I have a UICollectionViewCell class "ProductCell"; I am trying to access the current navigation controller in order to update a barbuttonicon. I have tried the following code as this is what I use in my other UIViewControllers:
let nav = self.navigationController as! MFNavigationController
nav.updateCartBadgeValue()
However it states that the
value of type ProductCell has no member navigationController
I am aware that this is not a UIViewController but surely you should be able to access the current navigation controller the same way?
I also know that you can access the navigation controller by using UIApplication in the following way:
let navigationController = application.windows[0].rootViewController as! UINavigationController
I am not sure if that is a good way of doing it though.
Any help is much appreciated
Thanks
UIResponder chain will help here.
You can search the responder chain to find the controller for any view
extension UIView {
func controller() -> UIViewController? {
if let nextViewControllerResponder = next as? UIViewController {
return nextViewControllerResponder
}
else if let nextViewResponder = next as? UIView {
return nextViewResponder.controller()
}
else {
return nil
}
}
func navigationController() -> UINavigationController? {
if let controller = controller() {
return controller.navigationController
}
else {
return nil
}
}
}
controller() will return the closest responder that is of type UIViewController
Then on the returned controller you just need to find its navigation controller. You can use navigationController() here.
The simplest way is to add a property to you cell class that weakly references a UINavigationController
weak var navigationController: UINavigationController?
you will need to assign it in your cellForRow(atIndexPath:_) method.
let cell = tableView.dequeueReusableCell(withIdentifier: "yourReuseID") as! YourCellClass
cell.navigationController = navigationController //will assign your viewController's navigation controller to the cell
return cell
Unless things change, this is a good way to do it. To give you an example of a messier solution... You could add a
let hostViewController:UIViewController
property to your cell and add an initializer to handle it
let cell = ProductCell(vc: self)
But I don't think that's a better way to do it. your suggestion works fine.
let navigationController = application.windows[0].rootViewController as! UINavigationController
Related
Is there any equivalent in Swift to RACObserve(self, presentingViewController)?
Or any other why to imitate this behaviour?
My issue is that I want to be notified whenever a view controller is "hidden" by another view controller. In objc what I'd do is to check if self.presentingViewController is nil.
Note that in this scenario there's no knowledge of which view controller is presented, so it's impossible to notify from within its viewDidAppear/viewDidDisappear.
As I understand your question: you need to to know which view controller is presented now and you need notification inviewDidAppear/viewDidDisappear.
So we can get this in several way.
The simple way is:
Get information of which is the top ViewController right now.
2.Call this method in your viewDidAppear/viewDidDisappear
Like this :
Get Which is The Top ViewController
func getTopViewController() -> UIViewController? {
if var topVC = UIApplication.shared.keyWindow?.rootViewController {
while let presentedViewController = topVC.presentedViewController {
topVC = presentedViewController
return topVC
}
return topVC
}
return nil
}
Call in viewDidAppear:
override func viewDidAppear(_ animated: Bool) {
super.viewDidAppear(true)
if let top = getTopViewController() {
print("topView Controller name \(top.title)")
top.view.backgroundColor = .red
}
}
Hope it will help you !
I'm trying to call a function on a root view controller from a popover view controller. The function below works but it seems there should be a better way:
func doSomethingInRoot() {
if let appDelegate = UIApplication.shared.delegate as? AppDelegate,
let currentRoot = appDelegate.window!.rootViewController as? RootViewController {
currentRoot.somefunction()
}
}
In the above code, doSomethingInRoot would be contained in the popover, and someFunction would be a function of RootViewController.
What I'm looking for is a way to pass someFunction to another function that contains the if let above, however, the problem is currentRoot is only assigned as a RootViewController within the above (i.e., doSomethingInRoot doesn't know that it's being passed a method of RootViewController instead of a generic function).
In writing this question, I realized that I could do the following, which feels pretty clean, but I'm still curious whether I can pass a method to a specific class as parameter.
func doSomethingInRoot() {
if let root = getRoot() {
root.someFunction()
}
}
func getRoot() -> RootViewController? {
if let appDelegate = UIApplication.shared.delegate as? AppDelegate,
let currentRoot = appDelegate.window!.rootViewController as? RootViewController {
return currentRoot
} else {
return nil
}
}
In your popover view controller, you could add a property like this to hold the reference to someFunction
var rootsSomeFunction: (()->Void)!
Then assign the reference when creating the popover VC whether it's in prepareForSegue, or after you instantiate if from storyboard...etc. I'd also move getRoot() to the App Delegate.
popoverVC.rootsSomeFunction = appDelegate.getRoot().someFunction().self
Finally, in your popover view controller, you can call it by the property like this:
self.rootsSomeFunction()
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?
}
}
What is the best way to pass a UInavigationController and also pass variables to a new viewController. I know how to do one or the other but not both at the same time. Thank you in advance
this is my current code
func(){
let vc = storyboard?.instantiateViewControllerWithIdentifier("messagesViewController") as! UINavigationController
let posts = self.postList[indexPath.row]
//this is the var that i want to past
//vc.previousViewMessageId = posts.postKey
self.presentViewController(vc, animated: true, completion: nil)
}
If I understand you correctly, you have a view controller that can present a second VC. And this VC is embedded in a UINavigationController. What you don't know how to do, is to pass data from the first VC, to the navigation controller, then to the second VC.
Here is a brute force solution. It's not beautiful, but it works anyway.
Make your own UINavigationController subclass:
class DataPasserController: UINavigationController {
var previousViewMessageId: SomeType?
override func viewDidLoad() {
if let vc = self.topViewController as? YourSecondViewController {
vc.previousViewMessageId = self.previousViewMessageId
}
}
}
Now you can add a navigation controller in the storyboard, set its class to DataPasserController, and connect the second VC to it as its root view controller.
Now suppose you have got an instance of DataPasserController by calling instantiateViewControllerWithIdentifier, you can do this:
yourDataPasserControllerInstance.previousViewMessageId = posts.postKey
And present the instance!
To pass a value to your Navigation Controller's Root View Controller, you access viewControllers[0] and cast it to the class of your Messages View Controller (the controller that has the previousViewMessageId property):
func () {
let messagesNC = storyboard?.instantiateViewControllerWithIdentifier("messagesViewController") as! UINavigationController
let messagesVC = messagesNC.viewControllers.first as! MessagesViewController
messagesVC.previousViewMessageId = postList[indexPath.row].postKey
presentViewController(messagesNC, animated: true, completion: nil)
}
What you have there is simply presenting a view controller... You are skipping the navigation controller.
What you need to do is present the new view controller inside the navigation controller. Once you have done that, it will show correctly. You can also pass the variables after you've created the vc variable.
This presents the new viewController (vc) within the navigation controller...
self.navigationController?.pushViewController(vc, animated: false)
This sets the variable in the new viewController (vc) (you are correct)
vc.previousViewMessageId = posts.postKey
So complete:
func(){
let vc = storyboard?.instantiateViewControllerWithIdentifier("messagesViewController") as! MessagesViewController
let posts = self.postList[indexPath.row]
//this is the var that i want to past
vc.previousViewMessageId = posts.postKey
navigationController?.pushViewController(vc, animated: false)
}
PS. While not part of the question, I feel I should still mention... Use of the word self should be left to necessity only. In other words, don't use it when it isn't needed. for example self.postList[indexPath.row] :)
https://github.com/raywenderlich/swift-style-guide#use-of-self
I have an optional bool variable called showSettings on my first view controller which is called ViewController, and I'm popping from SecondViewController back to ViewController.
Before I pop, I want to set the bool to true. Seems wrong to instantiate another view controller since ViewController is in memory.
What's the best way to do this? I'm not using storyboards, if that's important for your answer.
Thanks for your help
So I figured it out, based mostly from this post – http://makeapppie.com/2014/09/15/swift-swift-programmatic-navigation-view-controllers-in-swift/
In SecondViewController, above the class declaration, add this code:
protocol SecondVCDelegate {
func didFinishSecondVC(controller: SecondViewController)
}
Then inside of SecondViewContoller add a class variable:
var delegate: MeditationVCDelegate! = nil
Then inside of your function that your button targets, add this:
self.navigationController?.popViewControllerAnimated(true)
delegate.didFinishSecondVC(self)
What we're doing here is doing the pop in SecondViewController, and not passing any data, but since we've defined a protocol, we're going to use that in ViewController to handle the data.
So next, in ViewController, add the protocol you defined in SecondViewController to the list of classes ViewController inherits from:
class ViewController: UIViewController, SecondVCDelegate { ... your code... }
You'll need to add the function we defined in the new protocol in order to make the compiler happy. Inside of ViewController's class, add this:
func didFinishSecondVC(controller: SecondViewController) {
self.myBoolVar = true
controller.navigationController?.popViewControllerAnimated(true)
}
In SecondViewController where we're calling didFinishSecondVC, we're calling this method inside of the ViewController class, the controller we're popping to. It's similar to if we wrote this code inside of SecondViewController but we've written it inside of ViewController and we're using a delegate to manage the messaging between the two.
Finally, in ViewController, in the function we're targeting to push to SecondViewController, add this code:
let secondVC = secondViewController()
secondVC.delegate = self
self.navigationController?.pushViewController(secondVC, animated: true)
That's it! You should be all set to pass code between two view controllers without using storyboards!
_ = self.navigationController?.popViewController(animated: true)
let previousViewController = self.navigationController?.viewControllers.last as! PreviousViewController
previousViewController.PropertyOrMethod
I came across this while looking for a way to do it. Since I use Storyboards more often, I found that I can get the array of controllers in the navigation stack, get the one just before the current one that's on top, check to see if it's my delegate, and if so, cast it as the delegate, set my methods, then pop myself from the stack. Although the code is in ObjC, it should be easily translatable to swift:
// we need to get the previous view controller
NSArray *array = self.navigationController.viewControllers;
if ( array.count > 1) {
UIViewController *controller = [array objectAtIndex:(array.count - 2)];
if ( [controller conformsToProtocol:#protocol(GenreSelectionDelegate)]) {
id<GenreSelectionDelegate> genreDelegate = (id<GenreSelectionDelegate>)controller;
[genreDelegate setGenre:_selectedGenre];
}
[self.navigationController popViewControllerAnimated:YES];
}
Expanding upon the answer by Abdul Baseer Khan:
For cases where the current view controller may have been loaded by different types of previous view controller, we can use the safer as? call instead of as!, which will return nil if the controller is not what we were looking for:
let previousVC = self.navigationController?.viewControllers.last as? AnExampleController
previousVC?.doSomething()
Although, you would need to repeat that for each different view controller that could load the current view controller.
So, you may want to, instead, implement a protocol to be assigned to all the possible previous view controllers:
protocol PreviousController: UIViewController {
func doSomething()
}
class AnExampleController: UIViewController, PreviousController {
// ...
func doSomething() {}
}
class AnotherController: UIViewController, PreviousController {
// ...
func doSomething() {}
}
class CurrentController: UIViewController {
// ...
func goBack() {
let previousVC = self.navigationController?.viewControllers.last as? PreviousController
previousVC?.doSomething()
}
}