How to present an Alert with swiftUI

问题

In swiftUI I discovered the Alert type. But I wonder how to show it with the presentation method.

Initializing an Alert is pretty easy. But how to use the binding?

struct ContentView : View {
    var body: some View {
        Button(action: {
            // Don't know how to use the `binding` below
            presentation(binding, alert: {
                Alert(title: Text("Hello"))
            })
        }, label: {
            Text("asdf")
        })
    }
}

The binding is of type Binding<Bool>

回答1:

You can use a @State variable as the binding. Alternatively you can use a @EnvironmentObject variable that uses a BindableObject.

I think you need to call presentation on the root View to get it to work, adding it to a Stack, Group, etc. doesn't seem to work.

This snippet seems to do the trick. Note that @State variable is set to false after the alert is dismissed.

struct ContentView: View {

    @State var showsAlert = false

    var body: some View {
        Button(action: {
            self.showsAlert = true
        }, label: {
            Text("asdf")
        }).presentation($showsAlert, alert: {
            Alert(title: Text("Hello"))
        })
    }
}

回答2:

.presentation() was actually deprecated in Beta 4. Here is a version that currently works with the .alert() Modifier.

struct ContentView: View {
    @State var showsAlert = false
    var body: some View {
        Button(action: {
            self.showsAlert.toggle()
        }) {
            Text("Show Alert")
        }
        .alert(isPresented: self.$showsAlert) {
            Alert(title: Text("Hello"))
        }
    }
}

回答3:

Full Code of Alert with dismiss and okay action:

Code:

import SwiftUI

struct ContentView: View {
    @State private var isAlert = false

    var body: some View {
            Button(action: {
                self.isAlert = true
            }) {
                Text("Click Alert")
                .foregroundColor(Color.white)
            }
            .padding()
            .background(Color.blue)
            .alert(isPresented: $isAlert) { () -> Alert in
                Alert(title: Text("iOSDevCenters"), message: Text("This Tutorial for SwiftUI Alert."), primaryButton: .default(Text("Okay"), action: {
                    print("Okay Click")
                }), secondaryButton: .default(Text("Dismiss")))
        }

    }
}

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

Output:

Output

回答4:

struct ContentView: View {

    @State var aAlert = false

    var body: some View {
        Text("Alert").tapAction {
            self.aAlert = true
        }.presentation($aAlert, alert:{ Alert(title: Text("Alert"))})
    }
}

回答5:

In addition to @tsp's answer, to display an alert with two buttons and handle button tap action, you can do as below:

@State var showAlert = false

var body: some View {
  Button(action: {
    self.showAlert = true
  }) {
    Text("Show Alert")
  }
  .presentation($showAlert) {
      Alert(title: Text("Title"), message: Text("Message..."),
          primaryButton: .default (Text("OK")) {
            print("OK button tapped")
          },
          secondaryButton: .cancel()
      )
  }
}

Result:

来源：https://stackoverflow.com/questions/56448388/how-to-present-an-alert-with-swiftui

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swift

swiftui

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