Unwind segues with programmatically created view controllers - ios

I have a view controller (PhotoViewController) which has a child view controller (CameraViewController). In CameraViewController, there is a button that sets off a chain of segueing through other programmatically created view controllers. On the last of these view controllers, I want to unwind to the original PhotoViewController. All examples I have found require you to have view controllers in the storyboard, which I don't have. How can I do this?

You have not understood what an unwind segue is. It is merely a way of reversing the calls that created the current view controller and got it into the view controller hierarchy, in the special case where you want to trigger this through a segue in a storyboard.
For example, if you (or the storyboard) called pushViewController (for a pushed view controller), an unwind segue is just a way of calling popViewController.
Or, if you called (or the storyboard) called present (for a modally presented view controller), an unwind segue is just a way of calling dismiss.
If you don't have your view controllers in a storyboard, you don't need an unwind segue; you just do one of those two things, directly, in code.
Remember, we all got along for years just fine without unwind segues. In fact, we all got along for years without storyboards! And so can you.

If your original PhotoViewController is created on a storyboard and you want to segue back to it from a programmatically made VC you have present it rather than unwinding because unwindSegues are for storyboards only.
To present your PhotoViewController here is one of the ways to do so.
func presentPhotoViewController() {
let storyboard = UIStoryboard(name: "YourStoryBoardName", bundle: nil)
if let photoViewController = storyboard.instantiateViewController(withIdentifier: "PhotoViewControllerUniqueId") as? PhotoViewController {
// Pass any data you have (Optional)
self.present(photoViewController, animated: true, completion: nil)
// If your PhotoViewController is embeded in a navigation Controller do the following.
//let navController = UINavigationController(rootViewController: photoViewController)
//self.present(navController, animated: true, completion: nil)
}
}

Related

Swift cancel button to different controllers

I'm coding a simple app with swift and I'm stuck at the following point, I have two Controllers that lead to another one, and when I click on the cancel button, it always lead to the root Controller, no matter from where I come.
I have a first controller (UIViewController), that go to the Navigation Controller of my target Controller (the one from which I would like to go back to the right calling Controller).
I have a second controller (UITableViewController), which go directly to my target Controller.
Here's the code of my Cancel button:
// MARK: - Navigation
#IBAction func lendingCancelButton(_ sender: UIBarButtonItem) {
// Depending on style of presentation (modal or push presentation), this view controller needs to be dismissed in two different ways
let isPresentingInAddLendingMode = presentingViewController is UINavigationController
if isPresentingInAddLendingMode {
dismiss(animated: true, completion: nil)
} else if let owningNavigationController = navigationController {
owningNavigationController.popViewController(animated: true)
} else {
fatalError("the LendingViewController is not inside a navigation controller.")
}
}
If I correctly understood (you could then correct me if I'm wrong, I would learn something), it's testing if the ViewController that's presenting my target ViewController is a NavigationController.
So maybe that, as the second Controller (my UITableViewController) is not going through a NavigationController, so the last one calling my target view with a NavigationController is always the UIViewController.
Don't hesitate to tell me if it's not clear enough (too many times the word "Controller" in my post) or if you need additional code.
Try something like this
if let navigationController = presentingViewController as UINavigationController {
navigationController.popViewController(animated: true)
} else if let viewController = presentingViewController as UIViewController {
dismiss(animated: true, completion: nil)
} else {
fatalError("the LendingViewController is not inside a navigation controller.")
}
If i understood you want to use dismiss when you find a UIViewController and to pop the navigation when you find a UINavigationController right?
Ok so I finally found a way to make it working.
My tableViewController was embedded into a NavigationController. I removed it (since I could do without it, according to my need). From this View Controller, I draw a segue that "Show" my target view.
From my other ViewController (this one is embedded into a NavigationController), I draw a segue put that present modally my target view.
With the code provided in my initial post, it's working.
The only thing I didn't understand is why the NavigationController from my TableViewController was likely to cause it not working properly.

How to avoid memory leaks while presenting / segueing to new View Controllers

In my app I have a MainViewController where user can add, remove and reorder items in CollectionView. Each Collection View Cell initiates segue to a new VC (n-th VC in the image below). From the newly presented vc user can go back to the MainVC or segue to the next (or previous) VC that's also accessible from the MainVCs Collection View.
Since the order of items in Collection View is dynamic I'll have instantiate the next VC and then present it:
let nextVC = storyboard?.instantiateViewController(withIdentifier: "NextVC")
present(nextVC!, animated: true, completion: nil)
My question is (are):
Do I have to worry about a memory leaks if I use unwind segue when
the user taps on goBackToMainVC (I.e. will all previously
instantiated VCs be automatically dismissed?)
If the user decides not to go back to the MainVC, should I dismiss the current VC before presenting a new one? If so, where should I call the dismiss function?
Edit: Additional question:
Would adding
if (presentingViewController?.restorationIdentifier != "MainVC") {
presentingViewController?.dismiss(animated: false, completion: nil)
}
to every VC accessible from the collection view in MainVC solve my problem?
If you are dismissing or unwinding back to the main controller, it would deallocate the loaded view controller(s) that was loaded when presenting. That is, providing there are no strong references to anything to those view controllers.
To verify the view controllers are being deallocated, you can print something to the console when the controllers are dismissed via deinit.
deinit {
print("deinit called")
}
An unwind segue from a Present Modally segue calls dismiss. That is what an unwind segue is. So there is no special memory management associated with an unwind segue.

swift - how to force the app to show a particular view after return from background

Ok, i know that when applicationWillEnterForeground fires from my AppDelegate that I can trigger events. What I would like to do is force the app to show a certain view when It re-appears from the background. The view is a UIViewController called loginViewController and it has a storyboard Id of "initViewController"
My question is, what do I use in this function (applicationWillEnterForground) to make this view load when the app comes into focus again? Thanks.
I've never done this, but you can probably accomplish it by adding the UIViewController to the UIViewController stack, if you just want to add a view controller and show its view (see Case 1) or by replacing the root view controller, if you want to discard the existing view controller stack and use a new one (see Case 2)
Case 1) In the first case you need a reference to the UIViewController that you want to make its parent view controller. You can save this in a static variable somewhere or if you are just planning on showing a temporary view when the app restarts then you can get a reference to the root view controller use it as the parent:
// get a reference to the main storyboard
let mainSB = UIStoryboard(name: "Main", bundle: nil)
// get a reference to the root view controller
if let rootVC = UIApplication.sharedApplication().keyWindow?.rootViewController,
// get a reference to the view controller using identifier
initVC = mainSB.instantiateViewControllerWithIdentifier("initViewController") as? UIViewController {
// present the view controller
rootVC.presentViewController(initVC, animated: false, completion: nil)
}
When you are finished use logic from within the view controller to dismiss it, and your user should be back where they started:
self.dismissViewControllerAnimated(true, completion: nil)
Case 2) You can discard the existing view controller stack and start a new one by replacing the root view controller and building up the stack manually. Present the view controllers in order with animated parameter set to false.
// get a reference to the main storyboard
let mainSB = UIStoryboard(name: "Main", bundle: nil)
// get references to view controllers
if let vc1 = mainSB.instantiateViewControllerWithIdentifier("vc1") as? UIViewController,
vc2 = mainSB.instantiateViewControllerWithIdentifier("vc2") as? UIViewController {
// set root view controller
UIApplication.sharedApplication().keyWindow?.rootViewController = vc1
// build up the view controller stack by adding next vc
vc1.presentViewController(vc2, animated: false, completion: nil)
}
Navigation Controllers
If one of your view controllers is a navigation controller you will need to cast it as such, and then push any view controllers onto your navigation controller. Navigation controllers have their own stack.
if let myNavCon = mainSB.instantiateViewControllerWithIdentifier("nav") as? UINavigationController {
// push view controller onto navigation controller stack
myNavCon.pushViewController(someViewController, animated: false )
}
WARNING
This does not deal with the model of your app at all (only the UI). You will also need to set any data that you would have set in prepareForSegue, etc. An easy system to use when you have VCs you present both programmatically and via storyboard segues is to take the code that would have been in prepare for segue and move it to your own instance method that takes a reference to the child view controller as its parameter. Then you can call it from prepare to segue with the destination view controller or from code before you present the view controller.
None of this code has been tested. It was written directly via the website. It likely contains typos. Please let me know so I can fix any.

How To addSubViews To Storyboard, Then Displaying It Using A Segue

I have a view controller reference to a storyboard of a given identifier. I'm adding a bunch of buttons to it, then trying to display it via a segue.
My problem is that when the segue fires, it creates a difference instance of the view controller with the same segue identifier, and thus it's blank.
What's the best practice to addSubView() to a storyboard, then getting that SAME storyboard object to display?
CLARIFICATION
Here's the flow I'm using:
Central VC -> Create SubVC using centralized Storyboard Object -> Adding SubViews to that SubVC in a factory class -> Queue Segue from SubVC back to the Central VC for segue using its identifier -> [it creates a NEW VC without my additions]
If you're using segues, then the Storyboard creates the destination viewController. If you want to customize the destination viewController, then you do that in prepareForSegue.
You can instantiate a view by code, and pushing in to you navigation controller, it's a clean approach and dont mess the Storyboard with unnecessary segues.
Just instantiate the next view (you must first give this view an StoryBoard ID), call it by code, and push it in the navigation controller.
Objective-C
UIStoryboard* storyboard = [UIStoryboard storyboardWithName:#"storyBoard_Name" bundle:nil];
UIViewController* controller = [storyboard instantiateViewControllerWithIdentifier:#"ViewController_ID"];
[self.navigationController pushViewController:viewControllerName animated:YES];
Swift
let storyboard = UIStoryboard(name: "storyBoard_Name", bundle: nil)
let vc = storyboard.instantiateViewControllerWithIdentifier("ViewController_ID") as! UIViewController
self.presentViewController(vc, animated: true, completion: nil)

UINavigationController Storyboard Hopping

I would like to know what code is required to traverse the storyboard from a UIViewController located at index N of a UINavigationController which is embedded in a UITabBarController, to a similarly embedded UIViewController.
I would also like all UIViewControllers to be popped in the source UINavigationController
Direct segues (as shown in red) do not fit my use case.
Swift please.
You can pop to the root view controller then change the selected index of the index of the tab bar controller then push whatever view controllers you need on the other navigation controller. For example:
let tabBarController = self.tabBarController;
let indexZeroNavController:UINavigationController = self.tabBarController?.viewControllers![0] as! UINavigationController
self.navigationController?.popToRootViewControllerAnimated(true)
tabBarController?.selectedIndex = 0
let newViewController = self.storyboard?.instantiateViewControllerWithIdentifier("New View Controller")
let otherNewViewController = self.storyboard?.instantiateViewControllerWithIdentifier("Other New View Controller")
indexZeroNavController.pushViewController(newViewController!, animated: true)
indexZeroNavController.pushViewController(otherNewViewController!, animated: true)
Beyowulf's approach used to be valid, but things have changed. In the viewController you wish to pop to, define an "unwind segue". example Once it's defined, you can drag from a button to "exit" and select that unwind segue.
The way unwind segues work has been completely reworked in xcode 7, so you don't have to worry too much about the view controller stack.

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