I want to perform segue from View B to View C and I am calling method in class A.
My segue method in Class B is-
//ViewController B
func nextViewAction() -> Void {
self.performSegueWithIdentifier("nextview", sender: self)
}
And I am calling it in Class A like this-
//ViewController A
#IBAction func sideMenuAction(sender: AnyObject) {
ViewClassB().nextViewAction()
}
But it crashing- Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Receiver () has no segue with identifier 'nextview''
Have you set the name nextview for the segue between Controller B and Controller C? You can check by clicking on the segue between the two controllers, and then checking the Identifier value in the Attributes Inspector.
What you can have is move to the third viewcontroller from first viewcontroller by skipping the second one use the code below..
class MyViewController: UIViewController, UINavigationControllerDelegate {
var viewControllerToInsertBelow : UIViewController?
override func viewDidLoad() {
super.viewDidLoad()
self.navigationController?.delegate = self
}
func pushTwoViewControllers() {
if let viewController2 = self.storyboard?.instantiateViewControllerWithIdentifier("id1"),
let viewController3 = self.storyboard?.instantiateViewControllerWithIdentifier("id2") { //change this to your identifiers
self.viewControllerToInsertBelow = viewController2
self.navigationController?.pushViewController(viewController3, animated: true)
}
}
//MARK: - UINavigationControllerDelegate
func navigationController(navigationController: UINavigationController, didShowViewController viewController: UIViewController, animated: Bool) {
if let vc = viewControllerToInsertBelow {
viewControllerToInsertBelow = nil
let index = navigationController.viewControllers.indexOf(viewController)!
navigationController.viewControllers.insert(vc, atIndex: index)
}
}
}
Reference : SO Post
Don't need to do any other code just use
notification observer it will solve your problem.
Thank you
I think you cannot trigger segue action from AViewController because what
performSegue does is that :
Initiates the segue with the specified identifier from the current view controller's storyboard file.
Try implementing segue from A to C
Related
Setup: table view controller has button (Add) that pops up another view controller with a form. I'm using Realm to store data, so no need to pass data back. However, when I dismiss() the view controller, and return to the table view controller, I cannot get tableView.reloadData() to work.
I have tried viewWillAppear() and viewDidAppear() but neither appear to be in the call stack.
Any ideas where I need to put this?
You need a delegate
let second = ///
second.delegate = self
When you dismiss in 2nd vc
delegate?.refresh()
Probably your second controller is being displayed modally. According to Apple Developer Documentation:
If a view controller is presented by a view controller inside of a popover, this method is not invoked on the presenting view controller after the presented controller is dismissed.
You can solve your problem with a delegate:
protocol ControllerBDelegate {
func willDismiss()
}
class ControllerA {
func open() {
let vc = ControllerB()
vc.delegate = self
self.present(vc, animated: true)
}
}
extension ControllerA : ControllerBDelegate {
func willDismiss() {
self.tableView.reloadData()
}
}
class ControllerB {
weak var delegate: ControllerBDelegate?
override func viewWillDisappear(_ animated: Bool) {
super.viewWillDisappear(animated)
delegate?.willDismiss()
}
}
I'm quite new with Swift and I'm making this mini game type app that counts the score and updates the label in the view controller. I want to pass that score from a view controller into another external pop up view controller I created.
#IBAction func Button7Tapped(_ sender: AnyObject)
{
if Index == 13 {
game.score += 1
} else {
let scorepopVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "finalScorePop") as! finalScoreViewController
self.addChildViewController(scorepopVC)
scorepopVC.view.frame = self.view.frame
self.view.addSubview(scorepopVC.view)
scorepopVC.didMove(toParentViewController: self)
}
updateGame()
}
Above is my code for the external pop up view controller I created, which also has a separated .swift file. How would I go about taking my game.score and passing that into my Popup view controller?
In your finalScoreViewController swift file add a new property.
final class FinalScoreViewController: UIViewController {
var score: Int?
}
And then just assign it when you're instantiating it.
#IBAction func Button7Tapped(_ sender: AnyObject) {
if Index == 13 {
game.score += 1
} else {
let scorepopVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "finalScorePop") as! finalScoreViewController
scorepopVC.score = game.score //THIS LINE
self.addChildViewController(scorepopVC)
scorepopVC.view.frame = self.view.frame
self.view.addSubview(scorepopVC.view)
scorepopVC.didMove(toParentViewController: self)
}
updateGame()
}
It is better to use storyboard to open the ViewController. In storyboard, right click and drag from you button to the second view controller (the one that you wish to open).
Choose the segue type that you wish to use. In your case, I think Present Modally will work fine.
You will see a line between the two UIViewControllers in storyboard. That is the segue. Tap on it. In the Attributes inspector give the segue an identifier. For instance "myFirstSegue".
Then in the code of the UIViewController that contains your button override prepare(for:sender:). This method is called when preparing for the segue to happen. I.o.w when you tap on the button. You have access to the destination UIViewController and can therefor access and set the properties on it.
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "myFirstSegue" {
if let vc = segue.destination as? MyViewController {
//here you set your data on the destination view controller
vc.myString = "Hello World"
}
}
}
Note that we check the identifier, because all segues that go from this ViewController to other ViewControllers will call prepare(for:sender:)
It's quite simple, Just add a property in your finalScoreViewController (if you are not already done this) and -for example- call it score:
class finalScoreViewController: UIViewController {
var score: String?
// ...
Add this line to the Button7Tapped action (where you set a value for finalScoreViewController's score):
let scorepopVC = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "finalScorePop") as! finalScoreViewController
// add this line:
scorepopVC.score = "My score"
self.addChildViewController(scorepopVC)
scorepopVC.view.frame = self.view.frame
self.view.addSubview(scorepopVC.view)
scorepopVC.didMove(toParentViewController: self)
Finally, in finalScoreViewController:
override func viewDidLoad() {
super.viewDidLoad()
if let scr = score {
print(scr)
}
}
Hope that helped.
You do not actually have to pass the variable to the next view controller. All you have to do is create a variable outside of the View Controller class, and voila, you can access your variable from anywhere, in any swift file. For example:
var score = 0
class ViewController: UIViewController {
override func viewDidLoad(){
super.viewDidLoad()
}
#IBAction func Button7Tapped(_ sender: AnyObject){
score += 1
}
}
And then in the other View Controller, you would have something like this:
#IBOutlet weak var scoreLabel: UILabel!
class ViewController: UIViewController {
override func viewDidLoad(){
super.viewDidLoad()
var timer1 = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(updateScore), userInfo: nil, repeats: true)
}
#objc func updateScore() {
scoreLabel.text = "You have \(score) points!"
}
I have 3 UIViewControllers say:
v1ViewController
v2ViewController
v3ViewController.
I have pushed controllers as v2 on v1 and v3 on v2.
Now I want to bring some value back to v1ViewController from v3ViewController using delegates.
On v3Viewcontroller I wrote it:
for vc in self.navigationController!.viewControllers{
if vc is v1ViewController{
delegate?.returnFilteredImage(imageView.image!)
self.navigationController?.popToViewController(vc, animated: true)
}
}
How can I use delegates because in v1ViewController I haven't create object of v3Viewcontroller; consequently I cannot connect delegate to self.
So how can i do that.
1. Using delgates
create a protocol and implement in your firstviewcontroller
protocol My {
func returnFilteredImage(image: UIImage)
}
class FirstViewController: UIViewcontroller, My {
...
func returnFilteredImage(image: UIImage) {
}
}
and in your thirdViewController create a property and assign FirstViewController delegate to this.
class ThirdViewController: UIViewController {
var delegate: My?
...
override func viewDidLoad() {
super.viewDidLoad()
for vc in self.navigationController!.viewControllers{
if vc is FirstViewController {
let vc1 = vc as! FirstViewController
self.delegate = vc1
self.delegate?.returnFilteredImage(imageView.image!)
self.navigationController?.popToViewController(vc, animated: true)
}
}
}
}
2. Using local notifications
check here
You can do this using local notifications
class FirstViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
//add observer
NSNotificationCenter.defaultCenter().addObserver(self, selector: #selector(self.didgetImage(_:)), name: "receiveImageNotification", object: nil)
}
func didgetImage(notification: NSNotification) {
if let image = notification.userInfo?["image"] as? UIImage {
// do something with your image
}
}
}
and from third view controller, first notification
let imageDataDict:[String: UIImage] = ["image": image]
NSNotificationCenter.defaultCenter().postNotificationName("receiveImageNotification", object: self, userInfo: imageDataDict)
Hope this helps :)
I'm trying to realize the Observer Pattern and I'm experiencing some difficulty as my delegate doesn't seem to be setting properly.
In my Main.storyboard I have a ViewController with a container view. I also have an input box where I'm capturing numbers from a number keypad.
Here's my storyboard:
I'm trying to implement my own Observer Pattern using a protocol that looks like this:
protocol PropertyObserverDelegate {
func willChangePropertyValue(newPropertyValue:Int)
func didChangePropertyValue(oldPropertyValue:Int)
}
My main ViewController.swift
class ViewController: UIViewController {
#IBOutlet weak var numberField: UITextField!
// observer placeholder to be initialized in implementing controller
var observer : PropertyObserverDelegate?
var enteredNumber: Int = 0 {
willSet(newValue) {
print("//Two: willSet \(observer)") // nil !
observer?.willChangePropertyValue(5) // hard coded value for testing
}
didSet {
print("//Three: didSet")
observer?.didChangePropertyValue(5) // hard coded value for testing
}
}
#IBAction func numbersEntered(sender: UITextField) {
guard let inputString = numberField.text else {
return
}
guard let number : Int = Int(inputString) else {
return
}
print("//One: \(number)")
self.enteredNumber = number // fires my property observer
}
}
My ObservingViewController:
class ObservingViewController: UIViewController, PropertyObserverDelegate {
// never fires!
func willChangePropertyValue(newPropertyValue: Int) {
print("//four")
print(newPropertyValue)
}
// never fires!
func didChangePropertyValue(oldPropertyValue: Int) {
print("//five")
print(oldPropertyValue)
}
override func viewDidLoad() {
super.viewDidLoad()
print("view loads")
// attempting to set my delegate
let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
let pvc = mainStoryboard.instantiateViewControllerWithIdentifier("ViewController") as! ViewController
print("//six \(pvc)")
pvc.observer = self
}
}
Here's what my console prints:
What's happening
As you can see when my willSet fires, my observer is nil which indicates that I have failed to set my delegate in my ObservingViewController. I thought I set my delegate using these lines:
let mainStoryboard: UIStoryboard = UIStoryboard(name: "Main", bundle: nil)
let pvc = mainStoryboard.instantiateViewControllerWithIdentifier("ViewController") as! ViewController
print("//six \(pvc)")
pvc.observer = self
However, I must be setting my delegate incorrectly if it's coming back nil.
Question
How do I properly set my delegate?
You are calling into the storyboard to instantiate a view controller and setting it as the observer, however that instantiates a new instance of that view controller, it doesn't mean that it is referencing the one single "view controller" that is in the storyboard. ObservingViewController needs another way to reference the ViewController that has already been created.
So #Chris did reenforce my suspicions which helped me to figure out a solution for assigning my delegate to my view controller properly.
In my ObservingViewController I just need to replace the code in my viewDidLoad with the following:
override func viewDidLoad() {
let app = UIApplication.sharedApplication().delegate as! AppDelegate
let vc = app.window?.rootViewController as! ViewController
vc.observer = self
}
Rather than creating a new instance of my view controller, I'm now getting my actual view controller.
I have got two ViewControllers. One is "ViewController", the second is "SecondViewController".
On the ViewController, I have var player = AVAudioPlayer(). I have loaded and played BGM there successfully, and then I pushed the SecondViewController into view.
On the SecondViewController, I used this code to stop the audio player on the ViewController:
let viewController = self.storyboard?.instantiateViewControllerWithIdentifier("ViewController") as? ViewController
viewController?.player.pause()
But I get error Thread 1: EXC_BAD_ACCESS (code=1, address=0x38)
From what I learned from browsing around, this happened because I tried to access the player while the player hasn't been initialized yet.
But how it can be? Hasn't it been initialized already? The music is still playing up to when this error occurs. What's wrong and how to fix it so that I can manipulate audio player from a different ViewController than the currently active one (but it's already active in background)? Thanks.
You are instantiating a new view controller; not using the same view controller that presented SecondViewController and so AudioPlayer that gets created is not same as the previous AudioPlayer. You should somehow refer to the presenting view controller.
One way to do would be by what is called a delegate pattern,
class ViewController: UIViewController {
...
func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "SecondViewController" {
if let secondViewController = segue.destinationViewController as? SecondViewController {
secondViewController.delegate = self
}
}
}
// MARK: SecondViewControllerDelegate
func stopPlayer() {
player.stopPlayer()
}
}
protocol SecondViewControllerDelegate {
func stopPlayer()
}
class SecondViewController: UIViewController {
...
var delegate: SecondViewControllerDelegate?
func stopPlayer() {
delegate?.stopPlayer()
}
}
Or, then, you can also pass AVPlayer from first view controller to SecondViewController and use it to stop from SecondViewController itself,
class ViewController: UIViewController {
...
func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "SecondViewController" {
if let secondViewController = segue.destinationViewController as? SecondViewController {
secondViewController.player = self.player
}
}
}
}
class SecondViewController: UIViewController {
...
var player: AVPlayer!
func stop() {
player.stop()
}
}
instantiateViewControllerWithIdentifier creates a new instance of your view controller.
Instead put a property on secondViewController of type YourViewController and set that in the prepareForSegue in YourViewController.
The problem is that instantiateViewControllerWithIdentifier creates a new ViewController. It doesn't return the one that you've been on. Anyway, trying to access something on a previous view controller doesn't seem like a good design to me.
One option is to pass AVAudioPlayer to your second VC in prepareForSegue method. You can declare an AVAudioPlayer property and set it there.