请高手分析一下ios的内存管理

jackeyj

1. 
   
2. - (IBAction)butonPressed:(id)sender
   
3. {
   
4.         NSInteger stateRow = [picker selectedRowInComponent:kStateComponent];
   
5.         NSInteger zipRow = [picker selectedRowInComponent:kZipComponent];
   
6.        
   
7.         NSString *state = [self.states objectAtIndex:stateRow];
   
8.         NSString *zip = [self.zips objectAtIndex:zipRow];
   
9.        
   
10.         NSString *title = [[NSString alloc] initWithFormat:@"You selected zip code %@.", zip];
    
11.         NSString *message = [[NSString alloc] initWithFormat:@"%@ is in %@", zip, state];
    
12.        
    
13.         UIAlertView *alert = [[UIAlertView alloc] initWithTitle:title message:message delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
    
14.         [alert show];
    
15.         [alert release];
    
16.         [title release];
    
17.         [message release];
    
18.        NSLog(@"-----> %@", title);//还是可以访问到，why？？
    
19. }
    

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为什么release后的对象还能够访问，既然这样又何必release 呢？