openURL

Discussion 議論

Read this environment value to get an OpenURLAction instance for a given Environment. Call the instance to open a URL. You call the instance directly because it defines a callAsFunction(_:) method that Swift calls when you call the instance.

For example, you can open a web site when the user taps a button:

struct OpenURLExample: View {
    @Environment(\.openURL) private var openURL


    var body: some View {
        Button {
            if let url = URL(string: "https://www.example.com") {
                openURL(url)
            }
        } label: {
            Label("Get Help", systemImage: "person.fill.questionmark")
        }
    }
}

If you want to know whether the action succeeds, add a completion handler that takes a Boolean value. In this case, Swift implicitly calls the callAsFunction(_:completion:) method instead. That method calls your completion handler after it determines whether it can open the URL, but possibly before it finishes opening the URL. You can add a handler to the example above so that it prints the outcome to the console:

openURL(url) { accepted in
    print(accepted ? "Success" : "Failure")
}

The system provides a default open URL action with behavior that depends on the contents of the URL. For example, the default action opens a Universal Link in the associated app if possible, or in the user’s default web browser if not.

You can also set a custom action using the environment(_:_:) view modifier. Any views that read the action from the environment, including the built-in Link view and Text views with markdown links, or links in attributed strings, use your action. Initialize an action by calling the init(handler:) initializer with a handler that takes a URL and returns an OpenURLAction.Result:

Text("Visit [Example Company](https://www.example.com) for details.")
    .environment(\.openURL, OpenURLAction { url in
        handleURL(url) // Define this method to take appropriate action.
        return .handled
    })

SwiftUI translates the value that your custom action’s handler returns into an appropriate Boolean result for the action call. For example, a view that uses the action declared above receives true when calling the action, because the handler always returns handled.