Passing Value to a Another View: Using State and Binding In SwiftUI-CodePudding

I am trying to pass a value from my View LingView, to another View ContentView. I have a state variable in the login view as such:

@State var userName: String = ""
  @State private var password: String = ""

I then pass the value from the Content View Constructor in two places: This is in RootView

var body: some View {
      ContentView(userName: LoginView().$userName)
      .fullScreenCover(isPresented: $authenticator.needsAuthentication) {
        LoginView()
          .environmentObject(authenticator) // see note
      }
  }

This is in Content View:

struct ContentView_Previews: PreviewProvider {
    static var previews: some View {
        ContentView(userName: Login().$userName)
            .environmentObject(Authenticator())
    }
}

I want to use the variable to pass into the getPictures() function that a database file uses. I am kind of confused as to what I am suppose to do. The parent view in this case would be LoginView correct? I am unsure why I keep getting: Cannot find type 'userName' in scope.

@Binding var userName: String
    
    print(userName)
    
    
    var pictureURL = DbHelper().getPictures()

After running the following code. I understand that you should make state private to a View, but in this case how would I pass the state value to the content view? The LoginView does not call the ContentView directly. Maybe I don't understand Bindings and State, but I have read this article: https://learnappmaking.com/binding-swiftui-how-to/

CodePudding user response：

You are initialising two separate login views. The username binding passed to ContentView is therefore a different binding to the one you have under .fullscreenCover

To make it work, you can declare a State variable in RootView,

@State private var userName: String = "" // In RootView

then pass its binding to both ContentView and LoginView.

@Binding var userName: String // In ContentView and LoginView

Simply put, State holds your actual username value, while Binding gives you a method of seeing and changing it from somewhere else.