Objective-C Moving Items Between Arrays (Memory Management)

Question

Is there any practical difference between the following two code snippets:

NSObject * obj = [[_mutableArrayOne objectAtIndex:i] retain];
[_mutableArrayOne removeObject:obj];
[_mutableArrayTwo addObject:obj];
[obj release];

and

NSObject * obj = [_mutableArrayOne objectAtIndex:i];
[_mutableArrayTwo addObject:obj];
[_mutableArrayOne removeObject:obj];

Answer 1

Only the extra retain/release cycle that you ask it to do.

It might have some performance impact inside a loop of time-sensitive processing?

Answer 2

Other than the need to call retain and release twice instead of once, no. The end result is the same.

Answer 3

If you want to own the object in the index 'i' then remove object from array and then you can add it back to the array in the later stage of the project.

I suggest option 2 should be careful : the object will not be in the array any more.

The result is different -- Option 1 you will have the 'object' in mutable array and in option 2 'object' will not be in array (removeObject remove all occurrences)

Answer 4

Both are same with respect to Memory Management and programming logic. Only in the first case you have to operate a pair of extra retain/release operation.