Implementing an interactive transition requires a bit more work than the non-interactive presentation animation, and the way it works is also somewhat harder to grasp. For the non-interactive transition, transitioningDelegate simply returns an animation controller from animationController(forPresented:presenting:source:).
To implement an interactive dismiss transition, two methods should be implemented. These two methods work together to make the interactive animation happen. The first method is animationController(forDismissed:). This method will return an object that performs and controls the interactive animation, similar to the animation controller you implemented before.
However, to make the ...
