Memory management in objective c arrays

For this question:

Test *t1 = [[Test alloc]init];
Test *t2 = [Test new];
Test *t3 = [t1 copy];

NSLog(@"Retain count of Object 1 : %ld",[t1 retainCount]);
NSLog(@"Retain count of Object 2 : %ld",[t2 retainCount]);
NSLog(@"Retain count of Object 3 : %ld",[t3 retainCount]);

NSArray *arr = @[t1,t2,t3];

NSLog(@"Retain count of Object 1 : %ld",[t1 retainCount]);
NSLog(@"Retain count of Object 2 : %ld",[t2 retainCount]);
NSLog(@"Retain count of Object 3 : %ld",[t3 retainCount]);

The answer is:

Retain count of Object 1 : 1
Retain count of Object 2 : 1
Retain count of Object 3 : 1
Retain count of Object 1 : 3
Retain count of Object 2 : 2
Retain count of Object 3 : 3

I can understand that adding an object to an array increases its reference count by 1, but for objects 1 & 3 it increases by 2?? Can someone answer this?

From what you have shown (which doesn't show how the class is implemented), here is a guess:

• Your Test class's copyWithZone: method returns the receiver object itself, without retaining. (Which by the way is a violation of the memory management rules, which says that a method starting with copy must return an owning (retained) instance. A class's copy is allowed to return the object itself or a new object, but in both cases it must retain it.)
• Therefore, t1 and t3 point to the same object, which only has 1 retain count, when the object was created. (Since the copy incorrectly didn't retain.)
• When you put elements into an array, the array retains each element. So the object pointed to by t2 gets retained once, getting a retain count of 2, and the object pointed to by t1 and t3 gets retained twice, getting a retain count of 3.