I have a view named AppPurchaseViewController that calls a function from the IAPManagerm class. After my receipt is validated as a in app purchase, I want to perform a segue using the segue id that I set up in my AppPurchaseViewController class. When I try that, Xcode gives me an error that says "AppPurchaseViewController: 0x117e70ae0>) has no segue with identifier". My code is below
case .purchased:
print("Purchased")
self.validateReceipt(completion: {(success) in
if success {
SKPaymentQueue.default().finishTransaction(transaction)
}
else {
}
//here is where I want to perform the segue
AppPurchaseViewController().performSegue(withIdentifier:'open', sender:nil)
})
Can someone point me in the right direction to get this view to load?
At the top of your IAPManager class, you should declare an instance of type AppPurchaseViewController, like so:
var appPurchaseVC: AppPurchaseViewController!
Whenever you declare your IAPManager, assuming it is from within the AppPurchaseViewController class, you should set the IAPManager’s appPurchaseVC value.
var iapManager = IAPManager()
iapManager.appPurchaseVC = self
Then from within your IAPManager, at a later time when you want to perform the segue, call:
appPurchaseVC.performSegue(withIdentifier:'open', sender:nil)
This ensures that you are calling performSegue from the storyboard instance of AppPurchaseViewController. In your current code, you are creating a new instance of AppPurchaseViewController (I.e., not the one in your storyboard) and then calling performSegue. Because this new instance isn’t in our storyboard, it naturally cannot perform a segue to another view controller in the storyboard.
Related
I have a View-Hierarchy like this:
UIViewController (SingleEventViewController)
UIScrollView (EventScrollView)
UIView (contentView)
3xUITableView (SurePeopleTV, MaybePeopleTV, NopePeopleTV (all inherited from the same UITableView)), & all other UI-Elements
The SingleEventViewController stores one Event (passed within the initializer). (All Events are stored in Core-Data).
The three UITableViews are there for displaying the users which are participating (or not or maybe) at the Event. My question is, what are the possibilities to fill the tableViews with the data and what would you recommend in which situation.
Currently I have a property parentVC: SingleEventViewController in all Subviews and get the data like this:
override func loadUsers() {
//class SurePeopleTV
guard let parentController = parentVC else { return }
users = (parentController.thisEvent.eventSureParticipants?.allObjects as! [User])
finishedLoading = true
super.loadUsers()
}
.
func applyDefaultValues() {
//class EventScrollView
guard let parent = parentVC else { return }
titleLabel.text = parent.eventName
}
I'm new to programming but I got a feeling that I should not create a parentVC reference in all of my classes.
An object should not (ideally) know about its parent - if it does they are "tightly coupled". If you change the object's parent, your code may break. In your case, your parent object must have a thisEvent property.
You want your objects to be "loosely coupled", so the object doesn't know about a specific parent object.
In Swift, the usual ways to pass information "back up the chain" is to use the delegate design pattern… https://developer.apple.com/documentation/swift/cocoa_design_patterns or to use closures.
See also https://www.andrewcbancroft.com/2015/04/08/how-delegation-works-a-swift-developer-guide/ for info on delegation
First of all, if you create a reference to the parent ViewController make sure it is weak, otherwise you can run into memory management issues.
Edit: As Ashley Mills said, delegates the way to handle this
The recommended way to pass data between ViewControllers is using something like this
Every time a segue is performed from the view controller this function is in this function is called. This code first checks what identifier the segue has, and if it is the one that you want, you can access a reference to the next view controller and pass data to it.
Does anybody know if there is a certain pattern for handling segues programmatically in a MVC way?
I would think the best way would be to work with an event system within a controller.
I want that all the view controllers connect to this navigationController instead of handling all the logic within the viewController logic itself. I want to out source this logic
In most of your view controllers, you will have access to a prepareForSegue function, with one parameter called sender.
If you kick off a segue programatically with performSegue(withIdentifier: "mySegueID", sender: yourVC) then this function will be called, and you'll be able to pass information from the sender to the new view controller.
In this function, to get a handle on the next VC, use segue.destinationViewController.
I don't know about a particular pattern but a simple way to programmatically handle transitions between 2 UIViewController could be to have a separated manager whose job is just to push/present/whatever new controllers over current, and to pop/dismiss/whatever current controllers to old ones.
The way I usually do this is by having a class we can name WorkflowManager, which will handle all transitions. Associated with this manager, you declare a WorkflowManagerComponent protocol and implement it :
protocol WorkflowManagerComponent {
var completionHandler: (hasCompleted:Bool,data:Any)->() {get set}
}
Make each UIViewController implement this, for example by calling completionHandler(true,someData) when the user taps a "next" button, or completionHandler(false,nil) when the user taps a "back" button.
Then in your workflow manager, you perform transitions to the next or previous UIViewController according to parameters sent in the completionHandler:
//init viewController1 ...
viewController1.completionHandler = onViewController1Completes
// ...
func onViewController1Completes(_ completed: Bool, data: Any) {
if hasCompleted {
//init viewController2 ...
viewController2.data = data
viewController2.completionHandler = onViewController2Completes
//Push the new vc
viewController1.navigationController.push(viewController2, animated: true)
} else {
//The vc1 was presented as a modal, dismiss it
viewController1.dismiss()
}
}
This way each UIViewController is separated from others, free off any transition logic.
The issue I'm having is this.
I have a navigation controller with 3 viewController. In the 1st controller, I have the user select an image. This image is passed to 2nd and 3rd controller via prepareForSegue.
At the 3rd controller, I have a button that takes the user back to the 1st view controller. I explored 2 ways in doing this:
1) use performSegue, but I don't like this because it just push the 1st controller to my navigation stack. So I have this weird "Back" button at the 1st Viewcontroller now, which is not what I want. I want the app to take user directly to 1st viewcontroller without the back button.
2) I tried Poptorootviewcontroller. This solves the issue of the "back" button. But, when I pop back to the 1st viewcontroller, the user's selected image is still on screen. I want to clear this image when the user goes from the 3rd viewcontroller back to the 1st viewcontroller.
So with approach 2), how do I make sure all memory is refreshed and the image becomes nil in the 1st viewcontroller? Since I'm not using performSegue, 3rd viewcontroller does not have access to the 1st Viewcontroller.
For refresh, you'd have to clear it in viewWillAppear but I find this rather dangerous. Best you can do there is to create a new copy of the view controller everytime and Swift will take care of the rest. I don't know if you are using the storyboard but I would recommend using the class UIStoryboard and the function instiantiateViewControllerWithIdentifier("something") as! YourCustomVC
As long as you stay in the navigation stack, you'll not lose any of the current configurations of previous View Controllers.
As for passing data back to the first controller. You can either just throw it in the global scope which is the easiest way but might be difficult to know when it was updated or if the data is fresh. But you can always just:
var something: String = ""
class someView: UIViewController {
override func viewDidLoad() {
super.viewDidLoad()
something = "foo"
}
}
Something will be availabe everywhere then.
You could make a protocol and pass the delegate along the 3 view controllers. So when you are starting it you could do:
func someAction() {
let v = SomeViewController()
v.delegate = self
self.navigationController?.pushViewController(v, animated: true)
}
And then with each following view:
func someOtherAction() {
let v = SomeOtherViewController()
v.delegate = self.delegate
self.navigationController?.pushViewController(v, animated: true)
}
Although personally I find it hard to keep track of this.
Lastly you could use the NSNotificationCenter to pass an object along with all the data and catch it in a function on your first controller.
To do this you first register your VC for the action in viewDidLoad() or something:
NSNotificationCenter.defaultCenter().addObserver(self, selector: "someAction:", name: "someNotification", object: nil)
Then when you are done in the 3rd view make some object or a collection of string and send it back as follows:
NSNotificationCenter.defaultCenter().postNotificationName("someNotification", object: CustomObject())
And then lastly you'll catch it in the function "someAction"
func someAction(note: NSNotification) {
if let object = note.object as? CustomObject {
//Do something with it
}
}
Hope this helps!
Use an unwind segue which provides the functionality to unwind from the 3rd to the 1st (root) view controller.
The unwind segue is tied to an action in the root view controller. Within this action, you simply nil the image:
#IBAction func unwindToRootViewController(sender: UIStoryboardSegue)
{
let sourceViewController = sender.sourceViewController
// Pull any data from the view controller which initiated the unwind segue.
// Nil the selected image
myImageView.image = nil
}
As you can see in the action, segues also let you pass data back from the source view controller. This is a much simpler approach than needing to resort to using delegates, notifications, or global variables.
It also helps keep things encapsulated, as the third view controller should never need to know specifics about a parent view controller, or try to nil any image that belongs to another view controller.
In general, you pass details to a controller, which then acts on it itself, instead of trying to manipulate another controller's internals.
When I go to a viewController I call within my viewDidAppear Method a function:
override func viewDidAppear(animated: Bool) {
getLessons()
}
This methods loads from parse.com a list of data I want to use in a pickerView.
The function itself:
func getLessons(){
var query = PFQuery(className:"Lesson")
query.orderByAscending("name")
query.findObjectsInBackgroundWithBlock {
(objects: [AnyObject]!, error: NSError!) -> Void in
if error == nil {
for object in objects {
var name = object["name"] as String
self.languagePickerKeys.append(object.objectId)
self.languagePickerValues.append(name)
self.selectedLanguage.text = self.languagePickerValues.first // set the first lessons name into the text field
self.selectedLessonObjectId = self.languagePickerKeys.first // set the first objectId for the lesson
self.languagePicker?.reloadAllComponents()
}
} else {
// Log details of the failure
println("\(error.userInfo)")
}
}
println("getLessons done")
}
The thing is, that the textfield is empty, as the getLesson() gets the data async and the data is not available to the textfield.
I also tried to put the getLesson into the viewDidAppear method, but this doesn't help me, the textfield is empty anyway.
What can I do, to have the data from the getLessons() method ready and loaded its first value into my textfield when the view is shown to the user?
You certainly have to get the data from asyncTask before setting it to pickerView.
Here's the ViewController lifecycle after instantiation:
Preparation if being segued to.
Outlet setting
Appearing and Disappearing.
So, you have two options:
Load the data in previous ViewController and then perform the segue. You need to follow these steps for it.
a. Create a segue from previous ViewController to your ViewController.
b. Call the function when you want to go next ViewController which fetches the data, and the end (after getting the data) call performSegueWithIdentifier which will lead to your ViewController.
c. Set the data in prepareForSegue
let navigationController = segue.destinationViewController as UINavigationController
navigationController.data = yourData //you got from async call
Now when you reach your ViewController, you are sure that your data is present, and you can set it to your pickerView.
If you want to do it in the same ViewController: here's is the lifeCycle of ViewController:so you need to call your function in viewDidLoad, and always set your pickerView after completion of the async network call.
Make sure that you initiate all changes to the UI from the main thread e.g. like so:
dispatch_async(dispatch_get_main_queue(), {
selectedLanguage.text = languagePickerValues.first
self.languagePicker?.reloadAllComponents()
})
The problem is that findObjectsInBackgroundWithBlock is an asynchronous method, so even if you fire it in the ViewDidLoad you will never know when you will receive the response data and you can't be sure that the data will be ready by the time you view appear.
I think you have just 2 possibility:
The first one is to load the data in the previous view controller and then just pass the data that got ready to you view controller.
The second is to use a synchronous method (the findobject method maybe?) and put the call in a method that is fired BEFORE the view appear (like the viewWillAppear: method). But your view will stuck for a moment (I think) while the data is retreiving... However this second solution probably resolve your problem but using synchronous method to retrieve data from a slower data source is usually bad design solution.
D.
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.