Detect change in NSMutableOrderedSet with Combine

Question

Created Jul ’20

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I'm trying to observe change of an NSMutableOrderedSet in my ViewModel with combine. I want to know when some element is added or removed of NSMutableOrderedSet
Some code of my ViewModel :

Code Block class TrainingAddExerciceViewModel: ObservableObject {
				
				@Published var exercice: Exercice?
				@Published var serieHistories = NSMutableOrderedSet()
		
		...
			init(...) {
				...
				
//Where i'm trying to observe 
				$serieHistories
						.sink { (value) in
								print(value)
				}
				.store(in: &self.cancellables)
		}
		
		}

This is the function I use in my ViewModel to add element to NSMutableOrderedSet :

Code Block func add(managedObjectContext: NSManagedObjectContext) {
				let newSerieHistory = ExerciceSerieHistory(context: managedObjectContext)
				self.serieHistories.add(newSerieHistory)
				self.updateView()
		}

I have some other publisher working well with an other type (custom class).
Did I miss something ?

Thanks

Answered by langy in 624812022

I got answer :

it doesn't work with NMutableOrderedSet because it's a reference-type - a class. (https://developer.apple.com/documentation/foundation/nsmutableorderedset)

Solution is to edit add() like this :

Code Block func add(managedObjectContext: NSManagedObjectContext) {
				let newSerieHistory = ExerciceSerieHistory(context: managedObjectContext)
				let newStorage = NSMutableOrderedSet(orderedSet: self.serieHistories)
				newStorage.add(newSerieHistory)
				self.serieHistories = newStorage		 // << fires publisher
				self.updateView()
		}

Boost

Answer 1

langy OP

Jul ’20

Accepted Answer

I got answer :

it doesn't work with NMutableOrderedSet because it's a reference-type - a class. (https://developer.apple.com/documentation/foundation/nsmutableorderedset)

Solution is to edit add() like this :

Code Block func add(managedObjectContext: NSManagedObjectContext) {
				let newSerieHistory = ExerciceSerieHistory(context: managedObjectContext)
				let newStorage = NSMutableOrderedSet(orderedSet: self.serieHistories)
				newStorage.add(newSerieHistory)
				self.serieHistories = newStorage		 // << fires publisher
				self.updateView()
		}

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