How can I programmatically add a uiswitch and call an action when on and one when off? Ive been searching for hours now. Can I please have some help? I know how to add the switch but it stays on the screen no matter what scene I'm on. So far, I've been able to add the button and make it switch from on to off, but for some reason the switch just says on the screen in every scene. I was lost after that so I followed this; from How to programmatically put a UISwitch in a SpriteKit/Skcene
Yes it is possible. Just use this code in your SKScene class:
override func didMoveToView(view: SKView) {
/* Setup your scene here */
let switchDemo = UISwitch(frame:CGRectMake(150, 300, 0, 0))
switchDemo.on = true
switchDemo.setOn(true, animated: false)
switchDemo.addTarget(self, action: "switchValueDidChange:", forControlEvents: .ValueChanged)
self.view!.addSubview(switchDemo)
}
Helper method:
func switchValueDidChange(sender:UISwitch!)
{
if (sender.on == true){
print("on")
}
else{
print("off")
}
}
I kept getting errors so I did what Xcode suggested which ended up with the SIGBART error.
You are calling the selector wrong on the addTarget action line. They finally changed it at one point in Swift 2 to get rid of using strings for selector method calls, which now makes them a lot less error prone.
Change it to this (Swift 3 syntax)
switchDemo.addTarget(self, action: #selector(switchValueDidChange(_:)), for: .valueChanged)
You basically call #selector in the action parameter and include the method you want to call, in your case switchValueDidChange. Note the (_:) syntax at the end, thats indicating that the method you want to call takes a parameter, in your case a UISwitch.
func switchValueDidChange(_ sender: UISwitch) {
...
}
If you want to call a regular method that takes no parameters e.g
func switchValueDidChange() {
}
than you would just say
switchDemo.addTarget(self, action: #selector(switchValueDidChange), for: .valueChanged)
without the (_:) syntax.
Hope this helps
Updated to swift 5
override func didMoveToView(view: SKView) {
/* Setup your scene here */
let switchDemo = UISwitch(frame:CGRect(x: 150, y: 300, width: 0, height: 0))
switchDemo.isOn = true
switchDemo.setOn(true, animated: false)
switchDemo.addTarget(self, action: #selector(switchValueDidChange(_:)), for: .valueChanged)
self.view!.addSubview(switchDemo)
}
Helper method:
#objc func switchValueDidChange(_ sender: UISwitch!) {
if (sender.isOn){
print("on")
}
else{
print("off")
}
}
With parameter:
#IBOutlet var categorySwitch:UISwitch!
var categorySwitchIsOn:Bool = false
On viewDidLoad:
override func viewDidLoad() {
super.viewDidLoad()
categorySwitch.addTarget(self, action:#selector(ViewController.categorySwitchValueChanged(_:)), for: .valueChanged)
}
Associated function:
func categorySwitchValueChanged(_ sender : UISwitch!){
if sender.isOn {
categorySwitchIsOn = true
} else {
categorySwitchIsOn = false
}
}
Related
I am trying to implement a custom appearing/disappearing animation for a modal UIViewController in my app.
I have published the code showing this error here.
Here is the content related:
/// The view controller from which I'm trying to display the modal
class ViewController: UIViewController {
#IBAction func tapped() {
/// The modal showing
ModalTestViewController.show()
}
//...
}
/// The displayed modal
open class ModalTestViewController: TransitioningModalViewController {
init() {
super.init(nibName: "ModalTestViewController", bundle: .main)
transitioningDelegate = self
// 1. when I put transitioningDelegate here, case 1
}
public required init?(coder: NSCoder) {
fatalError()
}
open override func viewDidLoad() {
super.viewDidLoad()
// 2. if I put transitioningDelegate here, case 2
}
#IBAction func tapped() {
// a tap on the overlayView of my modal
dismiss(animated: true)
}
static func show() {
let modal = ModalTestViewController()
modal.modalPresentationStyle = .overCurrentContext
DispatchQueue.main.async {
UIApplication.shared.delegate?.window??.rootViewController?.present(modal, animated: true)
}
}
}
/// The default modal view controller, which all modals in my app should inherit
open class TransitioningModalViewController: UIViewController {
// MARK: View Properties
#IBOutlet weak var overlayView: UIView!
}
extension TransitioningModalViewController: UIViewControllerTransitioningDelegate {
public func animationController(
forPresented presented: UIViewController,
presenting: UIViewController,
source: UIViewController
) -> UIViewControllerAnimatedTransitioning? {
return TransitioningModalViewControllerPresenter()
}
public func animationController(
forDismissed dismissed: UIViewController
) -> UIViewControllerAnimatedTransitioning? {
return TransitioningModalViewControllerDismisser()
}
}
private final class TransitioningModalViewControllerPresenter: NSObject, UIViewControllerAnimatedTransitioning {
func transitionDuration(
using transitionContext: UIViewControllerContextTransitioning?
) -> TimeInterval {
return 0.5
}
func animateTransition(
using transitionContext: UIViewControllerContextTransitioning
) {
let toViewController: TransitioningModalViewController = transitionContext.viewController(
forKey: UITransitionContextViewControllerKey.to
) as! TransitioningModalViewController
let duration = transitionDuration(using: transitionContext)
toViewController.overlayView.alpha = 0.0
UIView.animate(
withDuration: duration
) {
toViewController.overlayView.alpha = 0.65
} completion: { result in
transitionContext.completeTransition(result)
}
}
}
private final class TransitioningModalViewControllerDismisser: NSObject, UIViewControllerAnimatedTransitioning {
func transitionDuration(
using transitionContext: UIViewControllerContextTransitioning?
) -> TimeInterval {
return 0.5
}
func animateTransition(
using transitionContext: UIViewControllerContextTransitioning
) {
let fromViewController: TransitioningModalViewController = transitionContext.viewController(
forKey: UITransitionContextViewControllerKey.from
) as! TransitioningModalViewController
let duration = transitionDuration(using: transitionContext)
UIView.animate(
withDuration: duration
) {
fromViewController.overlayView.alpha = 0.0
} completion: { result in
transitionContext.completeTransition(result)
}
}
}
The idea behind this is that the modal appearance should not be the usual bottom-to-top animation, but instead the overlay view should go from hidden to an alpha of 0,65.
Case 1: when I put transitioningDelegate = self in init(), the animation is killed and nothing happens.
Case 2: when I put it into the viewDidLoad(), the appearing animation is the default bottom-to-top one, but the disappearing one is the expecting one (with the overlay view vanishing).
It looks like something is wrong with the initial transitioningDelegate setting but I can't find what.
Thank you for your help!
In your original code, you are setting the delegate here:
open override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(animated)
transitioningDelegate = self
}
However, .present(...) is called before viewDidAppear(...), so the controller is presented with default slide-up animation.
Setting the delegate in init() doesn't work, because we have override the default presentation process... and the presented controller's view is never added to the view hierarchy.
This "quick fix" should do the job...
First, in ModalTestViewController, move setting the delegate to init():
init() {
super.init(nibName: "ModalTestViewController", bundle: .main)
transitioningDelegate = self
}
then, in TransitioningModalViewControllerPresenter, add these lines before the animation:
func animateTransition(
using transitionContext: UIViewControllerContextTransitioning
) {
let toViewController: TransitioningModalViewController = transitionContext.viewController(
forKey: UITransitionContextViewControllerKey.to
) as! TransitioningModalViewController
// add these lines \/
// get the "from" view controller
let fromVC = transitionContext.viewController(forKey: .from)!
// get the "to" view controller's view
let toView = transitionContext.view(forKey: .to)!
// set the frame of the "to" view to the initialFrame (the current frame) of the "from" VC
toView.frame = transitionContext.initialFrame(for: fromVC)
// get the transition container view
let container = transitionContext.containerView
// add the "to" view to the view hierarchy
container.addSubview(toView)
// add these lines /\
let duration = transitionDuration(using: transitionContext)
toViewController.overlayView.alpha = 0.0
UIView.animate(
withDuration: duration
) {
toViewController.overlayView.alpha = 0.65
} completion: { result in
transitionContext.completeTransition(result)
}
}
Personally, to make this more flexible, I would get rid of your overlayView and set the alpha on the controller's view itself.
I am creating a game and i keep getting this error for my bullet spawn method linked with a joystick. I want to repetitively spawn the bullet node while the joystick is active. Here is how i am creating a firing method
class GameScene: SKScene, SKPhysicsContactDelegate {
let bullet1 = SKSpriteNode(imageNamed: "bullet.png")
override func didMoveToView(view: SKView) {
if fireWeapon == true {
NSTimer.scheduledTimerWithTimeInterval(0.25, target: self,
selector: Selector ("spawnBullet1"), userInfo: nil, repeats: true)
}
}
func spawnBullet1(){
self.addChild(bullet1)
bullet1.position = CGPoint (x: hero.position.x , y:hero.position.y)
bullet1.xScale = 0.5
bullet1.yScale = 0.5
bullet1.physicsBody = SKPhysicsBody(rectangleOfSize: bullet1.size)
bullet1.physicsBody?.categoryBitMask = PhysicsCategory.bullet1
bullet1.physicsBody?.contactTestBitMask = PhysicsCategory.enemy1
bullet1.physicsBody?.affectedByGravity = false
bullet1.physicsBody?.dynamic = false
}
override func touchesBegan(touches: Set<UITouch>, withEvent
event:UIEvent?) {
for touch in touches {
let location = touch.locationInNode(self)
let node = nodeAtPoint(location)
if (CGRectContainsPoint(joystick.frame, location)) {
stickActive = true
if stickActive == true {
fireWeapon = true
}
}
override func touchesEnded(touches: Set<UITouch>, withEvent event:
UIEvent?) {
fireWeapon = false
}
the first bullet launches as planned and works great however, every time the second bullet launches the app crashes and i get this error "Attemped to add a SKNode which already has a parent". can someone tell me an alternative method
Your problem is exactly as the error says, you need to first remove the bullet from its parent before adding it again, or Make bullet1 a local property inside the spawnBullet function, so that each time you call the function a new bullet gets created and added as child to the scene instead of trying to re-add the same one.
I trying to change Cancel button color in UISearchBar implemented with UISearchController (iOS 8 and greater). This is a code I use:
if self.resultSearchController.active {
for subView in self.resultSearchController.searchBar.subviews {
for subsubView in subView.subviews {
if subsubView.isKindOfClass(UIButton) {
subsubView.tintColor = UIColor.whiteColor()
}
}
}
}
If I paste it in viewDidLoad, it doesn't work, cause I think Cancel button initialize only when SearchController becomes Active.
If I paste code in viewDidLayoutSubviews everything work great, but I'm not sure its a correct way.
So, where I should put this code in TableViewController?
Also, I don't understand, how I can receive notification in my TableViewController that SearchController becomes inactive. In other words where I should put code like this:
if self.resultSearchController.active == false {
//Do something
}
First you should insert delegate methods :-
class HomeViewController: UIViewController,UISearchResultsUpdating, UISearchBarDelegate {
var searchController: UISearchController!
override func viewDidLoad() {
super.viewDidLoad()
searchController = UISearchController(searchResultsController: nil)
searchController.searchResultsUpdater = self
searchController.dimsBackgroundDuringPresentation = false
searchController.searchBar.placeholder = "Search here..."
searchController.searchBar.delegate = self
searchController.searchBar.sizeToFit()
searchController.hidesNavigationBarDuringPresentation = true
tableView.tableHeaderView = searchController.searchBar
searchController.searchBar.tintColor = UIColor.whiteColor()
}
func searchBarTextDidBeginEditing(searchBar: UISearchBar) {
}
func searchBarCancelButtonClicked(searchBar: UISearchBar) {
}
func searchBarSearchButtonClicked(searchBar: UISearchBar) {
}
func updateSearchResultsForSearchController(searchController: UISearchController) {
}
}
then used delegate methods and change cancel button colors and thing what you want
You can try this in AppDelegate's didFinishLaunchWithOptions:.
UIBarButtonItem.appearanceWhenContainedInInstancesOfClasses([UISearchBar.self]).tintColor = UIColor.whiteColor()
PS: This is a generic method and would affect UIBarButtonItem in UISearchBar across app.
Swift 4.2, 4.0+ An answer is added here for a custom search bar that can be customized as below,
You can check the usage of SearchBar class.
Found a similar question to mine(this),
but my issues seems to be a bit more associated with view hierarchy.
I have a NSTextView, then as sibling views, several other NSViews on top of it.
Similar to the question linked above, I setup a tracking area, and applied the cursor as such:
class CursorChangingView: NSView {
override func updateTrackingAreas() {
let trackingArea = NSTrackingArea(rect:
}
override func cursorUpdate(event: NSEvent) {
NSCursor.arrowCursor().set()
}
}
It does seem to work when hovering, but immediately goes back to the IBeam Cursor, which is the default cursor for NSTextViews under this CursorChangingView.
Is this the proper way of applying changing the cursor when hovering over a certain NSView, and is the NSTextView under it overriding my overrriding?
All you need is to subclass a custom view, override awakeFromNib method, add the custom tracking area for [.mouseMoved, .activeAlways] events: NSTrackingArea Info there. There is no need to override resetCursorRects and/or updateTrackingAreas. All you need is to override mouseMoved method and set the desired cursor there:
Note about discardCursorRects method:
From the docs
You need never invoke this method directly
Xcode 9 • Swift 4
import Cocoa
class CursorChangingView: NSView {
override func awakeFromNib() {
addTrackingArea(NSTrackingArea(rect: bounds, options: [.activeAlways, .mouseMoved], owner: self, userInfo: nil))
wantsLayer = true
layer?.backgroundColor = NSColor.cyan.cgColor
layer?.borderColor = NSColor.black.cgColor
layer?.borderWidth = 1
}
#objc override func mouseMoved(with theEvent: NSEvent) {
NSCursor.pointingHand.set()
}
}
Sample
Thanks #Leo Dabus for your answer,
but I managed to solve it, so I will post my answer too.
In my case, for some reason, mouseEntered and mouseEntered did not work at all.
So here is my code that finally got it to work:
class CursorChangingView: NSView {
let trackingArea: NSTrackingArea?
func setupTracking() {
if self.trackingArea == nil {
self.trackingArea = NSTrackingArea(rect: self.bounds, options: NSTrackingAreaOptions.ActiveAlways | NSTrackingAreaOptions.MouseMoved | NSTrackingAreaOptions.CursorUpdate | NSTrackingAreaOptions.MouseEnteredAndExited | NSTrackingAreaOptions.ActiveInActiveApp, owner: self, userInfo: nil)
self.addTrackingArea(self.trackingArea!)
}
}
override func updateTrackingAreas() {
self.trackingArea = NSTrackingArea(rect: self.bounds, options: NSTrackingAreaOptions.ActiveAlways | NSTrackingAreaOptions.CursorUpdate | NSTrackingAreaOptions.MouseEnteredAndExited | NSTrackingAreaOptions.ActiveInActiveApp, owner: self, userInfo: nil)
self.addTrackingArea(self.trackingArea!)
}
override func resetCursorRects() {
self.discardCursorRects()
self.addCursorRect(self.bounds, cursor: NSCursor.arrowCursor())
}
override func mouseMoved(theEvent: NSEvent) {
NSCursor.arrowCursor().set()
}
}
It might be a little excessive, but worked, so will share this as my own solution.
A few important notes:
Be careful calling super on your mouseMoved or similar events, or the cursor might just get reset by the base class implementation.
Only reset your tracking area when the parent view size changes; if you try to do this by overriding layout() it's going to be happening all the time which is not great
Here's an example class that you can just use as a base class in your storyboards.
Swift 4 code:
import Cocoa
final class MouseTrackingTextView: NSTextView {
// MARK: - Lifecycle
override func awakeFromNib() {
setupTrackingArea()
}
// MARK: - Resizing
// Call this in your controller's `viewDidLayout`
// so it only gets called when the view resizes
func superviewResized() {
resetTrackingArea()
}
// MARK: - Mouse Events
override func resetCursorRects() {
addCursorRect(bounds, cursor: cursorType)
}
override func mouseMoved(with event: NSEvent) {
cursorType.set()
}
// MARK: - Private Properties
private var currentTrackingArea: NSTrackingArea?
private var cursorType: NSCursor {
return isEditable ? .iBeam : .pointingHand
}
// MARK: - Private API
private func setupTrackingArea() {
let trackingArea = NSTrackingArea(rect: bounds,
options: [.activeAlways, .mouseMoved],
owner: self, userInfo: nil)
currentTrackingArea = trackingArea
addTrackingArea(trackingArea)
}
private func resetTrackingArea() {
if let trackingArea = currentTrackingArea {
removeTrackingArea(trackingArea)
}
setupTrackingArea()
}
}
How does one go about making a delegate, i.e. NSUserNotificationCenterDelegate in swift?
Here's a little help on delegates between two view controllers:
Step 1: Make a protocol in the UIViewController that you will be removing/will be sending the data.
protocol FooTwoViewControllerDelegate:class {
func myVCDidFinish(_ controller: FooTwoViewController, text: String)
}
Step2: Declare the delegate in the sending class (i.e. UIViewcontroller)
class FooTwoViewController: UIViewController {
weak var delegate: FooTwoViewControllerDelegate?
[snip...]
}
Step3: Use the delegate in a class method to send the data to the receiving method, which is any method that adopts the protocol.
#IBAction func saveColor(_ sender: UIBarButtonItem) {
delegate?.myVCDidFinish(self, text: colorLabel.text) //assuming the delegate is assigned otherwise error
}
Step 4: Adopt the protocol in the receiving class
class ViewController: UIViewController, FooTwoViewControllerDelegate {
Step 5: Implement the delegate method
func myVCDidFinish(_ controller: FooTwoViewController, text: String) {
colorLabel.text = "The Color is " + text
controller.navigationController.popViewController(animated: true)
}
Step 6: Set the delegate in the prepareForSegue:
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "mySegue" {
let vc = segue.destination as! FooTwoViewController
vc.colorString = colorLabel.text
vc.delegate = self
}
}
And that should work. This is of course just code fragments, but should give you the idea. For a long explanation of this code you can go over to my blog entry here:
segues and delegates
If you are interested in what's going on under the hood with a delegate I did write on that here:
under the hood with delegates
Delegates always confused me until I realized that a delegate is just a class that does some work for another class. It's like having someone else there to do all the dirty work for you that you don't want to do yourself.
I wrote a little story to illustrate this. Read it in a Playground if you like.
Once upon a time...
// MARK: Background to the story
// A protocol is like a list of rules that need to be followed.
protocol OlderSiblingDelegate: class {
// The following command (ie, method) must be obeyed by any
// underling (ie, delegate) of the older sibling.
func getYourNiceOlderSiblingAGlassOfWater()
}
// MARK: Characters in the story
class BossyBigBrother {
// I can make whichever little sibling is around at
// the time be my delegate (ie, slave)
weak var delegate: OlderSiblingDelegate?
func tellSomebodyToGetMeSomeWater() {
// The delegate is optional because even though
// I'm thirsty, there might not be anyone nearby
// that I can boss around.
delegate?.getYourNiceOlderSiblingAGlassOfWater()
}
}
// Poor little sisters have to follow (or at least acknowledge)
// their older sibling's rules (ie, protocol)
class PoorLittleSister: OlderSiblingDelegate {
func getYourNiceOlderSiblingAGlassOfWater() {
// Little sis follows the letter of the law (ie, protocol),
// but no one said exactly how she had to respond.
print("Go get it yourself!")
}
}
// MARK: The Story
// Big bro is laying on the couch watching basketball on TV.
let bigBro = BossyBigBrother()
// He has a little sister named Sally.
let sally = PoorLittleSister()
// Sally walks into the room. How convenient! Now big bro
// has someone there to boss around.
bigBro.delegate = sally
// So he tells her to get him some water.
bigBro.tellSomebodyToGetMeSomeWater()
// Unfortunately no one lived happily ever after...
// The end.
In review, there are three key parts to making and using the delegate pattern.
the protocol that defines what the worker needs to do
the boss class that has a delegate variable, which it uses to tell the worker class what to do
the worker class that adopts the protocol and does what is required
Real life
In comparison to our Bossy Big Brother story above, delegates are often used for the following practical applications:
Communication: one class needs to send some information to another class.
Code example 1: sending data from one view controller to another
Code example 2: sending text input from a custom keyboard to a text field
Customization: one class wants to allow another class to customize it.
The great part is that these classes don't need to know anything about each other beforehand except that the delegate class conforms to the required protocol.
I highly recommend reading the following two articles. They helped me understand delegates even better than the documentation did.
What is Delegation? – A Swift Developer’s Guide
How Delegation Works – A Swift Developer’s Guide
One more note
Delegates that reference other classes that they do not own should use the weak keyword to avoid strong reference cycles. See this answer for more details.
It is not that different from obj-c.
First, you have to specify the protocol in your class declaration, like following:
class MyClass: NSUserNotificationCenterDelegate
The implementation will look like following:
// NSUserNotificationCenterDelegate implementation
func userNotificationCenter(center: NSUserNotificationCenter, didDeliverNotification notification: NSUserNotification) {
//implementation
}
func userNotificationCenter(center: NSUserNotificationCenter, didActivateNotification notification: NSUserNotification) {
//implementation
}
func userNotificationCenter(center: NSUserNotificationCenter, shouldPresentNotification notification: NSUserNotification) -> Bool {
//implementation
return true
}
Of course, you have to set the delegate. For example:
NSUserNotificationCenter.defaultUserNotificationCenter().delegate = self;
I got few corrections to post of #MakeAppPie
First at all when you are creating delegate protocol it should conform to Class protocol. Like in example below.
protocol ProtocolDelegate: class {
func myMethod(controller:ViewController, text:String)
}
Second, your delegate should be weak to avoid retain cycle.
class ViewController: UIViewController {
weak var delegate: ProtocolDelegate?
}
Last, you're safe because your protocol is an optional value. That means its "nil" message will be not send to this property. It's similar to conditional statement with respondToselector in objC but here you have everything in one line:
if ([self.delegate respondsToSelector:#selector(myMethod:text:)]) {
[self.delegate myMethod:self text:#"you Text"];
}
Above you have an obj-C example and below you have Swift example of how it looks.
delegate?.myMethod(self, text:"your Text")
Here's a gist I put together. I was wondering the same and this helped improve my understanding. Open this up in an Xcode Playground to see what's going on.
protocol YelpRequestDelegate {
func getYelpData() -> AnyObject
func processYelpData(data: NSData) -> NSData
}
class YelpAPI {
var delegate: YelpRequestDelegate?
func getData() {
println("data being retrieved...")
let data: AnyObject? = delegate?.getYelpData()
}
func processYelpData(data: NSData) {
println("data being processed...")
let data = delegate?.processYelpData(data)
}
}
class Controller: YelpRequestDelegate {
init() {
var yelpAPI = YelpAPI()
yelpAPI.delegate = self
yelpAPI.getData()
}
func getYelpData() -> AnyObject {
println("getYelpData called")
return NSData()
}
func processYelpData(data: NSData) -> NSData {
println("processYelpData called")
return NSData()
}
}
var controller = Controller()
DELEGATES IN SWIFT 2
I am explaining with example of Delegate with two viewControllers.In this case, SecondVC Object is sending data back to first View Controller.
Class with Protocol Declaration
protocol getDataDelegate {
func getDataFromAnotherVC(temp: String)
}
import UIKit
class SecondVC: UIViewController {
var delegateCustom : getDataDelegate?
override func viewDidLoad() {
super.viewDidLoad()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
// Dispose of any resources that can be recreated.
}
#IBAction func backToMainVC(sender: AnyObject) {
//calling method defined in first View Controller with Object
self.delegateCustom?.getDataFromAnotherVC(temp: "I am sending data from second controller to first view controller.Its my first delegate example. I am done with custom delegates.")
self.navigationController?.popViewControllerAnimated(true)
}
}
In First ViewController Protocol conforming is done here:
class ViewController: UIViewController, getDataDelegate
Protocol method definition in First View Controller(ViewController)
func getDataFromAnotherVC(temp : String)
{
// dataString from SecondVC
lblForData.text = dataString
}
During push the SecondVC from First View Controller (ViewController)
let objectPush = SecondVC()
objectPush.delegateCustom = self
self.navigationController.pushViewController(objectPush, animated: true)
First class:
protocol NetworkServiceDelegate: class {
func didCompleteRequest(result: String)
}
class NetworkService: NSObject {
weak var delegate: NetworkServiceDelegate?
func fetchDataFromURL(url : String) {
delegate?.didCompleteRequest(result: url)
}
}
Second class:
class ViewController: UIViewController, NetworkServiceDelegate {
let network = NetworkService()
override func viewDidLoad() {
super.viewDidLoad()
network.delegate = self
network.fetchDataFromURL(url: "Success!")
}
func didCompleteRequest(result: String) {
print(result)
}
}
Very easy step by step (100% working and tested)
step1: Create method on first view controller
func updateProcessStatus(isCompleted : Bool){
if isCompleted{
self.labelStatus.text = "Process is completed"
}else{
self.labelStatus.text = "Process is in progress"
}
}
step2: Set delegate while push to second view controller
#IBAction func buttonAction(_ sender: Any) {
let secondViewController = self.storyboard?.instantiateViewController(withIdentifier: "secondViewController") as! secondViewController
secondViewController.delegate = self
self.navigationController?.pushViewController(secondViewController, animated: true)
}
step3: set delegate like
class ViewController: UIViewController,ProcessStatusDelegate {
step4: Create protocol
protocol ProcessStatusDelegate:NSObjectProtocol{
func updateProcessStatus(isCompleted : Bool)
}
step5: take a variable
var delegate:ProcessStatusDelegate?
step6: While go back to previous view controller call delegate method so first view controller notify with data
#IBAction func buttonActionBack(_ sender: Any) {
delegate?.updateProcessStatus(isCompleted: true)
self.navigationController?.popViewController(animated: true)
}
#IBAction func buttonProgress(_ sender: Any) {
delegate?.updateProcessStatus(isCompleted: false)
self.navigationController?.popViewController(animated: true)
}
Simple Example:
protocol Work: class {
func doSomething()
}
class Manager {
weak var delegate: Work?
func passAlong() {
delegate?.doSomething()
}
}
class Employee: Work {
func doSomething() {
print("Working on it")
}
}
let manager = Manager()
let developer = Employee()
manager.delegate = developer
manager.passAlong() // PRINTS: Working on it
Delegates are a design pattern that allows one object to send messages to another object when a specific event happens.
Imagine an object A calls an object B to perform an action. Once the action is complete, object A should know that B has completed the task and take necessary action, this can be achieved with the help of delegates!
Here is a tutorial implementing delegates step by step in swift 3
Tutorial Link
Here is real life delegate scenario
Lets make our own UITextField and UITextFieldDelegate
// THE MYSTERIOUS UITEXTFIELD
protocol UITextFieldDelegate {
func textFieldDidChange(_ textField: UITextField) -> Void
}
class UITextField {
var delegate: UITextFieldDelegate?
private var mText: String?
var text: String? {
get {
return mText
}
}
init(text: String) {
}
init() {
}
func setText(_ text: String) {
mText = text
delegate?.textFieldDidChange(self)
}
}
// HERE IS MY APP
class Main {
let textfield = UITextField()
func viewDidLoad() {
print("viewDidLoad")
textfield.delegate = self
textfield.setText("Hello")
}
}
extension Main: UITextFieldDelegate {
func textFieldDidChange(_ textField: UITextField) {
print(textField.text ?? "No string")
}
}
let main = Main()
main.viewDidLoad()
Here Simple Code Example of Delegate:
//MARK: - Protocol ShowResult
protocol ShowResult: AnyObject {
func show(value: Int)
}
//MARK: - MyOperation Class
class MyOperation {
weak var delegate: ShowResult?
func sum(fNumber: Int, sNumber: Int) {
delegate?.show(value: fNumber + sNumber)
}
}
//MARK: - ViewController Class
class ViewController: UIViewController,ShowResult {
var myOperation: MyOperation?
override func viewDidLoad() {
super.viewDidLoad()
loadMyOperation()
myOperation?.delegate = self
myOperation?.sum(fNumber: 100, sNumber: 20)
}
private func loadMyOperation() {
if myOperation == nil {
myOperation = MyOperation()
}
}
func show(value: Int) {
print("value: \(value)")
}
}
The solutions above seemed a little coupled and at the same time avoid reuse the same protocol in other controllers, that's why I've come with the solution that is more strong typed using generic type-erasure.
#noreturn public func notImplemented(){
fatalError("not implemented yet")
}
public protocol DataChangedProtocol: class{
typealias DataType
func onChange(t:DataType)
}
class AbstractDataChangedWrapper<DataType> : DataChangedProtocol{
func onChange(t: DataType) {
notImplemented()
}
}
class AnyDataChangedWrapper<T: DataChangedProtocol> : AbstractDataChangedWrapper<T.DataType>{
var base: T
init(_ base: T ){
self.base = base
}
override func onChange(t: T.DataType) {
base.onChange(t)
}
}
class AnyDataChangedProtocol<DataType> : DataChangedProtocol{
var base: AbstractDataChangedWrapper<DataType>
init<S: DataChangedProtocol where S.DataType == DataType>(_ s: S){
self.base = AnyDataChangedWrapper(s)
}
func onChange(t: DataType) {
base.onChange(t)
}
}
class Source : DataChangedProtocol {
func onChange(data: String) {
print( "got new value \(data)" )
}
}
class Target {
var delegate: AnyDataChangedProtocol<String>?
func reportChange(data:String ){
delegate?.onChange(data)
}
}
var source = Source()
var target = Target()
target.delegate = AnyDataChangedProtocol(source)
target.reportChange("newValue")
output: got new value newValue
In swift 4.0
Create a delegate on class that need to send some data or provide some functionality to other classes
Like
protocol GetGameStatus {
var score: score { get }
func getPlayerDetails()
}
After that in the class that going to confirm to this delegate
class SnakesAndLadders: GetGameStatus {
func getPlayerDetails() {
}
}
In swift 5
I am a beginner, I think this is easiest way to understand in practical scenario
Note:Any improvisations are most appreciated
protocol APIService {
func onSuccessResponse() -> AnyObject
func onFailureResponse() -> AnyObject
}
class APIHelper{
var delegate : APIService?
func postUsersDataAPI() {
//assuming API communication is success
if(success){
let _: AnyObject? = delegate?.onSuccessResponse()
}else if(failure){
let _: AnyObject? = delegate?.onFailureResponse()
}
}
func getAllUsersAPI() {
//assuming API communication is success
if(success){
let _: AnyObject? = delegate?.onSuccessResponse()
}else if(failure){
let _: AnyObject? = delegate?.onFailureResponse()
}
}
}
class ViewController:UIViewController,APIService {
func onSuccessResponse() -> AnyObject {
print("onSuccessResponse") as AnyObject
}
func onFailureResponse() -> AnyObject {
print("onFailureResponse") as AnyObject
}
#IBAction func clickBtnToPostUserData(_ sender: Any) {
let apiHelper = APIHelper()
apiHelper.delegate = self
apiHelper.postAPI()
}