37.3 The onChange Action Callback

In the previous examples, the onEnded action closure was used to detect when a gesture completes. Many of the gesture recognizers (except for TapGesture) also allow the addition of an onChange action callback. The onChange callback will be called when the gesture is first recognized, and each time the underlying values of the gesture change, up until the point that the gesture ends.

The onChange action callback is particularly useful when used with gestures involving motion across the device display (as opposed to taps and long presses). The magnification gesture, for example, can be used to detect the movement of touches on the screen.

struct ContentView: View {

 

    var body: some View {

 

    let magnificationGesture =

                  MagnificationGesture(minimumScaleDelta: 0)

...