TransitionController specification

Discussion thread	Status
	Drafting as of Oct 25, 2016

This is the engineering specification for the TransitionController object.

Overview

TransitionController is a bridge between the platform's transitioning architecture and a TransitionDirector.

MVP

Concrete type: A TransitionController is a concrete type.

Example pseudo-code:

TransitionController {
}

One transition controller per view controller: Every view controller stores its own weakly-created TransitionController instance.

directorClass API: Provide an API for storing a TransitionDirector type.

The type must represent an object that conforms to the TransitionDirector type.

Example pseudo-code:

TransitionController {
  public var directorClass: TransitionDirector.type

Transition will start: The following should occur when a transition is about to begin:

1. Initialize the director
2. Invoke the setUp event on the director
3. Commit the setUp transaction to a runtime

Example pseudo-code:

TransitionController {
  function transitionWillStart(initialDirection) {
    let runtime = Runtime()
    runtime.delegate = self
    let transition = Transition(...)
    director = directorClass(transition)
  }
}

Finish on idle: Finish the transition when the runtime enters the idle activity state.

Open Questions

• How do we handle directors that never enter the .Active state?