delayBy specification

This is the engineering specification for the MotionObservable operator: delayBy.

Overview

delayBy emits values from upstream after a specified delay amount.

Example usage

stream.delay(by: 0.3)

time  |  upstream  |  downstream
0     |  20        |  
0.1   |            |  
0.2   |  80        |  
0.3   |            |  20
0.4   |            |  
0.5   |            |  80

MVP

Expose a delayBy operator API

Use _nextOperator to implement the operator. Emit values after the specified delay has passed.

class MotionObservable<T> {
  public func delay(by: CGFloat) -> MotionObservable<T>

Cancel the delayed invocation on unsubscription

Unsubscription should cancel any timers that have not yet been fired.