The difference between copy and retain

Copy actually creates an identical object, and retain is not:

such as a NSString object, the address is 0x1111, the content is @ "STR"

Copy to another nsstring, the address is 0x2222, the content is the same, the new object retain is 1, the old object has not changed

Retain to another nsstring, the same address (set up a pointer, pointer copy), the content of course the same, the object's retain value +1

That is, retain is a pointer copy and copy is a copy of the content.

The difference between copy and retain