iPhone development: How to Catch Exception/NSError in Objective-C?

I want my application to never just crash stupidly. I know that code quality is the root solution for this. But I still need an application to never crash when some unexpected bug happens. Here is code I want to try.

-(void)testException
{
    @try
    {
        NSString* str;
        [str release];
    }
    @catch(NSException* ex)
    {
        NSLog(@"Bug captured");
    }
}

I know this one does not work. Because release never raise an exception. Here are my questions:

1. How to reach this kind of objective, bug will be captured, no crash?
2. How do I know which system library will raise exception and so I can write some code and know it works?

Here's what I have read

• a. Exception Programming Topics for Cocoa
• b. Error Handling Programming
  Guide For Cocoa

I come from an experienced Microsoft programmer background in which catch exception or unexpected exception always prevent my program from crashing in a very bad environment.

How did you guys/gals (Mac genius programmers) make crash free programs happened? Share your experience.