CODEWITHSUNDEEP
iphonememory-managementmethodsmessageretain
dac
dac

Reputation: 55

iphone: which function/method call increases retainCounter? why mem management acting so strange?

hey people, I have a problem with my understanding of the memory management in the iphone.

I have the following strange situation:

            CAGradientLayer * hButtonLayer = [[CAGradientLayer alloc] init];
    NSLog(@"1: retaincounter is?: %d", [hButtonLayer retainCount]);
        [hButtonLayer setBounds:tempButton.bounds];
    NSLog(@"2: retaincounter is?: %d", [hButtonLayer retainCount]);
        [hButtonLayer setColors:[NSArray arrayWithObjects:
                                                        [UIColor colorWithRed:0.2 green:0.3 blue:0.4 alpha:1.0],
                                                        [UIColor colorWithRed:0.4 green:0.5 blue:0.6 alpha:1.0], nil]];
    NSLog(@"3: retaincounter is?: %d", [hButtonLayer retainCount]);
        [[tempButton layer] insertSublayer:hButtonLayer atIndex:0];
    NSLog(@"4: retaincounter is?: %d", [hButtonLayer retainCount]);

the output on the console shows the following:

1: retaincounter is?: 1
2: retaincounter is?: 2
3: retaincounter is?: 2
4: retaincounter is?: 3

ok, at 1) it's clear that the counter equals 1, because the Layer is alloced and initialized. but why is at 2) the "setBounds"-methid increasing the retain counter? and at 3) the retain counter is not increased by the "setColors"-method... and "insertSublayer" is again increasing the retain counter!

why are these methods increasing the counter? how should I know, if some framework-method increases something? I mean, if I decreases the retain counter and some framework-method didn't increase the counter, I will get a crash - how should I determine, if a method increases or not increases the retain counter?

thanks for any help!

Upvotes: 0

Views: 109

Answers (2)

AechoLiu
AechoLiu

Reputation: 18378

As Stephen said, and any container like NSArray, NSDictionary will retain object. The sub views of UIView is maintained by array, so any added sub view will be retained.

The properties of an object, the memory management policy can be found on Apple's document. Or, you can go to the definition of the class and read its declaration.

Upvotes: 0

Stephen Darlington
Stephen Darlington

Reputation: 52565

Don't use the retain count as a debugging aid. Without knowing how system and third party frameworks are implemented you cannot know what the retain count should be.

It's very simple:

  1. If you alloc or copy or retain an object, you "own" it and need to either release or autorelease it at some later point
  2. Otherwise you do not own it and you are not responsible for its memory

Upvotes: 2

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