Cocos2d: Stick two CCSprite?

I am trying to superimpose sprites by drag and drop and when to sprites collide I want to stick them so if one fall the other sprite stack on it will fall two. Any ideas please?

Best regards

For more precision I need help on the stick part. Thanks

Solution

I'd follow these steps.-

Extend CCSprite to add a property CCSprite *spriteToFollow
You should also add a CGPoint to store the offset between two sprites when they collide.
Once one CustomSprite collides with another one, set the proper spriteToFollow
On CustomSprite init method, call to scheduleUpdate
On update method, if spriteToFollow exists, update the current to spriteToFollow.position + offset

Hope it helps.