＊ When you create an object using new, alloc, or copy, the object has a retain count of 1. You are responsible for sending the object a release or autorelease message when you’re done with it. That way, it gets cleaned up when its useful life is over.
* When you get hold of an object via any other mechanism, assume it has a retain count of 1 and that it has already been autoreleased. You don’t need to do any fur- ther work to make sure it gets cleaned up. If you’re going to hang on to the object for any length of time, retain it and make sure to release it when you’re done.
* If you retain an object, you need to (eventually) release or autorelease it. Balance these retains and releases. (查看原文)
* If you access an instance variable by reference, self (the objective performing the method) is retained.
* If you access an instance variable by value, the variable by value, the variable is retained. (查看原文)
