Instance Method インスタンスメソッド

alert(_:isPresented:presenting:actions:message:)

Presents an alert with a message using the given data to produce the alert’s content and a string variable as a title.

Declaration 宣言

func alert<S, A, M, T>(_ title: S, isPresented: Binding<Bool>, presenting data: T?, actions: (T) -> A, message: (T) -> M) -> some View where S : StringProtocol, A : View, M : View

Parameters パラメータ

title: A text string used as the title of the alert.
isPresented: A binding to a Boolean value that determines whether to present the alert. When the user presses or taps one of the alert’s actions, the system sets this value to false and dismisses.
data: An optional source of truth for the alert. The system passes the contents to the modifier’s closures. You use this data to populate the fields of an alert that you create that the system displays to the user.
actions: A ViewBuilder returning the alert’s actions given the currently available data.
message: A ViewBuilder returning the message for the alert given the currently available data.

Discussion 議論

For the alert to appear, both isPresented must be true and data must not be nil. The data should not change after the presentation occurs. Any changes that you make after the presentation occurs are ignored.

Use this method when you need to populate the fields of an alert with content from a data source. The example below shows a custom data source, SaveDetails, that provides data to populate the alert:

struct SaveDetails: Identifiable {
    let name: String
    let error: String
}
struct SaveView: View {
    var title: String
    @State var didError = false
    @State var details: SaveDetails?
    var body: some View {
        Button("Save File") {
            details = model.save(didError: $didError)
        }
        .alert(
            title, isPresented: $didError, presenting: details
        ) { detail in
            Button(role: .destructive) {
                // Handle delete action.
            } label: {
                Text("""
                Delete \(detail.name)
                """)
            }
            Button("Retry") {
                // handle retry action.
            }
        } message: { detail in
            Text(detail.error)
        }
    }
}

All actions in an alert dismiss the alert after the action runs. The default button is shown with greater prominence. You can influence the default button by assigning it the defaultAction keyboard shortcut.

The system may reorder the buttons based on their role and prominence.

If no actions are present, the system includes a standard “OK” action. No default cancel action is provided. If you want to show a cancel action, use a button with a role of cancel.

On iOS, tvOS, and watchOS, alerts only support controls with labels that are Text. Passing any other type of view results in the content being omitted.

Only unstyled text is supported for the message.