Alert

Overview 概要

Use an alert when you want the user to act in response to the state of the app or system. If you want the user to make a choice in response to their action, use an ActionSheet instead.

You show an alert by using the alert(isPresented:content:) view modifier to create an alert, which then appears whenever the bound isPresented value is true. The content closure you provide to this modifer produces a customized instance of the Alert type.

In the following example, a button presents a simple alert when tapped, by updating a local showAlert property that binds to the alert.

@State private var showAlert = false
var body: some View {
    Button("Tap to show alert") {
        showAlert = true
    }
    .alert(isPresented: $showAlert) {
        Alert(
            title: Text("Current Location Not Available"),
            message: Text("Your current location can’t be " +
                            "determined at this time.")
        )
    }
}

To customize the alert, add instances of the Alert.Button type, which provides standardized buttons for common tasks like canceling and performing destructive actions. The following example uses two buttons: a default button labeled “Try Again” that calls a saveWorkoutData method, and a “Delete” button that calls a destructive deleteWorkoutData method.

@State private var showAlert = false
var body: some View {
    Button("Tap to show alert") {
        showAlert = true
    }
    .alert(isPresented: $showAlert) {
        Alert(
            title: Text("Unable to Save Workout Data"),
            message: Text("The connection to the server was lost."),
            primaryButton: .default(
                Text("Try Again"),
                action: saveWorkoutData
            ),
            secondaryButton: .destructive(
                Text("Delete"),
                action: deleteWorkoutData
            )
        )
    }
}

The alert handles its own dismissal when the user taps one of the buttons in the alert, by setting the bound isPresented value back to false.