Looping through entities which describe what action should be taken on screen after keypresses - swift

Question

Please forgive me if I don't describe this question too well, I am new to programming MacOS apps using Swift. I know the way I'm going about this is probably wrong and I just need someone to tell me the right way.
My main app screen
I have a Core Data application that stores an ordered list of entities called Items. These Items are intended to describe a single step in an activity that describes what should happen on screen. If you know the Mac application QLab each Item is like a single cue in QLab.
I have created an Activity class that is designed to read through each Item to determine the Item type and it's related information. Once the Item type has been determined the Activity class needs to present a View with information related to that particular Item and then wait until the user presses the right arrow key to then proceed to the next Item in the Core Data store where the process repeats until all Items have been read. Each time a new Item is read in the loop, the information on the screen should change after the user presses the right arrow each time.
The problem is that I don't know exactly how the best way of going about this should be programatically speaking. I have the code that retrieves the array of Items as an NSFetchRequest:
let moc = (NSApplication.shared.mainWindow?.contentViewController?.representedObject as! NSPersistentDocument).managedObjectContext!
let fetchRequest : NSFetchRequest = Item.fetchRequest()
do {
let items = try moc.fetch(fetchRequest)
print("Found " + String(items.count) + " items to use in the activity.")
for item in items {
print(item.itemType)
// How do I pause this loop for a user keypress after using data from this Item to display?
}
} catch {
print("Error retrieving Items")
}
I can retrieve the keydown event using NSEvent.addLocalMonitorForEvents(matching: .keyDown) and I'm also able to create View Controllers to display the information on a second screen. I just don't know how I should create the 'main loop', so to speak, so that information is displayed and then the app waits until the user presses a key to proceed...
I can share my project code if more information is needed and many thanks to anyone who can enlighten me... :)

Answer 1

You could try using a NSPageController. In your NSPageController you add a ContainerView which will display the ViewControllers that display information for each item. Each ViewController will need a storyboard identifier, e.g. ViewControllerItem1.
Your NSPageController class must conform to the NSPageControllerDelegate protocol and contains an array of ViewControllers to display.
override func viewDidLoad() {
super.viewDidLoad()
delegate = self
arrangedObjects = ["ViewControllerItem1", "ViewControllerItem2", "...","ViewControllerItemN" ]
}
Note about arrangedObjects from the NSPageController documentation: An array containing the objects displayed in the page controller’s view.
Then you implement NSPageControllers viewControllerForIdentifier to return the ViewController that you currently want to display in the ContainerView.
func pageController(_ pageController: NSPageController, viewControllerForIdentifier identifier: String) -> NSViewController {
switch identifier {
case "ViewControllerItem1":
return mainStoryboard().instantiateController(withIdentifier:"ViewControllerItem1") as? ViewControllerItem1
case "...":
default:
}
}
In your action handler for the key down event you implement.
self.navigateForward(sender) or self.navigateBack(sender)
I also implemented this method but I don't remember whether it was required.
func pageControllerDidEndLiveTransition(_ pageController: NSPageController) {
self.completeTransition()
}