SwiftUI - How to programatically load a new view from the current view

Question

My App requires an initial view to be loaded programatically and not via the TabView. Here is an MRE to show the problem. The sequence is:

ContentView loads the TabMenu
The initial TabMenu View is OneView
From the tabs you can switch between OneView and TwoView

How do I get the OneView to programatically load TwoView. It currently loses the Tab Menu (final screen shot below). In the full version of my code it was crashing to @main.

ContentView

import SwiftUI

struct ContentView: View {

@State var selectedTab = TabChoice.one
@State var calculated = CalculatedChoice.falseCC

var body: some View {
    NavigationStack {
        VStack {
            // MARK: BUTTON
            Spacer()
            NavigationLink(destination: MenuView().navigationBarBackButtonHidden(true))   {
                Text("Press to launch the TabView Menu")
                    .tint(.black)
            }
            Spacer()
        }
    }
    .padding()
}
}

#Preview {
    ContentView()
}

MenuView

import SwiftUI

enum TabChoice {
    case one, two
}

enum CalculatedChoice {
    case falseCC, trueCC
}

struct MenuView: View {

@State var selectedTab = TabChoice.one
@State var calculated = CalculatedChoice.falseCC

var body: some View {
    NavigationStack {
        VStack {
            TabView(selection: $selectedTab) {
                
                OneView(selectedTab: $selectedTab, calculated: $calculated)
                    .tabItem {
                        Label("One", systemImage: "1.circle")
                    }
                    .tag(TabChoice.one)
                TwoView(selectedTab: $selectedTab, calculated: $calculated)
                    .tabItem {
                        Label("Two", systemImage: "2.circle")
                    }
                    .tag(TabChoice.two)
            }
        }
    }
}
}

OneView

import SwiftUI

struct OneView: View {

@Binding var selectedTab: TabChoice
@Binding var calculated: CalculatedChoice

var body: some View {
    VStack {
        Spacer()
        Text("TabView 1")
        Spacer()
        HStack{
            NavigationLink(destination: TwoView(selectedTab: $selectedTab, calculated: $calculated).navigationBarBackButtonHidden(true))   {
                Text("Press to Load TabView2 Programatically")
            }
        }
        Spacer()
    }
}
}

TwoView

import SwiftUI

struct TwoView: View {

@Binding var selectedTab: TabChoice
@Binding var calculated: CalculatedChoice

var body: some View {
    VStack {
        Spacer()
        Text("TabView 2")
        Spacer()
    }
    
}
}

Many thanks to lorem ipsum for politely pushing me to create an MRE so the issues are clearer to see. Screen shots below:

Why not using buttons in place of navigation links ? Also pay attention that modifying selectedTab in any view will modify it in all created views and so redraw these. — Ptit Xav, Aug 17 '23 at 17:55
Like I mentioned in the other post a TabView cannot be inside a NavigationStack (or 2 for that matter) per HIG. This is the source of many bugs and now crashes. Each tab must be independent from the rest of the tabs, they can’t share a hierarchy. — lorem ipsum, Aug 17 '23 at 19:55
But if I bring the NavigationStack() inside the TabView() in MenuView I get the two screens showing on the same page. You mention this issue a lot. Are there any examples I can follow? All the ones I have come across are simplistic and don't need the NavigationStack. — Edward Hasted, Aug 18 '23 at 07:58

score 0 · Answer 1 · answered Aug 17 '23 at 20:14

0

You can update your code like that for OneView:

struct OneView: View {
    
    @Binding var selectedTab: TabChoice
    @Binding var calculated: CalculatedChoice
    
    var body: some View {
        VStack {
            Spacer()
            Text("TabView 1")
            Spacer()
            HStack{
                Text("Press to Load TabView2 Programatically").onTapGesture {
                    selectedTab = .two
                }
            }
            Spacer()
        }
    }
}

answered Aug 17 '23 at 20:14

EsatGozcu

185
8

That introduces two TabView button 1s? .onTapGesture is a useful tool. – Edward Hasted Aug 18 '23 at 07:49
Question is not clear please give me more detail. – EsatGozcu Aug 18 '23 at 08:37
The @State var/@Binding deal with stuff in the View. I think my issue is that I want be able to make the MenuView() show a specific screen, One or Two. Because when you press a tab that is handled in the View it works. I want to be able to specify which View you see when you press a button. – Edward Hasted Aug 19 '23 at 09:30

score 0 · Answer 2 · answered Aug 19 '23 at 12:32

I have ended up using:

 Button(action: {selectedTab = TabChoice.one}, label: { Text("Press to Load TabView2 Programatically") })

This seems too simple and I am sure I tried this previously. I will delete this question shortly, unless anyone finds any merit in it. I thinks it's been a red herring and I am very grateful for everyone's help and patience.

SwiftUI - How to programatically load a new view from the current view

2 Answers2