swiftui_memory_leak_issue_demo

ContentView.swift

//
//  ContentView.swift
//  Shared
//
//  Created by Frank V on 2022/3/30.
//

import SwiftUI

class TestViewModel_A: ObservableObject {
    func refresh() async {
        //Do some refresh thing
        
        try? await Task.sleep(nanoseconds: 200_000_000)
    }
}

class TestViewModel_B: TestViewModel_A {}
class TestViewModel_C: TestViewModel_A {}

struct ContentView: View {
    @StateObject var viewModel = TestViewModel_A()
    
    var body: some View {
        NavigationView {
            List {
                NavigationLink("NextView") {
                    NextView()
                }
            }
            .navigationTitle("Test Title")
            .navigationBarTitleDisplayMode(.automatic)
        }
    }
}

/*
 This view is using `.navigationBarTitleDisplayMode(.automatic)` and
 call a function in it's view model from `.refreshable()`.
 
 The `viewModel` will never deinit
 */
struct NextView: View {
    @StateObject var viewModel = TestViewModel_B()
    
    var body: some View {
        List {
            NavigationLink("AnotherView") {
                AnotherView()
            }
        }
        .navigationTitle("Next Title")
        .navigationBarTitleDisplayMode(.automatic)
        .refreshable {
            await viewModel.refresh()
        }
    }
}

/*
 This view using `.navigationBarTitleDisplayMode(.inline)` and have no
 issue with `.refreshable()`
 */
struct AnotherView: View {
    @StateObject var viewModel = TestViewModel_C()
    
    var body: some View {
        
        List {
            VStack {
                Text("Last view")
            }
        }
        .navigationTitle("Another Title")
        .navigationBarTitleDisplayMode(.inline)
        .refreshable {
            await viewModel.refresh()
        }
    }
}

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