Presentation Controllers jesse sequires

# UIPresentation Controlers

https://realm.io/news/slug-jesse-squires-swifty-view-controller-presenters/

Transition > transiting state
Presentation > final state

Presentation hook into the transition API

responsibilities
- positioning
- managing the chrome
- adaptation


Not coupled with transition objects


3 phases
1. Presentation (moving onscreen)
2. Management (size class changes, size change, device rotation)
3. Dismissal (moving offscreen)
+ Transitioning

modalPresentationStyle > actually vending a presentation controller for the style
- Alerts: _UIAlertControllerAlertPResentationController
- ActionSheet (iphone): _UIAlertControllerActionSheetCompactPC
- ActionSheet(ipad): _UIAlertControllerActionSheetRegularPC

## Presenting
- presentVC 
- pushVC
- showVC (adaptive, mostly used for container VC, e.g: SplitVC)
- showDetailVC (adaptive, mostly used for container VC, e.g: SplitVC)

## Special Presentation
- UIAlertController
- UISearchController
- UIPopoverPresentationController > the only custom presentation ctrl publicly available in UIKit

## Custom Presentation Controller

### 1. Subclass UIPresentationController
1. Transitioning and Chrome
  * presentationTransitionWillBegin()
  * dismissalTransitionWillBegin()
2. Positioning
  * sizeForChildContentContainer(child, withParentContainerSize:) -> CGSize
  * frameOfPresentedViewInContainerView()
3. Adaptivity
  * adaptivePresentationStyle() -> UIModalPresentationStyle > weird that we cannot provide our own presentation style
  * shouldPresentInFullscreen() -> Bool
  * containerViewWillLayoutSubviews() -> used for fine grained control

### 2. Vend Controller
1. UIViewControllerTransitioningDelegate
  * presentingVC conforms to delegate
  * set delegate on presented VC