SwiftUI onAppear在NavigationView inside TabView时调用了两次

import SwiftUI

struct ContentView: View {
    @StateObject private var viewModel = ViewModel()

    var body: some View {
        TabView {
            NavigationView {
                Text("Tab 1")
                    .onAppear {
                        viewModel.didAppear()
                    }
                    .navigationTitle("Tab 1")
            }
            .tag(0)

            NavigationView {
                Text("Tab 2")
                    .onAppear {
                        viewModel.didAppear()
                    }
                    .navigationTitle("Tab 2")
            }
            .tag(1)
        }
    }
}

class ViewModel: ObservableObject {
    @Published var appeared = false

    func didAppear() {
        if !appeared {
            appeared = true
            print("onAppear called")
        }
    }
}