title: How do you stop a particle effect? (SKEmitterNode)
body: <p>I currently have this code in a collide statement where if collide with object then this particle happens but how do I stop it? As it goes on forever whereas I only want to happen a couple of times per contactetc</p>
  
  <pre><code>SKEmitterNode *emitter =  [NSKeyedUnarchiver unarchiveObjectWithFile:[[NSBundle mainBundle]     pathForResource:@"ff" ofType:@"sks"]];
  emitter.zPosition = 0;
  emitter.particlePositionRange = CGVectorMake(0, self.size.height);
  emitter.position = CGPointMake(self.size.width, self.size.height/2);
  [self addChild:emitter];
  </code></pre>