[Objective-C] memory management of the OC midpoint syntax

Next, let's take a look at the memory management of some syntaxes. (1) Assignment   Assign: direct value assignment, default Retain: Reserved object Copy: copy object Sample Code: @ Property (assign) Person * person; @ Synthesize person = _ person; When using retain: -(Void) setPerson :( Person *) person { if(_person!=person){ [_person release]; _person=[person retain]; }} When using copy (the object must implement the copy Protocol)   -(void)setPerson:(Person *)person{ if(_person!=person){ [_person release]; _person=[person copy]; }} (2): read/write       Readwrite: generate the getter and setter methods. The default value is Readonly: generate the getter Method Sample Code: -(Void) setPerson :( Person *) person { @ Synchronized (self) {_ person = person ;}// setting method   (3) atomicity   Atomic: thread protection exists in a multi-threaded environment. The default value is Noatomic: There is no thread protection in a multi-threaded environment. Sample Code: -(Person *) person { @synchronized(self){ return _person; } }     Differences: Assign: assign values directly, just an alias. Retain: Keep this object. The two objects point to the same location. Copy: opens up a new memory space, pointing to different memory locations, the reference count is 1, However, it has nothing to do with the previous object (except in special cases)