I have a view controller (containing my menu) presented on top of another view controller (my application).
I would need to access the presenting view controller (below my menu) from the presented view controller (my menu), for example to access some variables or make the presenting view controller perform one of its segues.
However, I just can't figure out how to do it.
I'm aware of the "presentingViewController" and "presentedViewController" variables but I didn't manage to use them successfully.
Any Idea ?
Code (from the presented VC, which as a reference to the AppDelegate in which the window is referenced) :
if let presentingViewController = self.appDelegate.window?.rootViewController?.presentingViewController {
presentingViewController.performSegue(withIdentifier: "nameOfMySegue", sender: self)
}
Here is a use of the delegation Design pattern to talk back to the presenting view controller.
First Declare a protocol, that list out all the variables and methods a delegate is expected to respond to.
protocol SomeProtocol {
var someVariable : String {get set}
func doSomething()
}
Next : Make your presenting view controller conform to the protocol.
Set your presenting VC as the delegate
class MainVC: UIViewController, SomeProtocol {
var someVariable: String = ""
func doSomething() {
// Implementation of do
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
// Your code goes here.
if let destVC = segue.destination as? SubVC{
destVC.delegate = self
}
}
}
Finally, when you are ready to call a method on the presenting VC (Delegate).
class SubVC: UIViewController {
var delegate : SomeProtocol?
func whenSomeEventHappens() {
// For eg : When a menu item is selected
// Set some Variable
delegate?.someVariable = "Some Value"
// Call a method on the deleate
delegate?.doSomething()
}
}
Assuming that VCApplication is presenting VCMenu, in VCMenu you can access VCApplication with:
weak let vcApplication = self.presentingViewController as? VCApplicationType
Your example self.appDelegate.window?.rootViewController?.presentingViewController is looking for the ViewController that presented the rootViewController - it will be nil.
EDIT
Per TheAppMentor I've added weak so there are no retain cycles.
Related
I have two UIViewController: A, B
Lets say there are two segues connecting them: C, D
Once a segue has been activated and I am in view B, can I know which segue got me here? C or D?
I don't know of any built-in mechanism for this, but you could have all your destination view controllers conform to a protocol SourceSegueProtocol that has a var to contain the invoking segue.
Then in the source view controller's prepare(for:sender:) method you could set that variable for destination view controllers that conform to the SourceSegueProtocol.
There is a prepare(for: segue) function that allows you to set a property in the new ViewController.
class OriginViewController : UIViewController {
...
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if let destination = segue.destination as? SegueProtocol {
destination.transitionSegue = segue.identifier
}
}
}
class DestinationViewController : UIViewController, SegueProtocol {
var transitionSegue: String = ""
override func viewDidLoad() {
print("Segue: ", transitionSegue)
}
}
protocol SegueProtocol {
var transitionSegue : String { get set }
}
Edit: As per comment suggestion, it's better to expect a destination that conforms to a protocol rather than one of a specific type.
I'm having the hardest time finding an answer for this.
I have a xib view that is within a scrollview that is within a view controller. In the xib I have a button with an action and I need to segue to a view controller I have in my storyboard. I also would like to be able to use a custom segue.
So far, I have read that I can instantiate the viewcontroller from the storyboard to segue to it. But then I don't know how to present that controller.
thanks for any help...
UPDATE:
this is the code I'm using to perform the segue.
In parent ViewController:
static var referenceVC: UIViewController?
override func viewDidLoad() {
super.viewDidLoad()
print("viewdidload")
LevelSelectViewController.referenceVC = self
setupScrollView()
}
code in xib view file
let vc = UIStoryboard(name: "Main", bundle: nil).instantiateViewController(withIdentifier: "sightWordController")
let parent = LevelSelectViewController.referenceVC!
let segue = InFromRightCustomSegue(identifier: "test", source: parent, destination: vc)
segue.perform()
As noted in the comments, Segues are typically confined to storyboard usage as noted in the documentation. You can implement a custom xib view in a storyboard via #IBDesignable like approaches and have you're view load from the xib into the storyboard file/class. This way, you gain the benefits of both worlds. Otherwise, you may want to approach this in another fashion (such as delegates/target-action events, etc).
You may also climb the responder chain and call a segue related to the VC loaded from the storyboard (the segue doesn't necessarily have to be attached to any particular action) via getting a reference to the VC and calling the segue. You can climb the responder chain in a manner such as the example code below:
protocol ChildViewControllerContainer {
var parentViewController: UIViewController? { get }
}
protocol ViewControllerTraversable {
func viewController<T: UIViewController>() -> T?
}
extension UIView: ViewControllerTraversable {
func viewController<T: UIViewController>() -> T? {
var responder = next
while let currentResponder = responder {
guard responder is T else {
responder = currentResponder.next
continue
}
break
}
return responder as? T
}
}
extension UITableViewCell: ChildViewControllerContainer {
weak var parentViewController: UIViewController? {
return viewController() as UIViewController?
}
}
I am creating an application in which there are 6 view controller in storyboard. The thing is that data is shared between the default view controller and the first one ( say A and B) which i added. i am using the prepareforseque method for passing data. the problem started when i added two more view controller. lets say C and D i created two new swift files and changed the two view controller class name. i created a textbox and button in C and label in D. when i pressed the button, the value of the text field is not passing into the D view controller although i used the same methods and code which i used for A and B. do i have to do anything else when i want to pass data between two newly added view controller.
first viewcontroller in which when a button is pressed value 1 needed to be passed:
class PlaySelectMenu: UIViewController {
var value = Int()
#IBAction func twotofive(sender: AnyObject) {
value = 1
}
override func viewDidLoad() {
super.viewDidLoad()
}
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let nextView : PlayGameView = segue.destinationViewController as! PlayGameView
nextView.x = value
}
}
the second view controller which receive the value and print it
import Foundation
import UIKit
class PlayGameView: UIViewController{
var x = Int()
override func viewDidLoad() {
super.viewDidLoad()
print(x)
}
}
here i have added both the view controller from the object library and not working with the default one which is present in storyboard by default. i dont know why these two viewcontroller are not working. please help.
Regards Dev
One solution would be to write the data out to NSUserDefaults and then read it back from NSUserDefaults in the other view controller. Probably not the proper or correct way to share data between two view controllers, but it's been a reliable work around for me.
Other than that, you'd need to share your code so that we can see what's occurring.
Can you post also the code in your controllers C & D. And also if you have copy/paste the code inside your first two controllers into the two others, are you sure that in your prepareForSegue method you have changed the name of the destination segue ?
Assuming you have created the segue in Storyboard:
All you need is to do is put all of needed updates in prepareForSegue because twotofive is called after prepareForSegue.
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
value = 1
let nextView : PlayGameView = segue.destinationViewController as! PlayGameView
nextView.x = value
}
Since you have connected your segue from button click to view controller, when you press button segue is automatically called. Instead of connecting segue from button to VC, connect VC to VC. Then in button click method at the last add below line:
#IBAction func twotofive(sender: AnyObject) {
value = 1
self.performSegueWithIdentifier("<Name of the segue identifier>", sender: self)
}
This will call your prepareForSegue. If you are calling more then one VC using segue from a VC then you can use segue.identifier to check which VC was called as below
override func prepareForSegue(segue: UIStoryboardSegue!, sender: AnyObject!) {
if segue.identifier == "CVC" {
}
I asked that question before, and I got the solution to what he sought. Now, I need to amplify my question. Using delegates, how can I create a Delegate to the ViewController send data to the ContainerView and ContainerView send data to the ViewController?
Well, I don't know if this is entirely what you're looking for, but what I've always done in this situation is kept a record of each view controller inside the other's class.
For example if your container view has the embed segue with identifier "Embed Segue" then your classes might look like:
Superview Class
Class ViewControllerOne: UIViewController {
var data = "This is my data I may want to change"
var subView: ViewControllerTwo?
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "Embed Segue" {
let destinationVC = segue.destinationViewController as! ViewControllerTwo
destinationVC.superView = self
self.subView = destinationVC
}
}
}
Embedded Class
Class ViewControllerTwo: UIViewController {
var data = "This is the other view controller's copy of that data"
var superView: ViewControllerOne?
}
Then you can pass data between these View Controllers simply by referencing self.subView.data and self.superView.data respectively.
Edit: For ViewControllerTwo to pass data back to ViewControllerOne, it would then simply have to reference self.superView.data. e.g:
Class ViewControllerTwo: UIViewController {
var data = "This is the other view controller's copy of that data"
var superView: ViewControllerOne?
func passDataBack() {
self.superView.data = self.data
}
}
This would then update the data variable in the first view controller.
Sorry in advance that I can’t explain myself very well. I’m really new to programming and the topic of delegation still eludes me. I had some great help with this once before, but now I am trying to use a delegate in a different situation and I can’t get it right. I pieced together a bit of code that doesn’t work, and no matter how much I search I can’t find a way to fix it.
I have a view controller (MainController) with and embedded view controller (EmbeddedController) in a container view. I am trying to have a button in the embedded controller manipulate the container view (containerView).
EmbeddedController:
protocol ControllerDelegate {
func hideContainerView()
}
class EmbeddedController: UIViewController {
var delegate: VControllerDelegate?
#IBAction func button(sender: AnyObject) {
delegate?.hideContainerView()
}
}
MainController:
class MainController: UIViewController, ControllerDelegate {
#IBOutlet var containerView: UIView!
func hideContainerView() {
containerView.hidden = true
}
override func viewDidLoad() {
super.viewDidLoad()
var vc = EmbeddedController()
vc.delegate = self
}
}
Does anyone have any idea what I am doing wrong? And why this isn’t working?
What I ended up doing is adding this to the MainController:
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if (segue.identifier == "mySegue") {
let vc = segue.destinationViewController as! EmbeddedController
vc.delegate = self
}
}
In storyboard I selected the segue from the MainController to the EmbeddedController, and set the identifier to "mySegue".
Without the code above the delegate kept returning nil. I didn't look into this solution at first as I thought segues were only for transitioning between view controllers, and in my mind I didn't see the embedded controller as a transition. Maybe someone more knowledgable than me (which is practically anyone on here at this point) can explain how this is all fitting together.
In any case, this is how I solved my issue and hopefully someone else can benefit from this as well :)
First of all, to avoid strong reference cycles:
protocol ControllerDelegate: class {
func hideContainerView()
}
class EmbeddedController: UIViewController {
weak var delegate: ControllerDelegate?
And you haven't added your newly instantiated VC view to container view, and not added it as a child VC:
let vc = EmbeddedController()
vc.delegate = self
containerView.addSubview(vc.view)
self.addChildViewController(vc)
vc.didMoveToParentViewController(self)