Reduce API surface.

[andersio]

Depends on #2.

The public DrawerKit API has been reduced to three pieces: DrawerConfiguration, DrawerController and PartiallyExpandableDrawer.

A view controller that wishes to be presented as a drawer can simply:

1. create and retain DrawerController with its desired configuration; and
2. set the DrawerController as its transitioning delegate.

If it wishes to support partial expansion, on top of enabling the setting in DrawerConfiguration, the drawer view controller needs to conform to also PartiallyExpandableDrawer.

How does it work?

DrawerController tracks if it has ever created any PresentationController. Since UIKit pretty much guarantees that it asks for a presentation controller before the animators, we can explore this in order to retrieve the presenting VC for the animator dynamically.

It also works when the view controller is recycled. Since UIKit would release the presentation controller upon conclusion of a presentation, this means the weak reference in DrawerController would be zeroed, and hence a new PresentationController would be created next time the drawer is presented.

Example

https://github.com/Babylonpartners/DrawerKit/pull/3/files#diff-797161087489cdf11d7916a4480c4f93R4

Basic hello world example:

drawerController = DrawerController(configuration: DrawerConfiguration())
modalPresentationStyle = .custom
transitioningDelegate = drawerController

[diegopetrucci]

Why is this blocked?

[wltrup]

I'm making some significant changes and adding some new or missing features to DrawerKit this weekend (PR forthcoming sometime today or tomorrow) and I think it would be best to wait after those are reviewed and merged before considering reducing the API surface. Besides, this branch has conflicts so they need to be resolved before any review is to happen. 😄