Gestures on iOS can be either discrete or continuous. That is to say recognition can be instantaneous (e.g. tap gesture) or take time to determine that the gesture succeeded (e.g. drawing a square).
This is a quick demo of writing a custom UIGestureRecognizer for iOS which recognizes a continuous gesture, in particular pressing a finger down for one second and then dragging the finger around.
To run this, clone this repository and launch the project as an iPad project using XCode.
If you see anything that would make this more useful as a pedagogical tool, please feel free to send me a pull request with a brief explanation of your changes.