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How to create gesture chains using sequenced(before:)

Paul Hudson    @twostraws   

Updated for Xcode 12.5

SwiftUI lets us create new gestures out of sequences of other gestures, which allows us to trigger an action only when two gestures occur back to back – for example if the user drags a view then long-presses on it.

Because the sequenced views need to be able to reference each other, you can’t really create them as properties of your view. Instead, create them directly inside your body property, then use firstGesture.sequenced(before: secondGesture) to chain the two together into a single gesture.

As an example, this next code requires you to long press on the text view before dragging it:

struct ContentView: View {
    @State private var message = "Long press then drag"

    var body: some View {
        let longPress = LongPressGesture()
            .onEnded { _ in
                message = "Now drag me"
            }

        let drag = DragGesture()
            .onEnded { _ in
                message = "Success!"
            }

        let combined = longPress.sequenced(before: drag)

        Text(message)
            .gesture(combined)
    }
}

As you can see, I’ve made the text view update as the two gestures happen, so if you try it out you’ll be able to follow the progress of the gesture sequence.

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