callAsFunction(_:completion:)

Declaration

@MainActor @preconcurrency func callAsFunction(_ url: URL, completion: @escaping (Bool) -> Void)

Parameters

• url:

  The URL to open.

• completion:

  A closure the method calls after determining if it can open the URL, but possibly before fully opening the URL. The closure takes a Boolean value that indicates whether the method can open the URL.

Discussion

Don’t call this method directly. SwiftUI calls it when you call the OpenURLAction structure that you get from the Environment, using a URL and a completion handler as arguments:

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

    var body: some View {
        Button {
            if let url = URL(string: "https://www.example.com") {
                // Implicitly calls openURL.callAsFunction(url) { ... }
                openURL(url) { accepted in
                    print(accepted ? "Success" : "Failure")
                }
            }
        } label: {
            Label("Get Help", systemImage: "person.fill.questionmark")
        }
    }
}

For information about how Swift uses the callAsFunction() method to simplify call site syntax, see Methods with Special Names in The Swift Programming Language.

See Also

Calling the action

• callAsFunction(_:)