Question

1.Assignment

NSArray* a = xxxxxx;

NSArray* b;

b = a;

2.Copy

NSArray* a = xxxxxx;

NSArray* b;

b = [a copy];

I know copy is “light copy”,mutable copy is “deep copy”.

copy is copy memory address,and mutable copy is copy memory objects.

But i don’t know assignment and copy’s different.

It’s the same?

Answer 1

This Apple documentation is helpful:

The normal copy is a shallow copy that produces a new collection that
shares ownership of the objects with the original. Deep copies create
new objects from the originals and add those to the new collection.

Therefore, in your first example, b points to the same NSArray instance as a. In the second example, b points to a new instance of NSArray containing references to the same objects contained in the array pointed to by a.