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SOLVED: Update view when CoreData fetched item property is changed

Forums > SwiftUI

@Cryv  

Hello I need some more help.

I have a CoreData model named Item, which in turn has some properties like name, price, quantity

The items are store in an array placed in the model of the app

struct PosViewModel {
    let persistenceController = PersistenceController.shared
    let container: NSPersistentContainer
    let viewContext: NSManagedObjectContext

    var ticket: [Item] = []

    init() {
        container = persistenceController.container
        viewContext = container.viewContext

        let request = NSFetchRequest<Category>(entityName: "Category")
        request.sortDescriptors = [NSSortDescriptor(keyPath: \Category.name, ascending: true)]

        do {
            categories = try viewContext.fetch(request)
          } catch let error as NSError {
            print("Could not fetch. \(error), \(error.userInfo)")
          }
    }
}

When i change the property of the item like

ticket[index].quantity += 1

The view does not update

For now I'm using a very ugly workaround like this:

ticket.append(Item(context: viewContext))
ticket.popLast()

With this in place the view updates cause I add and remove an element from the array

Of course PosViewModel is declared as @Published in my ViewModel class, the other stuff works and the views update normally but not when i change a property inside the coredata item.

Thank you

   

hi,

Item is an object (a class), so changing one of its properties/Core Data attributes does not register as a change to the ticket array ... the object references in the array remain the same. and that's why your ugly workaround is required.

put a method in your ViewModel such as this to make a quantity increment and have it publish the change:

func incrementQuantity(for item: Item) {
  item.quantity += 1
  objectWillChange.send()
}

hope that helps,

DMG

1      

@Cryv  

Oh my god it was this easy. This worked gread thank you very much!

   

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