objective c - release problem

Question

Possible Duplicate:
NSNumber retain count issue

Hello, I have the following code:

 NSNumber *number = [NSNumber numberWithInt:5];
 int i = [number retainCount];
 [number release];
 i = [number retainCount];
        [number release];
        i = [number retainCount];

the problem is that in line 2 , the value of parameter i is 2 and in line 4 the value is 1. then in line 6 the value is still 1.????????

first i dont understand why after init *number the retaincount is 2 and not 1?? second i dont understand why after release it 2 times retaincount is not 0? it doesnt matter how many times i release the object the retaincount stay 1.

Answer 1

The problem is that you should never look at the 'retainCount' of an object unless you really know what you're doing, it'll only confuse you.

What's going on is that NSNumber is doing something behind the scenes. I'm not sure what, and I usually don't care. If I create an abject, I'm responsible for releasing it. As long as I fulfill my responsibilities, everything will work out as it should.

In your specific example, you're getting a reference to an 'NSNumber' and releasing it twice. Since you don't own that object, you should not be releasing it at all.

---

To clarify, the reason you shouldn't be looking at retain counts is that it frequently will mislead you. To quote @chuck from the link in the comments.

If you suspect you have a leak, you should check with the real debugging tools meant for that purpose, not by poking at retain counts. And for code you're writing, you should primarily be concerned with following the guidelines I linked above.

Answer 2

the same in this code

look at object range first i alloc the object (i believe the ref count is 1) then in the end i release it (i think the ref count need to be zero) so how the line : int i = [range intValue]; , is working?? by this time the range object need to be deallocated because previous line was released the object . i assumed that line int i = [range intValue]; was need to fail.

what i am missing?

-(NSString*)ParseLocationToString { NSNumber *range; NSString *locationAsString; locationAsString = [[NSString alloc] init];

locationAsString = m_Latitude;
locationAsString = [locationAsString stringByAppendingString:@","];
locationAsString = [locationAsString stringByAppendingString:m_Longtitude];
locationAsString = [locationAsString stringByAppendingString:@","];
range = [[NSNumber alloc] initWithInteger:m_RangeForResult];
locationAsString = [locationAsString stringByAppendingString:[range stringValue]];

[range release];
int i = [range intValue];

return locationAsString;

}

Answer 3

so generaly the steps that increment the retain counter are:

1. i used alloc.

2. i used property that have the retain attribute.

3. every initWith*** function ?????(i am not sure)

how do i know if frame work built in function that returns objects (for example stringByAppndString , numberWithDoble , etc... ) were return new object with retainCount = 1 , so i need to remember to release ?.

I am looking for few basic guidance to when i need to use release.

thanks