When we should use pushScene and replaceScene?

I cocos2d, I am using pushScene and replaceScene to move to next scene. But, I am confused which we should use?

When I am using replaceScene in some places app is crashing and giving errors like

-[UITextView length]: unrecognized selector sent to instance 0x842a750  
 Terminating app due t开发者_如何学编程o uncaught exception 'NSInvalidArgumentException', reason: '*** -[UITextView length]: unrecognized selector sent to instance 0x842a750'  

But, in my program I am not passing length to UITextView. My program is in this way

In scene1 I have UITextView, and I am replacing this scene with scene2. Then

-(id)buttonPressed:(id)sender
{
    [description removeFromSuperview];  // It is the textView(description)
    CCScene *Scene = [CCScene node];
    CCLayer *Layer = [scene2 node];

    [Scene addChild:Layer];

    [[CCDirector sharedDirector] setAnimationInterval:1.0/60];
    [[CCDirector sharedDirector] replaceScene: Scene];
}  

But, when I am using pushScene in presence of replaceScene it is working good. Please clarify me which one should use in which cases ?

Thank You

You will want to use replaceScene in almost all cases. The pushScene method keeps the previous scene in memory, which is most likely why its not crashing. Something about that scene isn't quite right and when it deallocates after a replaceScene, the crash occurs. It has nothing to do with cocos2d's replace scene system.

Your UITextView in scene1 is probably released too often. If its created as an autorelease object, don't send it the release message.