How to run code when swiftui gesture recognizers begin

Question

SwiftUI MagnificationGesture and DragGesture have .onChanged and .onEnded APIs but nothing to check when the gesture started like in UIKit. Couple ways I thought to do it:

• .$gestureStarted bool in onChanged and then set it back to false in .onEnded
• use a gesture sequence with tap.

Am I missing some preferred way to do this? Seems like a pretty natural thing to want to check.

Answer 1

There is special @GestureState, which can be used for such purpose. So, here is possible approach

struct TestGestureBegin: View {

    enum Progress {
        case inactive
        case started
        case changed
    }
    @GestureState private var gestureState: Progress = .inactive // initial & reset value

    var body: some View {
        VStack {
            Text("Drag over me!")
        }
        .frame(width: 200, height: 200)
        .background(Color.yellow)
        .gesture(DragGesture(minimumDistance: 0)
            .updating($gestureState, body: { (value, state, transaction) in
                switch state {
                    case .inactive:
                        state = .started
                        print("> started")
                    case .started:
                        state = .changed
                        print(">> just changed")
                    case .changed:
                        print(">>> changing")
                }
            })
            .onEnded { value in
                print("x ended")
            }
        )
    }
}