swift5.1

The SwiftUI tutorial uses the @State keyword to indicate mutable UI state: @State var showFavoritesOnly = false It offers this summary: State is a value, or a set of values, that can change over time, and that affects a view’s behavior, content, or layout. You use a property with the @State attribute to add state to a view. What does the keyword mean, exactly? How does mutating a @State variable cause the view to be recomputed? How are other variables immutable within the body getter? The @State keyword is a @propertyWrapper , a feature just recently introduced in Swift 5.1. As explained in

The new SwiftUI tutorial has the following code: struct ContentView: View { var body: some View { Text("Hello World") } } The second line the word some , and on their site is highlighted as if it were a keyword. Swift 5.1 does not appear to have some as a keyword, and I don't see what else the word some could be doing there, since it goes where the type usually goes. Is there a new, unannounced version of Swift? Is it a function that's being used on a type in a way I didn't know about? What does the keyword some do? some View is an opaque result type as introduced by SE-0244 and is available