objective-c - iOS 深浅拷贝？

Question

NSString *i = @"1";
NSString *j = [i mutableCopy];
NSLog(@"i=%p,j=%p",i,j);

打印地址不一样，由此可见是内容拷贝
继续
i = @"2";
NSLog(@"i=%@,j=%@",i,j);
那么问题来了，为什么j的值还是1？

Answer 1

Content copy is a deep copy. The new j generated is a new object and has nothing to do with i. So changing i will not affect j.

Answer 2

The addresses are different, which means they are two objects. So the question is, why are the values ​​​​between two independent objects still related?

Answer 3

ok, let me check the information first