I am new to Swift programming. I am stuck in one scenario.
When my app loads, the first screen gets in ViewController1 user's latitude and longitude and then gets the data from a backend API and loads the data in a table view controller. This code of getting user's location and loading table view controller is in ViewDidLoad method. In this ViewController1, I have a button when tapped, I am presenting a view controller (Which is embedded in a navigation controller) modally. The following lines of code I am using to present this new ViewController (ViewController2).
let VC2 = self.storyboard?.instantiateViewControllerWithIdentifier("NewVC2") as! NewVC2
let navController = UINavigationController(rootViewController: VC2)
VC2.delegate = self
self.presentViewController(navController, animated: true, completion: nil)
When I close the ViewController2 by saying self.dismissViewController, it closes and when the control comes back to ViewController1, ViewDidLoad is executed again and all the code of invoking backend API and getting user's location is getting invoked.
So, for passing data back from ViewController2 on dismissing it, I used the delegate pattern. Created a protocol and defined a method in this protocol.
protocol ViewControllerClosedDelegate {
func isViewControllerClosed(closed: Bool);
}
defined the object of delegate in ViewController2.
var delegate: ViewControllerClosedDelegate! = nil
and added the following code while dismissing ViewController2.
delegate.isViewControllerClosed(true)
self.dismissViewControllerAnimated(true, completion: nil)
made the ViewController1 to implement this ViewControllerClosedDelegate and added the following function.
func isViewControllerClosed(closed: Bool) {
self.isFromClosedVC = closed
print(isFromClosedVC)
}
isFromClosedVC is a global variable defined ViewController1.
the value is printing correctly (true in this case) as being passed from ViewController2 when it is dismissed but when I try to print this in ViewDidLoad, it is being printed as false.
I thought of getting this value from ViewController2, and if it is true, not to execute the code to get users location and data from backend API.
Basically, I am trying to get the user's location and getting the data from backend API once and update my table view only on Swipe to refresh.
How do I achieve this? Please help.
Thank you.
Raj
Related
I am trying to use InAppSettingsKit from my Swift app (via Swift package dependency to version 3.3.3), and I would like to be able to use the settingsViewControllerDidEnd delegate callback to determine when the user has dismissed the settings dialog, so that I can check for certain conditions that may require additional actions on the user's part.
The Done button was showing up if I pushed the view controller onto a navigation controller, but the code indicates that this method will not fire the Done button delegate callback, so I have been trying to use the present method to show the view controller.
Here is the code that I am using to instantiate and present the settings view controller:
func authenticationSettings(alert: UIAlertAction!) {
let viewController = IASKAppSettingsViewController()
viewController.delegate = self
self.present(viewController, animated: true, completion: nil)
}
And here is what I get, notice no Done button:
I have tried this card method of presenting, and also the full screen method, with no avail.
I tried stepping into the Objective-C code and and from what I could tell, the UIBarButtonItem navigation item was being created and added. Anyone have any ideas on what to try next?
As you may have noticed in the source code, UIBarButtonItem gets added on navigationItem. This item is used only if view controller is part of a navigation controller stack
When you're presenting a new view controller modally it doesn't have a navigation controller in the stack, so to make it work you need to wrap your controller with a UINavigationController:
func authenticationSettings(alert: UIAlertAction!) {
let viewController = IASKAppSettingsViewController()
viewController.delegate = self
let navigationController = UINavigationController(rootViewController: viewController)
self.present(navigationController, animated: true, completion: nil)
}
Following Apple's documentation for adding and editing information Apple guide here I have a Viewcontroller with a tableview. The tableview contains a header with a "Add new" Button. If a table row is selected the detailViewController is pushed onto the stack. The detailViewController is also embedded in a UINavigationController, as in Apple's docs. If "Add new" is pressed, another segue is performed which presents the UINavigationController modally, which in turns shows the detailViewController. This works fine and the animation clearly shows a modally presented ViewController.
The detailViewController contains a Cancel Button in the NavigationBar. If it is pressed the following code is run:
#IBAction func cancel(_ sender: UIBarButtonItem) {
// Depending on style of presentation (modal or push presentation), this view controller needs to be dismissed in two different ways.
var isPresentingInAddActionMode = false
if let presentingVC = self.presentingViewController{
isPresentingInAddActionMode = presentingVC is UINavigationController
}
streekgidsModel.undoManager.endUndoGrouping()
print("undo grouping ended and undone")
streekgidsModel.undoManager.undo()
if isPresentingInAddActionMode {
dismiss(animated: true, completion: nil)
}
else if let owningNavigationController = navigationController{
owningNavigationController.popViewController(animated: true)
}
else {
fatalError("The MealViewController is not inside a navigation controller.")
}
}
The first if-statement checks if the property presentingViewController is present, and if so if it is of type UINavigationController. If so, the viewController is presented modally and should be dismissed. If not it is pushed onto the stack and the owningNavigationController should pop the detailViewController.
Running this code does not work as described by Apple. The check on the presentingViewController shows it is present, but the type check gives back "invalid". This is treated as false. The test on the owningNavigationController succeeds (I think it should fail) and the popViewController is executed. As there was no push, the view controller is not popped or dismissed and is still visible. A second press on Cancel executes the func cancel again, which results in an error as there is no longer a group started in the undo manager.
Baffling thing is that I have the same code in another viewcontroller, with similar UIViewTable and navigation and it works fine.
So to frame the question: why does this not work the way Apple describes it, why does my other view controller work as it is supposed to? Any input is appreciated.
BTW, the fatal error text is straight from the docs so the naming is not relevant and it is never executed.
I would start with checking who is presenter.
According to Apple docs on this:
When you present a view controller modally (either explicitly or implicitly) using the present(_:animated:completion:) method, the view controller that was presented has this property set to the view controller that presented it. If the view controller was not presented modally, but one of its ancestors was, this property contains the view controller that presented the ancestor. If neither the current view controller or any of its ancestors were presented modally, the value in this property is nil.
If the docs are correct then your presenter should be your "Viewcontroller with a tableview" which, I guess, is not UINavigationController. If that is the case then you should understand why your code fails.
It depends on your context of course, but I would just simplify a check this way:
var isPresentingInAddActionMode = self.presentingViewController != nil
... // your other code
if isPresentingInAddActionMode {
dismiss(animated: true, completion: nil)
}
else if let owningNavigationController = navigationController{
owningNavigationController.popViewController(animated: true)
}
If I understood your question and intent correctly then it doesn't matter for you who (which class) presented your detailVC and you care only about how your detailVC was presented - either pushed in navigation view controller or presented modally. I think just by checking presentingViewController property you can get that information.
I am using Map Kit View. mapViewWillStartLoadingMap method called when I navigate MapViewController first time. Then I go back previous controller and again navigate MapViewController , mapViewWillStartLoadingMap not called. Where is my mistake ?
I am using this method go to previous controller from MapViewController
dismissViewControllerAnimated(true, completion: nil)
Check that your ViewController containing the map is being deInitialised.
Add this to your VC and set a breakpoint on it.
deinit {
}
If its not that, check the delegate for the map view is set correctly when your map VC is on active.
I'm trying to achieve passing of data using segue, but without displaying the screen. There are two view controllers in my project and I will name them FirstViewController and SecondViewController.
On FirstViewController, I am using Show Adaptive Segue to pass data using performSegueWithIdentifier. The prepareForSegue method will be called, and recognising the identifier I've set to display SecondViewController.
However, the problem is I do not want to display SecondViewController. There are other things that my users may want to do before heading for SecondViewController.
I'm new to iOS programming, and I only know passing of data with segue. Please do share with me if there are methods to pass data apart from segue.
EDIT: To further elaborate my question. I'm working with TabBarController, and both View Controllers are accessible on the Tab bar. So when I am on SecondViewController with some data already "segue-ed" over from FirstViewController, I can head back to FirstViewController to add more data. At SecondViewController with UIRefreshControl I need the updated data.
If you do the segue in code you can do what you want in a following way
1) Instantiate view controller from the story board
let storyboard: UIStoryboard = UIStoryboard(name: "SecondViewController", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier("set_it_in_IB") as! SecondViewController
2) Set the properties you need to set as the view controller is already instantiated
vc.someProperty = "asd"
3) Segue!
viewController.presentViewController(viewControllerToPresent: UIViewController, animated: Bool, completion: (() -> Void)?)
Hope that helps!
From your user's perspective, they would not know whether the data is being updated before they segue or not, so it is probably fine to just pass the data with the prepareFoSegue function.
Otherwise, you could try setting a notification to the viewDidLoad on your FirstViewControllerand SecondViewController by
NSNotificationCenter.defaultCenter().addObserver(self, selector: nil, name: updateSecondVCNotification, object: nil)
and posting the notification from the FirstViewController whenever the data needs to be updated using the
NSNotificationCenter.defaultCenter().postNotificationName(updateSecondVCNotification, object: self)
Then on second view controller set the the selector of the addObserver to a string of the name of whatever function you want it to do like "reloadNewData"
func reloadNewData() {
tableView.reloadData()
}
Does this help? Don't forget to set the updateSecondVCNotification as a global string constant at the top of your FirstViewController. Learn more about NSNotificationCenter at https://www.andrewcbancroft.com/2014/10/08/fundamentals-of-nsnotificationcenter-in-swift/
Woo! Notifications! ＼(＾▽＾)／
I'm not sure if that would work for you, but you could simply keep the data in memory of your FirstViewController for the time during which the user is still interacting and giving feedback and once it's done, send all the data to the SecondViewController through the segue.
I'm presenting a modal view controller using a custom transition (by setting its modelPresentationStyle to UIModalPresentationCustom, providing a transitioning delegate, and UIViewControllerAnimatedTransitioning object).
In the presented view controller, I have an unwind segue hooked up to a button. The segue fires just fine; the IBAction method in the presenting view controller is called, and so is prepareForSegue in the presented view controller. However, the presented view controller is not dismissed, and the appropriate transitioning delegate method (animationControllerForDismissedController:) is not called.
If, however, I set the presented view controller's modalPresentationStyle to UIModalPresentationFullScreen (the default), the view controller is dismissed properly (this breaks my custom transition, though).
I'm at a complete loss at what to do here. I've looked through Apple's documentation, and didn't notice anything saying that one had to do special things with unwind segues when dealing with custom transitions.
I'm aware that I could call dismissViewControllerAnimated:completion: in the IBAction method of the presenting view controller, but I'd rather use that as a last resort, and get the unwind segue working the way it should (or at least know why it's not working :) ).
Any help would be much appreciated,
Thanks in advance
It seems that if you use UIModalPresentationCustom to present the controller with a custom transition manager, you also need to use a custom transition manager to dismiss it (which makes sense I guess, since you can do all kinds of weird stuff in the animator object and UIKit can't be sure that just dismissing the screen as usual will completely restore the original state - I just wish it told you that explicitly...).
Here's what I've done to fix this in my app:
override segueForUnwindingToViewController in the parent view controller (the one to which you're moving after the dismiss animation) and return an instance of your UIStoryboardSegue, either the one you've used for the original transition or a new separate class
if the unwind segue's target view controller is in a navigation hierarchy, then you need to override that method in the navigation controller instead
in the perform method call dismissViewControllerAnimated
the presented view controller needs to still hold a valid reference to the transitioning delegate, or you'll get an EXC_BAD_ACCESS (see DismissViewControllerAnimated EXC_Bad_ACCESS on true) - so either make it keep the delegate as a strong reference as described in that thread, or assign a new one before calling dismissViewControllerAnimated (it's possible that changing modelPresentationStyle to e.g. full screen before dismissing would work too, but I haven't tried that)
if the dismiss animation needs to do any non-standard things (mine luckily didn't), override animationControllerForDismissedController in the transition manager object and return a proper animator
if the target view controller is in a navigation hierarchy, then you also need to manually pop the navigation stack to the target controller before dismissing the presented screen (i.e. target.navigationController!.popToViewController(target, animated: false))
Complete code sample:
// custom navigation controller
override func segueForUnwindingToViewController(toViewController: UIViewController,
fromViewController: UIViewController,
identifier: String?) -> UIStoryboardSegue {
return CustomSegue(
identifier: identifier,
source: fromViewController,
destination: toViewController
)
}
// presented VC
var customTransitionManager: UIViewControllerTransitioningDelegate?
// custom segue
override func perform() {
let source = sourceViewController as! UIViewController
if let target = destinationViewController as? PresentedViewController {
let transitionManager = TransitionManager()
target.modalPresentationStyle = .Custom
target.customTransitionManager = transitionManager
target.transitioningDelegate = transitionManager
source.presentViewController(target, animated: true, completion: nil)
} else if let target = destinationViewController as? WelcomeViewController {
target.navigationController!.popToViewController(target, animated: false)
target.dismissViewControllerAnimated(true, completion: nil)
} else {
NSLog("Error: segue executed with unexpected view controllers")
}
}
I also met this problem when I need to pass data back from the modalpresented view.
I wandering around Google and here for a couple of hours but I couldn't find an answer that is easy to understand for me. But I did get some hint and here's a work around.
It seems that because it has to pass data back, and the dismissing process from the automatic Unwind is prior before the data passing which prevented the ViewController being dismissed. So I think that I have to manually dismiss it once one more time.
I got some luck here. I didn't notice that it was a child viewcontroller. I just configured it from the storyboard.
And then in the Unwind function, I added to lines to remove the child viewcontroller and the child view. I have no code in the sourceViewController.
Swift 4.1
#IBAction func unwindToVC(sender :UIStoryboardSegue){
if let source = sender.source as? CoreLocationVC{
if source.pinnedCity != nil{
clCity = source.pinnedCity
}
if source.pinnedCountry != nil {
clCountry = source.pinnedCountry
}
if source.pinnedTimeZone != nil {
clTimeZone = source.pinnedTimeZone
}
if source.pinnedLocation != nil {
clLocation = source.pinnedLocation
}
// I added 2 lines here and it just worked
source.view.removeFromSuperview()
source.removeFromParentViewController()
}