View will lose data of ObservedObject in a fullScreenCover when EditMode changes

Question

Created May ’21

Replies 2

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Views 1.3k

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I've created a view with a TextField and an EditButton. When I open this view in a fullScreenCover with the editMode active than the input text disappears when the Done-Button is tapped.

This behavior is appearing when a @ObservedObject is used. When a @State variable is used for the TextField then everything is fine.

This is the view

Code Block Swiftstruct ProfileView: View {
	@ObservedObject
	var viewModel = ProfileViewModel()
	@Environment(\.editMode) var editMode
	@State
	var name = ""
	var body: some View {
		VStack {
			Text("@State")
			TextField("TextField", text: $name)
				.disabled(editMode?.wrappedValue == .inactive)
			Text("@ObservedObject")
			TextField("TextField", text: $viewModel.name)
				.disabled(editMode?.wrappedValue == .inactive)
			Spacer()
		}
		.padding()
		.toolbar {
			ToolbarItem(placement: .navigationBarTrailing) {
				EditButton()
			}
		}
	}
}

Using

Code Block Swiftclass ProfileViewModel: ObservableObject {
	@Published var name: String = ""
}

This is the view which is presenting

Code Block Swiftstruct ContentView: View {
	@State
	var isPresentingEmtpyProfile: Bool = false
	var body: some View {
		NavigationView {
			List {
				NavigationLink(destination: ProfileView()) {
					Text("ProfileView")
				}
			}
			.toolbar {
				ToolbarItem(placement: .navigationBarTrailing) {
					Button(action: {
						isPresentingEmtpyProfile = true
					}) {
						Image(systemName: "plus")
					}
				}
			}
			.navigationBarTitle("Navigation", displayMode: .inline)
			.fullScreenCover(isPresented: $isPresentingEmtpyProfile) {
				NewProfileViewWithNavigation(isPresentingEmptyProfile: $isPresentingEmtpyProfile)
			}
		}
	}
}
extension ContentView {
	struct NewProfileViewWithNavigation: View {
		@State
		private var editMode = EditMode.active 
		@Binding
		var isPresentingEmptyProfile: Bool
		var body: some View {
			NavigationView {
				ProfileView()
					.navigationBarTitleDisplayMode(.inline)
					.toolbar {
						ToolbarItem(placement: .cancellationAction) {
							Button(action: {
								isPresentingEmptyProfile = false
							}) {
								Text("Close")
							}
						}
						ToolbarItem(placement: .principal) {
							Text("New Profile")
						}
					}
					.environment(\.editMode, $editMode)
			}
		}
	}
}

Does anyone have an idea why this is happening?

Answered by OOPer in 673131022

@ObservedObject properties may be re-initialized at each time the containing view is initialized. And it is hard to predict when views are initialized in SwiftUI.

Have you tried @StateObject?

Code Block     @StateObject
    var viewModel = ProfileViewModel()

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Answer 1

OOPer OP

May ’21

Accepted Answer

@ObservedObject properties may be re-initialized at each time the containing view is initialized. And it is hard to predict when views are initialized in SwiftUI.

Have you tried @StateObject?

Code Block     @StateObject
    var viewModel = ProfileViewModel()

0

Answer 2

1010011010 OP

May ’21

Thank so much. This helped. In my case it makes sense to use @StateObject because the view creates and owns the view model. @ObservedObject is used when someone else is holding the observed object.

0