Retain / Release - Reference Count

Question

Please kindly point out what is wrong in my code. I define a variable idleTimer of my custom type

@property (nonatomic, retain) IdleTimer *idleTimer;

Then when I run the following codes, it crashes.

IdleTimer   *idleTimerTemp  =   [[IdleTimer alloc] initTimer:PERIOD_COUPON_POPUP];
idleTimer   = idleTimerTemp;

NSLog(@"Pt. 1 %d %d", [idleTimerTemp retainCount], [idleTimer retainCount]);

[idleTimer setDelegate:self];
[idleTimerTemp release];
NSLog(@"Pt. 2 %d %d", [idleTimerTemp retainCount], [idleTimer retainCount]);

If the idleTimer is used again, it crashes.

But it I retain the idleTimerTemp on "idleTimer = idleTimerTemp". No crash at all.

But my variable is defined as retain. what is wrong ?

As a side note, [-retainCount is not all that useful](http://stackoverflow.com/questions/4636146/when-to-use-retaincount/4636477#4636477). — Brad Larson, Oct 23 '11 at 19:11

score 2 · Answer 1 · answered Oct 23 '11 at 07:39

2

You're assigning to the idleTimer ivar directly instead of using the accessors. Do this instead:

self.idleTimer = idleTimerTemp;

The property accessors can't implement the semantics you specify if you don't use them.

answered Oct 23 '11 at 07:39

Caleb

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Think about it this way: `self.idletimer=X` is shorthand for `[self setIdleTimer:X]` (with type checking). – titaniumdecoy Oct 23 '11 at 07:43

score 2 · Accepted Answer · answered Oct 23 '11 at 07:43

2

Your property is defined as retain but that doesn't do anything with respect to the instance variable which is the backing storage for the property. Presumably somewhere in your code, you've done an @synthesize idleTimer;. That creates an accessor pair which implements the memory management you requested.

The only way to get that behavior is to call the accessor itself. So if you assign directly to idleTimer, that does nothing, but if you use self.idleTimer = idleTimerTemp, then the -setIdleTimer: accessor gets called, which will retain the parameter.

answered Oct 23 '11 at 07:43

Chris Parker

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So, is it a correct approach that I don't call [idleTimerTemp release] in this case ? Is it a common practice ? – SkyEagle888 Oct 23 '11 at 08:12
In this case, you'd probably release `idleTimer` in your class's `-dealloc` method. – Chris Parker Oct 25 '11 at 03:55

Retain / Release - Reference Count

2 Answers2