Cocos2dx reference count

A class, new or create. The reference count is 1,

If the reference count is 0, the Destructor is called.

If the delete class pointer is used, the Destructor is also called.

If a Class A's pointer is held by multiple classes, let a inherit from ref, and when each class holds a's reference, retain, and release if not needed

Cc_safe_release_null will release, and then let the pointer point to nullptr. If you change the pointer to (such as = nullptr, = NULL), The Destructor will not be called.