My app has a navigation controller where the first view controller is a login screen and all other screens are pushed on top.
I would like to unwind to the login screen whenever any http request to the backend returns a 401 error.
What I had in mind was to add an extension to the ViewController class with something like this:
extension UIViewController {
func unwindToLoginScreen() {
performSegue(withIdentifier: loginScreen)
}
}
And the segue would be an unwind segue. Then, whenever the request fails I call the view controller's unwindToLoginScreen method.
However, the problem with this approach is that I would have to remember to create said unwind segues on the storyboard for all new view controllers that I added to the project.
So far I think the ideal plan would be to be able to create the unwind segue programatically instead of using the storyboard. So, my unwindToLoginScreen() extension method would work in any new view controller by default. Something like:
extension UIViewController {
func unwindToLoginScreen() {
let segue = UnwindSegue(identifier: "blablah", segue: LoginViewController.unwindToLoginViewController)
segue.perform()
}
}
Is it possible to do something like this?
You can't create segues in code, but you can pop to the root of the UINavigationController's stack:
func returnToLoginScreen() {
self.navigationController?.popToRootViewController(animated: true)
}
If you want to pop to a viewController that isn't the root, you can find it in the array of viewController's managed by the UINavigationController and then call popToViewController:
// pop to second viewController in the stack
self.navigationController?.popToViewController(self.navigationController!.viewControllers[1], animated: true)
... or search for the ViewController by type:
if let loginVC = self.navigationController?.viewControllers.first(where: { $0 is LoginViewController }) {
self.navigationController?.popToViewController(loginVC, animated: true)
}
Related
in my iOS app the user navigates using a navigation controller.
The user navigates using different UITableViewController.
UIViewController - UITableViewController - UITableViewController
After the user has selected an item in the "last" UITableViewController I am using the following call to return to the root view controller:
DispatchQueue.main.async { self.navigationController?.popToRootViewController(animated: true) }
How can I send data back to the root controller? Previously I used notifications, but I really dislike this concept. Is there a more elegant way?
Should every single UIViewController on the view-stack implement his own callback which is initialized using the
func prepare(for segue: UIStoryboardSegue, sender: Any?)
method?
How can this be implemented elegantly?
If you are using segues, you could create an unwind segue and use it instead of popToRootViewController. Here you can see how to create an unwind segue.
Otherwise, based on your hierarchy, before popToRootViewController, you could access your view controller like this:
if let rootVC = navigationController?.viewControllers.first as? YourViewControllerClass {
rootVC.someProperty = dataToPass
}
navigationController?.popToRootViewController(animated: true)
I start of with a tableViewController that has a list of names. When the user taps on a name, they are segued to a view controller.
While in that viewController the user may press a button that will take them to another table view Controller.
The layout is like this:
TableViewController(1) -> ViewController -> TableViewController(2)
My question is, how can I pop back to the first TableViewController from the Second TableViewController.
My rootViewController is my signIn View controller so I cannot pop back to root.
You can run this to pop to your rootViewController:
self.navigationController?.popToRootViewController(animated: true)
Update:
Since your rootViewController is not where you want to end up then you can iterate through your controllers and pop to a specific one:
for controller in self.navigationController!.viewControllers {
if controller.isKind(of: TableViewControllerOne.self) {
self.navigationController!.popToViewController(controller, animated: true)
break
}
}
Instead of TableViewControllerOne.self update to your desired controller.
If you're familiar with segues, you can implement an unwind segue. That would give you the added benefit of passing information back to TableViewController(1) if you needed to. To make that work in TableViewController1 you would add some code that looked like:
#IBAction func unwind(fromTableVC2 segue: UIStoryboardSegue) {
if (segue.source is TableVC2) {
if let svc = segue.source as? TableVC2 {
// pass information back
}
}
}
Then in your storyboard you would go to where you have your TableVC2 and drag the yellow VC circle to the exit and choose the function we created above. Name the segue (for this example we'll call it "UnwindToTableVC1"), and then somewhere in TableVC2 add the code:
func setVariableToPassBack () {
// Set up variables you want to pass back
performSegue(withIdentifier: "UnwindToTableVC1", sender: self) }
And that will take you back to your chosen destination with any information you wanted to pass back.
If you don't want to pass anything back, you really just need call the below line in your TableVC2:
performSegue(withIdentifier: "UnwindToTableVC1", sender: self)
I am working in storyboard and also programmatically do some things. First, I have created a viewController controller which is login page (first view) programmatically. But in storyboard I have a NavigationController whose root is ViewController. Everything (methods forgotPassword and loginDidFinish) worked fine, except that ViewController was viewed before controller immediately after launching the app.
So I have changed the root of NavigationController to controller, and after that my functions does not work. I've tried several things like deleting navcontrol in storyboard, etc. You can see my project here: https://github.com/ardulat/SPE
I will provide you a basic example of a Login scenario, hope it can help you with your issue, what I would do first is set right the navigation between ViewControllers like this:
I have two view controllers in my project (LoginViewController.swift and MainViewController.swift):
So in my storyboard I create two ViewControllers, the first one embedded with NavigationController then I set a segue from my first ViewController to my second ViewController:
Then I give a name to the segue I created like so:
And in order to navigate from Login to Main ViewController, I call the performSegue method inside the loginButtonTapped action that is triggered when the login button is touched.
LoginViewController.swift:
class LoginViewController: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
}
#IBAction func loginButtonTapped(_ sender: AnyObject) {
// TODO: validate your login form
performSegue(withIdentifier: "LoginToMain", sender: nil)
}
}
I created a file called "Util.swift" and it has a class "class VC: UIViewController" and has a 2 functions:
Next(segue: String) {
performSegueWithIdentifier(segue, completion: nil)
}
Back() {
dismissViewControllerAnimated(true, completion: nil)
}
So basically, the functions just tell the current viewController to go to the next View or go back to the previous view.
However, in another file, I have an IBAction which is attached to a button and in that action I call the function "Back" in the Util file by doing this:
#IBACTION func ~~~ {
nextVC = Util()
nextVC.back()
}
However, when I click the button, it doesn't do anything.
When I try to connect another button to an action that calls the "next" function in the Util file by doing the same thing and putting in the segue indetifier parameter, it says SIGABRT error: no segue identifier called "xxx".
Can anyone help me? Should I simply use XIB and not use segues?
You have to initialize the UIViewController either with storyBoard or with XIB. If you are doing with factory init() method then it doesn't do anything for you; that means, that is not a viewController which is associated either with storyBoard or XIB. So all you need to do is instantiate the viewController with either options. Before that you need to set an identifier for the viewController to instantiate it.
let storyBoard = UIStoryBoard(name: "MainStoryBoard", bundle: nil)
let vc = storyBoard.instanstiateViewControllerWithIdentifier("YOUR_IDENTIFIER") as! Util
//call your Next method like this
vc.Next(segue:"identifier")
Please refer the document
Apple Doc
In order to use segues, the view controller instance needs to be associated with a Storyboard. In order to be associated with a storyboard, a view controller instance either needs to be the result of a segue or instantiated from a storyboard via instantiateViewControllerWithIdentifier.
When you create an instance of Util via Util() you have a view controller instance that isn't associated with a storyboard and isn't actually presented on screen.
As a result, when you try and perform a segue, you get an error since the segue can't be found.
Also, when you try and dismiss the view controller in back() you are trying to dismiss a view controller that isn't presented.
I am not sure why you want to wrap two fairly simple functions inside next and back, but you can do this using a superclass for all of your view controllers and have this superclass implement your next and back functions:
class MyViewContollerSuperclass: UIViewController {
func next(segue: String) {
self.performSegueWithIdentifier(segue, sender: self)
}
func back() {
self.dismissViewControllerAnimated(true, completion: nil)
}
}
Then you actual view controller would be declared as:
class MyActualViewController: MyViewContollerSuperclass {
#IBACTION func ~~~ {
self.back()
}
}
So, I have Navigation Controller. there are segue from Root View Controller to other View Controller.
When I want to get access to other View Controller I override prepareForSegue method and use destinationViewController property.
But that's not ok for me. All my stuff in prepareForSegue will be execute every time when segue is called, but I don't want it. Secondly, it destroys logic of my code: after performSegueWithIdentifier(actually before) execution jumps to other place in code.
It would be great if I can get access to other View Controller like I did it with Root ViewController - by keyword self, for example.
That's code example to make my question more clearer:
func startWorking() {
/*here we made some stuff for current VC
...
...
*/
//next we go to new View Controller
performSegueWithIdentifier("newVC", sender: nil)
//then all actions that I want to do begin at another method - prepareForSegue
//But I want get access to View Controller that user sees now!
//For example present some view:
let someView = UIView(frame: someFrame)
/*question subject*/.view.addSubview(somView)
}
/question subject/ - is the current ViewController that I have presented by segue and point of my question.
Sergey Gamayunov,
You can always access the top mostViewController in navigation stack using,
let viewCOntroller = self.navigationController?.topViewController
EDIT
I believe if you cant get your logic around the prepareForSegue or self.navigationController?.topViewController you must take a look into your design pattern :)
That being said I understand all you want to do is to access the ViewController after performSegue without using prepareForSegue, you can use this code
func navigationController(navigationController: UINavigationController, didShowViewController viewController: UIViewController, animated: Bool) {
if viewController is YourDestinationViewControllerClass {
print("You have access to viewController loaded do whatever you want")
}
}
The function stated above is a navigation controller delegate :) So you will have to declare your viewController to confirm UINavigationControllerDelegate. like
class ViewController: UIViewController,UINavigationControllerDelegate
and in
override func viewDidLoad() {
super.viewDidLoad()
self.navigationController?.delegate = self
}
Thats it you are good to go :) Happy coding buddy :)