SwiftUI retain cycle with .searchable

Question

Created Mar ’22

Replies 2

Boosts 1

Views 1.1k

Participants 2

I'm trying to see what I am doing wrong ... So I created this simple app where the stateobject Retainer won't get deallocated when I pop the view off the stack:

import SwiftUI

struct ContentView: View {
    
    var body: some View {
        NavigationView {
            List {
                NavigationLink("To Retain Cycle") {
                    RetainCycleView()
                }
            }
            .navigationTitle("Retain Cycle Demo")
        }
        .navigationViewStyle(.stack)
    }
}
    
struct RetainCycleView: View {
    
    @StateObject var model = Retainer()
//    @State var enteredText: String = ""
    
    var body: some View {
        VStack(alignment: .leading, spacing: 4) {
            Text("Navigate back to the previous view.")
            Text("You will see that 'Retainer' was NOT deallocated.")
            Text("(it's deinit function prints deallocing Retainer)")
                .font(.callout)
        }
        .padding()
        .searchable(text: $model.enteredText)
//       ^---- retain cycle
//        .searchable(text: $enteredText)
//       ^---- no retain cycle when using the @State var
    }
}

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}

class Retainer: ObservableObject {
    
    @Published var enteredText: String = ""
    
    init() { print("instantiated Retainer") }
    deinit { print("deallocing Retainer") }
}

I filed feedback but I am not entirely sure that this isn't me making some mistake ...

Please help me

Boost

Answer 1

MobileTen OP

Mar ’22

If you do this then there is no need to create a new object model on each push. It is created once and destroyed once on app exit:

@main
struct MyApp: App {
    @StateObject var model = Retainer()
    var body: some Scene {
        WindowGroup {
            ContentView()
                .environmentObject(model)
        }
    }
}

struct RetainCycleView: View {
    @EnvironmentObject var model: Retainer
    var body: some View {
        VStack(alignment: .leading, spacing: 4) {
            Text("Navigate back to the previous view.")
            Text("You will see that 'Retainer' was NOT deallocated.")
            Text("(it's deinit function prints deallocing Retainer)")
                .font(.callout)
        }
        .padding()
        .searchable(text: $model.enteredText)
        .onChange(of: model.enteredText) { newValue in
            print("Searching for: ", newValue)
        }
    }
}

0

Answer 2

RonnyF OP

Mar ’22

Yes that makes sense. Now the search model is created in the ancestor view ... I think that would be less ideal. The model is very light weight and essentially only providing a bindable publisher and some (web) search functionality ... this probably doesn't need to outlive that view and it would be ok to create a new model alongside a view push ...

Interestingly a TextField with the same binding to Retainer would behave as expected ... the model would be deallocated when the view is removed from the view stack ...

0