title: Custom easing action with Cocos2D-iphone
body: <p>How would one go about creating a custom action in Cocos2D that was able to perform a 'callback' over time, making each call to the callback progressively longer than the last call to it (using something similar to the EaseExponentialOut action already provided with Cocos2D.</p>
  
  <p>Something similar to this: (which does not work)</p>
  
  <pre><code>id sequence = [Sequence actions: [CallFunc actionWithTarget: self selector: @selector(spinTick)], [DelayTime actionWithDuration: 0.034f], nil];
  id repeat = [Repeat actionWithAction: [sequence copy]  times: 18];
  id ease = [EaseExponentialOut actionWithAction: [repeat copy]];
  [ease setDuration:4];
  
  id play = [CallFunc actionWithTarget:self selector:@selector(play)];
  [self runAction: [Sequence actions: [ease copy], [play copy], nil]];
  </code></pre>
  
  <p>The above code executes the entire 'sequence', 18 times and then executes the 'play' callback at the end of the last sequence.</p>
  
  <p>However, the EaseExponentialOut does not appear to have any affect at all on the 'repeat' action that is created - I had expected it to adjust the duration of the 'DelayTime' action inside of the 'sequence' action, but it does not appear to do this.</p>
  
  <p>I also attempted to create my own custom action based on IntervalAction, but failed miserably.</p>