application crashed after dismiss presentModalViewController - iphone

Question

i have a problem when going to another controller with the following buttons
-(IBAction)art:(id)sender{
TestYourInfoViewController *test = [[TestYourInfoViewController alloc]
initWithNibName:#"TestYourInfoViewController" bundle:[NSBundle mainBundle]];
test.questionType = #"art";
testYourInfoViewC = test;
[testYourInfoViewC setModalTransitionStyle:UIModalTransitionStyleFlipHorizontal];
[self.navigationController presentModalViewController:testYourInfoViewC animated:YES ];
[test release];
}
and when i go back with the following
-(IBAction)back:(id)sender{
[[self parentViewController] dismissModalViewControllerAnimated:YES];
}
it crash the application with no stacktrace.. what is the wrong with that please.

Answer 1

Is testYourInfoViewC defined in the header as a retained #property? If so, you should always be referring to it using self and dot notation.
- (IBAction)art:(id)sender
{
TestYourInfoViewController *test = [[TestYourInfoViewController alloc]
initWithNibName:#"TestYourInfoViewController" bundle:[NSBundle mainBundle]];
test.questionType = #"art";
self.testYourInfoViewC = test;
[self.testYourInfoViewC setModalTransitionStyle:UIModalTransitionStyleFlipHorizontal];
[self.navigationController presentModalViewController:self.testYourInfoViewC animated:YES ];
[test release];
}
When you create a retained #property and #synthesize it, a setter is being created that handles the memory management involved in retaining the new object and releasing the old, but by assigning test to testYourInfoViewC you're bypassing that synthesized setter.
Let's step through this here. You've created test using alloc/init, thus setting its retainCount to 1. Next you've assigned testYourInfoViewC to test. No change in the retain count, testYourInfoViewC is now simply pointing to the same object as test instead of retaining a copy for itself.
Now when you call release on test that retain count returns to 0 and the object is deallocated. Your instance of TestYourInfoViewController is completely gone and testYourInfoViewC is now left flapping in the wind. When attempting to dismiss it, the parentViewController is going to attempt to send some messages to that object behind the scenes, like -viewWillDisappear:, -viewDidDisappear: etc.
Edit: Here's how I handle this kind of situation in my projects. I override the getter for the property and determine whether it needs to be created or not. This way I can call the property anywhere in my code and I can be assured that if its not created it will be allocated, initialized and setup just in time.
- (TestYourInfoViewController *)testYourInfoViewC
{
if (!testYourInfoViewC)
{
testYourInfoViewC = [[TestYourInfoViewController alloc] init]; // This will work because the .xib and class name are identical.
[testYourInfoViewC setModalTransitionStyle:UIModalTransitionStyleFlipHorizontal];
}
return testYourInfoViewC;
}
After you've setup the getter to provide lazy instantiation, your -art: method will look like this...
- (IBAction)art:(id)sender
{
[self.navigationController presentModalViewController:self.testYourInfoViewC animated:YES];
}