Question

I need to know if the retaincount of objects should always be 0 if i want to have a good memory management in my code. I got the following code from a book. and there’s a statement NSLog called after release = 2, So should i have to release it 2 more times so that the retaincount will be 0 ?

#import <Foundation/NSObject.h>
    #import <Foundation/NSAutoreleasePool.h>
   #import <Foundation/NSString.h>
 #import <Foundation/NSArray.h>
 #import <Foundation/NSValue.h>
 int main (int argc, char *argv[])
 {
 NSAutoreleasePool * pool = [[NSAutoreleasePool alloc] init];
 NSNumber *myInt = [NSNumber numberWithInteger: 100];
 NSNumber *myInt2;
 NSMutableArray *myArr = [NSMutableArray array];
 NSLog (@”myInt retain count = %lx”,
 (unsigned long) [myInt retainCount]);
 [myArr addObject: myInt];
 NSLog (@”after adding to array = %lx”,
 (unsigned long) [myInt retainCount]);
 myInt2 = myInt;
 NSLog (@”after asssignment to myInt2 = %lx”,
 (unsigned long) [myInt retainCount]);
 [myInt retain];
 NSLog (@”myInt after retain = %lx”,
 (unsigned long) [myInt retainCount]);


 NSLog (@”myInt2 after retain = %lx”,
 (unsigned long) [myInt2 retainCount]);
 [myInt release];
 NSLog (@”after release = %lx”,
 (unsigned long) [myInt retainCount]);
 [myArr removeObjectAtIndex: 0];
 NSLog (@”after removal from array = %lx”,
 (unsigned long) [myInt retainCount]);
 [pool drain];
 return 0;
 }

Program Output

myInt retain count = 1
after adding to array = 2
after asssignment to myInt2 = 2
myInt after retain = 3
myInt2 after retain = 3
after release = 2
after removal from array = 1

UPDATE

The following code was taken from the Apples memory management document. They have retained a NSNumber object and its never been released, is this OK ?

- (void)setCount:(NSNumber *)newCount {
[newCount retain];
[_count release];
// Make the new assignment.
_count = newCount;
}

Answer 1

You shouldn’t be worried about the retain count of your objects, especially because the the NSArray or other objects might retain and then only later release things you pass to them. I’d strongly suggest focusing instead on Objective-C and Cocoa’s memory management rules, which ensure that things are cleaned up when needed.