iOS5中的viewController对象BAD_ACCESS？

Question

Usually when we push viewcontroller, we will create object for view controller, after that line we will push and release it.
But it gets crashed when we run in iOS5. So I retained the object through propery and declare it in interface as global. Now it is working fine. Will retaining viewcontroller occupy much memory? What is the difference between following two approches?

One:

MyViewCOntroller *obj = [[MyViewCOntroller  alloc] init];
[self.navigationController pushViewController:obj Animated:YES];
[obj Release]

Two:

self.obj = [[MyViewCOntroller  alloc] init];
[self.navigationController pushViewController:self.obj Animated:YES];
[self.obj Release]

Answer 1

The first one should be right and please detect for the crash reason again. It can't be crashed when you use the first one to push a new view controller.

As for the difference: in the second one, if you declare the obj as a var of self class and you don't use ARC , you take care of obj like the other instance vars. You just need to do release in the dealloc .

Answer 2

Generally speaking, you should not release property (self.obj) in methods except for dealloc .
The second code snippet should be replaced like this:

self.obj = [[MyViewCOntroller alloc] init];
[self.navigationController pushViewController:self.obj Animated:YES];

And add below one to your dealloc method:

self.obj = nil; // Property will release itself and set the point to nil

The first code snippet is OK, you alloced local instance and released it after used.

Answer 3

why aren't you init your view controller with nib?

    SearchView *secondViewController = [[SearchView alloc] initWithNibName:@"SearchView" bundle:nil];
    [self.navigationController pushViewController:secondViewController animated:YES];
    [secondViewController release];

be careful with retaining any objects. You must be completely sure that you init it only onse and then release it. If you do so, you may not care about memory. The difference between your inits is: in 1st case you creating ner object. It is NOT retain, but, may be leak, I'm not shure. I think you should add autorelease . In 2nd case you have an object's property (probebly, retain?) in header. you must release it in dealloc method

Answer 4

Are you passing the View Controller to the new Object? If yes, Are you releasing this View Controller property in the new View Controller's dealloc method? That would be a double release. Example no. 2 would solve this problem because of the (retain) type property it may have in the old View Controller, would set its retain count to 2.