Sources

A source turns an Interaction into a MotionObservable stream.

Types

There are four primary types of sources:

• Gestures
• Scroll views
• Springs
• Tweens

All sources have the same essential API shape. In Swift:

func sourceToStream(Source<T>) -> MotionObservable<T>

In Java:

Source.from(source) // Returns a MotionObservable

Output types

Gesture recognizers are expected to emit themselves whenever the gesture’s state is modified.

Scroll views are expected to emit content offset as a Point type.

Springs and Tweens are expected to support emitting any T value type.

Connection shapes

There are at least two distinct MotionObservable connection shapes: inline and object.

Inline connections

This type of source is able to make use of inline function APIs.

func springToStream(spring: Spring<T>) -> MotionObservable<T> {
  return MotionObservable { observer in
    ... // Configure the spring source

    springSource.start()

    return {
      springSource.stop()
    }
  }
}

Object connections

Consider the following example of a gestureToStream that we might make on iOS:

func gestureToStream(_ gesture: UIGestureRecognizer) -> MotionObservable<UIGestureRecognizer> {
  return MotionObservable { observer in
    let connection = GestureConnection(subscribedTo: gesture, observer: observer)
    return {
      connection.disconnect()
    }
  }
}

Our gesture recognizer requires an object that can receive target/action events, so we define a GestureConnection object that receives these events.