I have a UIStoryboardSegue subclass for replacing current view controller with next view controller.
As we have a Animates property in interface editor, I want to access this property in the subclass.
My code is following:
class ReplaceSegue: UIStoryboardSegue {
override func perform() {
var viewControllers = source.navigationController?.viewControllers.dropLast() ?? []
viewControllers.append(destination)
source.navigationController?.setViewControllers(viewControllers.map {$0}, animated: true) // I dont want this `true` to be hardcoded
}
}
As per comments in UIStoryBoardSegue class
The segue runtime will call +[UIView setAnimationsAreEnabled:] prior
to invoking this method, based on the value of the Animates checkbox
in the Properties Inspector for the segue.
So obviously you can read the value of animate check box by using
UIView.areAnimationsEnabled
So in my custom segue
class MySegue: UIStoryboardSegue {
override func perform() {
debugPrint(UIView.areAnimationsEnabled)
}
}
This prints false if animate checkbox is unchecked or true if it is checked :)
So in your case
class ReplaceSegue: UIStoryboardSegue {
override func perform() {
var viewControllers = source.navigationController?.viewControllers.dropLast() ?? []
viewControllers.append(destination)
source.navigationController?.setViewControllers(viewControllers.map {$0}, animated: UIView.areAnimationsEnabled)
}
}
I hope whats happening is already clear, incase you still have doubt, here is the explanation, iOS checks the animates checkbox value and uses it to set whether animations are enabled or not by calling setAnimationsAreEnabled with the value of animates check box in interface prior to calling perform() method.
So when the control reaches inside perform you can be assured that iOS has already read the value of animates check box and used it to set setAnimationsAreEnabled all you have to do now is to ask areAnimationsEnabled to get the value of animates check box.
So that should provide you the value of animates checkbox :)
Hope it helps :)
You shouldn't need a UIStoryboardSegue subclass for this. The docs state "You can subclass UIStoryboardSegue in situations where you want to provide a custom transition between view controllers". This means that a replacement without without any animation isn't a custom transition, thus shouldn't use a segue subclass.
The correct way to do replacement is to use a Show Detail (e.g. Replace) segue and inside the parent view controller that is managing the child view controllers implement the method showDetailViewController and replace the children, e.g.
#implementation DetailNavigationController
- (void)showDetailViewController:(UIViewController *)vc sender:(id)sender{
[self setViewControllers:#[vc] animated:NO];
}
If you didn't know, the Show Detail segue (after magically instantiating the destination view controller) has a perform method that just calls showDetailViewController on self, and the base UIViewController implementation searches up the view controller hierarchy looking for one that overrides showDetailViewController, so you can intercept it and perform your custom code, before say it goes up to another parent that might implement it also like a split view.
Related
I'm having the hardest time implementing a presentation of a drawer sliding partway up on the screen on iPhone.
EDIT: I've discovered that iOS is not respecting the .custom modalTransitionStyle I've set in the Segue. If I set that explicitly in prepareForSegue:, then it calls my delegate to get the UIPresentationController.
I have a custom Segue that is also a UIViewControllerTransitioningDelegate. In the perform() method, I set the destination transitioningDelegate to self:
self.destination.transitioningDelegate = self
and I either call super.perform() (if it’s a Present Modal or Present as Popover Segue), or self.source.present(self.destination, animated: true) (if it’s a Custom Segue, because calling super.perform() throws an exception).
The perform() and animationController(…) methods get called, but never presentationController(forPresented…).
Initially I tried making the Segue in the Storyboard "Present Modally" with my custom Segue class specified, but that kept removing the presenting view controller. I tried "Present as Popover," and I swear it worked once, in that it didn't remove the presenting view controller, but then on subsequent attempts it still did.
So I made it "Custom," and perform() is still being called with a _UIFullscreenPresentationController pre-set on the destination view controller, and my presentationController(forPresented…) method is never called.
Other solutions dealing with this issue always hinge on some mis-written signature for the method. This is mine, verbatim:
public func presentationController(forPresented presented: UIViewController, presenting: UIViewController?, source: UIViewController) -> UIPresentationController?
I've spent the last four days trying to figure out “proper” custom transitions, and it doesn't help that things don’t seem to behave as advertised. What am I missing?
Instead of using a custom presentation segue, you could use a Container View for your drawer. This way, you can use a UIViewController for your Drawer content, while avoiding the issue with the custom segue.
You achieve this in two steps:
First pull a Container View into your main view controller and layout it properly. The storyboard would look like this: (You can see you have two view controllers. One for the main view and one for the drawer)
Second, you create an action that animates the drawer in and out as needed. One simple example could look like this:
#IBAction func toggleDrawer(_ sender: Any) {
let newHeight: CGFloat
if drawerHeightConstraint.constant > 0 {
newHeight = 0
} else {
newHeight = 200
}
UIView.animate(withDuration: 1) {
self.drawerHeightConstraint.constant = newHeight
self.view.layoutIfNeeded()
}
}
Here, I simply change the height constraint of the drawer, to slide it in and out. Of course you could do something more fancy :)
You can find a demo project here.
I'm new to swift and am trying to write an app with it.
I have a UIViewController that I am transitioning to. I have designed the UI in interface builder and I intend to use segues to manage the transition. However, the view controller relies on data that is passed into the view controller from the previous view controller.
If I have properties on my view controller then I will need to redefine my init method. But I wouldn't normally call the init method; it would be called for me before prepareForSegue. So I see a few possible solutions:
Make my variables optional (so I can pass them in prepareForSegue
and update the view then).
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
let viewController: EventViewController = segue.destinationViewController as! EventViewController
viewController.event = self.event
}
Manually init my view controller and present it programmatically instead.
???
Is there a third option? If not, which of the previously mentioned 2 is better practice?
There is two possible options as you mentioned:
The first one is the easiest which is to pass the data in prepareForSegue. which you don't have to care about dismissing the controller or keeping a track of inner view controllers,because storyboard will take care of it.
The second way is to set a Storyboard ID in storyboard,for the controller you need to present programmatically, which need more things to handle, like to dismiss the controller or keep track of inner presented controllers.
let nextViewControllerName = storyboard?.instantiateViewControllerWithIdentifier("Storyboard ID") as! nextViewControllerName
nextViewControllerName.event = self.event
self.presentViewController(nextViewControllerName, animated: true, completion: nil).
At the end they does the same purpose.
Note: You should always pass the data before presenting the controller.
I'm learning Swift and I'm studying the delegation pattern.
I think I understand exactly what is delegation and how it works, but I have a question.
I have a situation where Controller A is the delegate for Controller B.
In controller B I define a delegate protocol.
In controller B I set a variable delegate (optional)
In controller B I send message when something happens to the delegate
Controller A must adopt method of my protocol to become a delegate
I cannot understand if every delegate controller (in this case A) listens for messages sent by controller B or If I have to tell to controller B that A is now his delegate.
I notice that someone use this code (in controller A)
override func prepareForSegue(segue: UIStoryboardSegue, sender: AnyObject?) {
if segue.identifier == "Example" {
let navigationController = segue.destinationViewController as UINavigationController
let controller = navigationController.topViewController as AddItemViewController
controller.delegate = self
}
}
Is this the only way to tell a delegator who is his delegate?
I believe, you need to tell a deligator who is its delegate upon creation of that it. Now, the delegator can be created programatically or through storyboard. So, based on that you have two options, you can tell it who is its delegator programatically like you showed in the code or from IB.
The key here is upon creation. Let's me explain myself. Take the case of a UIView. Say, you want a Custom UIView object(CustomView). So, you drag and drop a UIView in your View Controller and in the identity inspector, you assign its class as of your CustomView's class. So, basically, as soon as the controller is created, your custom view will also be created. Now, you can either say it that the View Controller in which it is created is its delegate or You can go to the IB and connect the view's delegate to the View Controller.
Now, let's assume that you wanted the custom view to be created in your ViewController programatically. In that case, you would probably call the -initWithFrame: method to create the view and upon creation you tell that delegator that who is its delegate like-
myCustomView.delegate = self;
same goes with a View Controller.
controller.delegate = self;
So, basically to tell a delegator who is its delegate, you first need that delegator to be created. At least, that's what I think.
I think one of the best example of delegation is UITableView.
Whenever you want the control of various properties of a tableView e.g. rowHeight etc, you set your controller to be the delegate of your tableview. To set the delegate of your tableView you need to have tableView created obviously as pointed out by #natasha.
So in your case, you can set delegate of your delegator when you create it or when you find a need for the controller to be delegate of your delegator but you definitely need your delegator to be present to set its property.
You can set your controller as delegate at any time when you require control.
I'm sure you want your UIViewController to act like described, but here is a simpler example how to use the delegation pattern with custom classes:
protocol ControllerBDelegate: class {
func somethingHappendInControllerB(value: String)
/* not optional here and passes a value from B to A*/
/* forces you to implement the function */
}
class ControllerB {
var delegate: ControllerBDelegate?
private func someFunctionThatDoSomethingWhenThisControllerIsAlive() {
/* did some magic here and now I want to tell it to my delegate */
self.delegate?.somethingHappendInControllerB(value: "hey there, I'm a magician")
}
func doSomething() {
/* do something here */
self.someFunctionThatDoSomethingWhenThisControllerIsAlive()
/* call the function so the magic can really happen in this example */
}
}
class ControllerA: ControllerBDelegate {
let controllerB = ControllerB()
init() {
self.controllerB.delegate = self /* lets say we add here our delegate*/
self.controllerB.doSomething() /* tell your controller B to do something */
}
func somethingHappendInControllerB(value: String) {
print(value) /* should print "hey there, I'm a magician" */
}
}
I wrote the code from my mind and not testet it yet, but you should get the idea how to use such a pattern.
I have some problems to use subclasses in Swift, hope someone can help me.
What I have
Two view controllers:
VC1 with just some UIButtons
EffectVC that do some animation depending on the button pressed on VC1
import UIKit
protocol viewAnimation {
func initialStateSet()
func finalStateSet()
}
class EffectVC: UIViewController {
#IBOutlet weak var mainImage: UIImageView!
override func viewDidLoad() {
super.viewDidLoad()
self.initialStateSet()
}
override func viewDidAppear(animated: Bool) {
self.finalStateSet()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
func initialStateSet() {
}
func finalStateSet() {
}
}
class GrowingEffect : EffectVC, viewAnimation {
override func initialStateSet() {
// some stuff
}
override func finalStateSet() {
// other stuff
}
}
The problem
Maybe a simple question but I can't do what I want in Swift: I need to set a subclass according to the button that is pressed.
In other words I need to present subclassed view controller from my VC1 according to which button is pressed on VC1.
If I press the first button for example I want to show the VC 2 with the class GrowingEffect for use some custom stuff (this stuff must change according to the selected button).
What I tried
use IBAction for create my subclassed VC2 and show it
let storyboard = UIStoryboard(name: "Main", bundle: nil)
let destinationViewController : UIViewController = storyboard.instantiateViewControllerWithIdentifier("EffectVC") as! GrowingEffect
self.presentViewController(destinationViewController, animated: true, completion: nil)
but I got
Could not cast value of type 'ViewAnimationDemo.EffectVC'
(0x109948570) to 'ViewAnimationDemo.GrowingEffect' (0x109948650).
use PrepareForSegue
but I can't set any subclass
What I really want to do
I know there are some other solution, like not using storyboard, but now I describe exactly what I want to do, hoping this is possibile:
have only one view controller in IB (EffectVC) associate with the class EffectVC. The class EffectVC has some subclasses like GrowingEffect.
In my code I want to instantiate the view controller EffectVC with the subclass that I need: for example instantiate the view controller in IB EffectVC with the class GrowingEffect.
I know that if I have one view controller for every subclass of EffectVC I can do what I want but I don't want so many view controller in IB because they are equal, the only things that I want to change are 2 methods.
I think there are some things mixed up in your setup. You should have 2 view controllers, each set up in its file, and each present in the storyboard with its identifier. It is ok if GrowingEffect inherits from EffectVC.
What you currently do with as! GrowingEffect is actually trying to cast the UIViewController instance you get from calling instantiateViewControllerWithIdentifier("EffectVC") to GrowingEffect. This will not work, because it is of type EffectVC.
Rather, you need to call instantiateViewControllerWithIdentifier("EffectVC") if button X is pressed, and instantiateViewControllerWithIdentifier("GrowingEffect") if button Y is pressed.
EDIT
If you use storyboard, you have to instantiate view controllers using instantiateViewControllerWithIdentifier. But you can only get an instance of GrowingEffect, if it is present on the storyboard.
It is not possible to "cast" an instance of EffectVC to GrowingEffect once created.
So, you have two possibilities here:
Use storyboard and put both view controllers on it. Use instantiateViewControllerWithIdentifier to instantiate the view controller you need, depending on the button pressed.
Do not use storyboard. Then you can create the needed view controller manually and use your UINavigationController's pushViewController method to present it.
You can't cast from parent class to child class, parent class just doesn't have the capacity to know what the child is doing. You can however cast from a child to parent, so you would want to set your view controller as GrowingEffect, then cast it to Effect, but again there is no strong suit to doing this either unless some method needs the parent class and you are using the child class. It looks like you need a redesign of how you want your view controllers laid out. Now I am assuming you have 2 children, lets call GrowingEffect and ShrinkingEffect. In your designer, you set your 1 to GrowingEffect and the other to ShrinkingEffect and make sure they have unique identifiers. Then you can use your view to present an Effect, and pass in either of those objects.
A user is in a view controller which calls a modal. When self.dismissViewController is called on the modal, a function needs to be run on the initial view controller. This function also requires a variable passed from the modal.
This modal can be displayed from a number of view controllers, so the function cannot be directly called in a viewDidDisappear on the modal view.
How can this be accomplished in swift?
How about delegate?
Or you can make a ViewController like this:
typealias Action = (x: AnyObject) -> () // replace AnyObject to what you need
class ViewController: UIViewController {
func modalAction() -> Action {
return { [unowned self] x in
// the x is what you want to passed by the modal viewcontroller
// now you got it
}
}
}
And in modal:
class ModalViewController: UIViewController {
var callbackAction: Action?
override func viewDidDisappear(_ animated: Bool) {
let x = … // the x is what you pass to ViewController
callbackAction?(x)
}
}
Of course, when you show ModalViewController need to set callbackAction like this modal.callbackAction = modalAction() in ViewController
The answer supplied and chosen by the question asker (Michael Voccola) didn't work for me, so I wanted to supply another answer option. His answer didn't work for me because viewDidAppear does not appear to run when I dismiss the modal view.
I have a table and a modal VC that appears and takes some table input. I had no trouble sending the initial VC the modal's new variable info. However, I was having trouble getting the table to automatically run a tableView.reloadData function upon dismissing the modal view.
The answer that worked for me was in the comments above:
You likely want to do this using an unwind segue on the modal, that
way you can set up a function on the parent that gets called when it
unwinds. stackoverflow.com/questions/12561735/… – porglezomp Dec 15
'14 at 3:41
And if you're only unwinding one step (VC2 to VC1), you only need a snippet of the given answer:
Step 1: Insert method in VC1 code
When you perform an unwind segue, you need to specify an action, which
is an action method of the view controller you want to unwind to:
#IBAction func unwindToThisViewController(segue: UIStoryboardSegue) {
//Insert function to be run upon dismiss of VC2
}
Step 2: In storyboard, in the presented VC2, drag from the button to the exit icon and select "unwindToThisViewController"
After the action method has been added, you can define the unwind
segue in the storyboard by control-dragging to the Exit icon.
And that's it. Those two steps worked for me. Now when my modal view is dismissed, my table updates. Just figured I'd add this, in case anyone else's issue wasn't solved by the chosen answer.
I was able to achieve the desired result by setting a Global Variable as a boolean value from the modal view controller. The variable is initiated and made available from a struct in a separate class.
When the modal is dismissed, the viewDidAppear method on the initial view controller responds accordingly to the value of the global variable and, if needed, flips the value on the global variable.
I am not sure if this is the most efficient way from a performance perspective, but it works perfectly in my scenario.