}
and then just pass the selector wherever it is used:
addTapGestureRecognizer(selector: #selector(self.tapGestureDetected(_:)))
This way we avoid having the ones implementing this protocol having to implement the selector variable and we also avoid having to mark everyone using this protocol with "#objc". Feels like this approach is less bloated.
Here is a working example using Swift 3. It uses a standard Swift protocol without the need for any #objc decorations and a private extension to define the callback function.
protocol PlayButtonPlayable {
// be sure to call addPlayButtonRecognizer from viewDidLoad or later in the display cycle
func addPlayButtonRecognizer()
func handlePlayButton(_ sender: UITapGestureRecognizer)
}
fileprivate extension UIViewController {
#objc func _handlePlayButton(_ sender: UITapGestureRecognizer) {
if let playable = self as? PlayButtonPlayable {
playable.handlePlayButton(sender)
}
}
}
fileprivate extension Selector {
static let playTapped =
#selector(UIViewController._handlePlayButton(_:))
}
extension PlayButtonPlayable where Self: UIViewController {
func addPlayButtonRecognizer() {
let playButtonRecognizer = UITapGestureRecognizer(target: self, action: .playTapped)
playButtonRecognizer.allowedPressTypes = [ NSNumber(value: UIPressType.playPause.rawValue as Int) ]
view.addGestureRecognizer(playButtonRecognizer)
}
}
I happened to see this in the side bar, I recently had this same issue.. Unfortunately, due to Objective-C runtime limitations you cannot use #objc on protocol extensions, I believe this issue was closed early this year.
The issue arises because the extension is added after the conformance of the protocol, therefor there is no way to guarantee that conformance to the protocol is met. That said, it is possible to call a method as a selector from anything that subclasses NSObject and conforms to the protocol. This is most often done with delegation.
This implies you could create an empty wrapper subclass that conforms to the protocol and use the wrapper to call its methods from the protocol that are defined in the wrapper, any other undefined methods from the protocol can be passed to the delegate. There are other similar solutions that use a private extension of a concrete class such as UIViewController and define a method that calls the protocol method but these are also tied to a particular class and not a default implementation of a particular class that happens to conform to the protocol.
Realize that you are trying to implement a default implementation of a protocol function that uses another of it's own protocol functions to define a value for it's own implementation. whew!
Protocol:
public protocol CustomViewDelegate {
func update()
func nonDelegatedMethod()
}
View:
Use a delegate, and define a wrapper method to safely unwrap the delegate’s method.
class CustomView: UIView {
let updateButton: UIButton = {
let button = UIButton(frame: CGRect(origin: CGPoint(x: 50, y: 50), size: CGSize(width: 150, height: 50)))
button.backgroundColor = UIColor.lightGray
button.addTarget(self, action: #selector(doDelegateMethod), for: .touchUpInside)
return button
}()
var delegate:CustomViewDelegate?
required init?(coder aDecoder: NSCoder) {
fatalError("Pew pew, Aghh!")
}
override init(frame: CGRect) {
super.init(frame: frame)
addSubview(updateButton)
}
#objc func doDelegateMethod() {
if delegate != nil {
delegate!.update()
} else {
print("Gottfried: I wanted to be a brain surgeon, but I had a bad habit of dropping things")
}
}
}
ViewController:
Conform the View Controller to the view’s delegate: and implement the protocol’s method.
class ViewController: UIViewController, CustomViewDelegate {
let customView = CustomView(frame: CGRect(origin: CGPoint(x: 100, y: 100), size: CGSize(width: 200, height: 200)))
override func viewDidLoad() {
super.viewDidLoad()
customView.backgroundColor = UIColor.red
customView.delegate = self //if delegate is not set, the app will not crash
self.view.addSubview(customView)
}
// Protocol -> UIView Button Action -> View Controller's Method
func update() {
print("Delegating work from View that Conforms to CustomViewDelegate to View Controller")
}
//Protocol > View Controller's Required Implementation
func nonDelegatedMethod() {
//Do something else
}
}
Note that the view controller only had to conform to the delegate and did not set the selector of some property of the view, this separates the view (and it's protocol) from view controller.
You already have a UIView named TapView that inherits from UIView and Tappable so your implementation could be:
Protocol:
protocol TappableViewDelegate {
func tapGestureDetected(gesture:UITapGestureRecognizer)
}
TappableView:
class TappableView: UIView {
var delegate:TappableViewDelegate?
required init?(coder aDecoder: NSCoder) {
fatalError("Pew pew, Aghh!")
}
override init(frame: CGRect) {
super.init(frame: frame)
let gesture = UITapGestureRecognizer(target: self, action: #selector(doDelegateMethod(gesture:)))
addGestureRecognizer(gesture)
}
#objc func doDelegateMethod(gesture:UITapGestureRecognizer) {
if delegate != nil {
delegate!.tapGestureDetected(gesture: gesture)
} else {
print("Gottfried: I wanted to be a brain surgeon, but I had a bad habit of dropping things")
}
}
}
ViewController:
class ViewController: UIViewController, TappableViewDelegate {
let tapView = TappableView(frame: CGRect(origin: CGPoint(x: 100, y: 100), size: CGSize(width: 200, height: 200)))
override func viewDidLoad() {
super.viewDidLoad()
tapView.backgroundColor = UIColor.red
tapView.delegate = self
self.view.addSubview(tapView)
}
func tapGestureDetected(gesture: UITapGestureRecognizer) {
print("User did tap")
}
}