Ivar - Retain, Assign and Release related crash

[raven]

This is probably more a conceptual issues so experienced insight is welcome.

localWindow = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
self.window = localWindow;
[localWindow release];
/* Now the following code crashes
localTBC = [[UITabBarController alloc] init];
tabBarController = localTBC;
[localTBC release];
*/
tabBarController = [[UITabBarController alloc] init]; //this works great

***
@property (nonatomic, retain) UIWindow *window;
@property (nonatomic, retain) UITabBarController *tabBarController;
***


Why does it crash when I use the commented lines for tabBarController for the following line.

tabBarController.viewControllers = theVCArray;

It crash as tabBarController has already been released in the commented code case.

I assume the retain count will be 2 due to the assign and retain on tabBarController ivar as it will be for window ivar. Why is it okay with window but not with tabBarController ?

[Kalimba]

Originally Posted by raven

This is probably more a conceptual issues so experienced insight is welcome.

      localWindow = [[UIWindow alloc] initWithFrame:[[UIScreen      mainScreen] bounds]];
	self.window = localWindow;
	[localWindow release];
	/*  Now the following code crashes
	localTBC = [[UITabBarController alloc] init];
	tabBarController = localTBC;
	[localTBC release];
	*/
	tabBarController = [[UITabBarController alloc] init]; //this works great

***
@property (nonatomic, retain) UIWindow *window;
@property (nonatomic, retain) UITabBarController *tabBarController;
***


Why does it crash when I use the commented lines for tabBarController for the following line.

tabBarController.viewControllers = theVCArray;

It crash as tabBarController has already been released in the commented code case.

I assume the retain count will be 2 due to the assign and retain on tabBarController ivar as it will be for window ivar. Why is it okay with window but not with tabBarController ?

It's crashing at that line because the "tabBarController" isn't pointing to anything valid, as you've released the instance you had allocated.

	tabBarController = localTBC;

should be this:

	self.tabBarController = localTBC;

[raven]

But aren't these two lines the same ?

You are using the dot notation but in both cases we are referring to the same ivar called tabBarController !

[ftm]

Are you also doing an

@synthesize tabBarController;

in your class?

My understanding is that synthesize is what makes the created getters and setters actually do the retain and release code correctly.

[smasher]

Originally Posted by raven

But aren't these two lines the same ?

You are using the dot notation but in both cases we are referring to the same ivar called tabBarController !

Dot notation doesn't access the ivar directly - it calls the methods tabBarController and setTabBarController. Those methods handle the reatain and release, and it's "@synthesize tabBarController;" that creates these methods.