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SOLVED: How to pass a value between view models without using a singleton

Forums > SwiftUI
@erikbee  

Hi everyone. I am really struggling to understand how to share a value from a viewmodel to another one. I have a SettingsView that sets a value in the SettingsViewModel and I would like that value to be accessible in the DashboardViewModel and DashboardView. How can I do that without using a singleton? Here is my code:

public class SettingsViewModel: ObservableObject {
    @Published var isOn: Bool = false
}
struct SettingsView: View {

    @ObservedObject var viewModel = SettingsViewModel()

    var body: some View {
        VStack{
            List {
                Section(header: Text("Select Values")) {
                    HStack {
                        Toggle("Only PM", isOn: $viewModel.isOn)
                    }
                    HStack {
                        Text(String(viewModel.isOn))
                    }
                }
            }

        }
    }
}
public class DashboardViewModel: ObservableObject {
    var settingsViewModel: SettingsViewModel

    init(settingsViewModel: SettingsViewModel) {
        self.settingsViewModel = settingsViewModel
    }
}
struct DashboardView: View {
    var viewModel = DashboardViewModel(settingsViewModel: SettingsViewModel())

    var body: some View {
        Text(String(viewModel.settingsViewModel.isOn))
    }
}

1      

@Gakkienl  HWS+

Add SettingsViewModel to the environment in the first view you want to use it and thereafter its is accessible anywhere!

1      

@AmitShrivastava  

In your file with @main function make it like so

import SwiftUI

@main
struct DemoProjectApp: App {
    @StateObject var viewModel = SettingsViewModel()
    var body: some Scene {
        WindowGroup {
            ContentView(settingsViewModel: viewModel)

        }
    }
}

SettingsView like below 

struct SettingsView: View {

    @ObservedObject var viewModel: SettingsViewModel
    var body: some View {
        VStack{
            List {
                Section(header: Text("Select Values")) {
                    HStack {
                        Toggle("Only PM", isOn: $viewModel.isOn)
                    }
                    HStack {
                        Text(String(viewModel.isOn))
                    }
                }
            }

        }
    }
}

And now you do not need the DashBoardViewModel

Just add the DashBoardView as below and it will change as per change in toggle button

struct DashboardView: View {
    @ObservedObject var settingsViewModel: SettingsViewModel

    var body: some View {
        Text(String(settingsViewModel.isOn))
    }
}

Here like below

struct ContentView: View {
    @ObservedObject var settingsViewModel: SettingsViewModel
    var body: some View {
        SettingsView(viewModel: settingsViewModel)
        DashboardView(settingsViewModel: settingsViewModel)
    }

}

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

1      

@erikbee  

Thank you, this works. It also helped me to understand how to do it if I have, for instance, to modify a value within the DashboardViewModel and display it in the DashboardView. I have to inject it like this:

struct ContentView: View {

    @ObservedObject var settingsViewModel: SettingsViewModel

    var body: some View {
        VStack {
            SettingsView(viewModel: settingsViewModel)
            DashboardView(viewModel: DashboardViewModel(settingsViewModel: settingsViewModel))
        }
    }
}

1      

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