Change boolean value inside swiftui view-CodePudding

I have boolean variable (isTapped), once the app is launched, I'am giving it a true value, once it moves to (signupView) the app should test the value inside if statement to show some text and after that the app should change the value of (isTapped) to false!!

But it is not working!! as Type () cannot confirm to view. I tried to create a function and call it inside a view but it is not working either! Here is my code:

import SwiftUI

struct SignupView: View {
@AppStorage("isTapped") var isTapped : Bool?
var body: some View {
    if (isTapped == true){
        Text ("signup")
        isTapped = false 
        
    }
    else {
        Text ("Splash")
    }

}
}

CodePudding user response：

You can't set anything to a variable inside the view hierarchy. So to achieve what you want to do, maybe you could try this:

var body: some View {
    if (isTapped == true){
        Text ("signup")
            .onAppear {
                isTapped = false 
            }
    } else {
        Text ("Splash")
    }
}

onAppear closure is run outside the view hierarchy, so you can set values to a variable.

**Update: Re: your comment, that's how SwiftUI works. When isTapped = false is set in onAppear, SwiftUI immediately reloads the body and the splash will be shown. I think to achieve what you need, you shouldn't use @AppStorage. It will cause an update of the body when it's updated. Why don't you just use UserDefaults like this?:

let isTapped: Bool? = UserDefaults.standard.bool(forKey: "isTapped")

...

Text ("signup")
    .onAppear {
        UserDefaults.standard.set(false, forKey: "username") 
    }

CodePudding user response：

If you want Text("signup") should be shown when isTapped is True, you need additional variable to keep the origin value

struct SignupView: View {
    @AppStorage("isTapped") var isTapped : Bool = false
    @State var isTappedOrigin: Bool = false
    
    var body: some View {
        Group {
            if (isTappedOrigin == true){
                Text ("signup")
            } else {
                Text ("Splash")
            }
        }.onAppear {
            isTappedOrigin = isTapped
            isTapped = false
        }
    }
}

You need to set isTapped = true somewhere to see Text("signup") like this

struct ContainView: View {
    @AppStorage("isTapped") var isTapped : Bool = false
    @State var show: Bool = false
    var body: some View {
        List {
            Toggle("isTapped", isOn: $isTapped)
            Button("show signup view") {
                show.toggle()
            }
        }
        .sheet(isPresented: $show) {
            SignupView()
        }
    }
}

If you want to show signup only once when launch app it should be like this

struct TestView: View {
    @AppStorage("isSignedUp") var isSignedUp : Bool = false
    @State var shouldShowSignUp : Bool = false
    
    var body: some View {
        Group {
            if shouldShowSignUp {
                Text("Sign Up")
            } else {
                Text("Splash")
            }
        }.onAppear {
            shouldShowSignUp = !isSignedUp
            isSignedUp = true
        }
    }
}