Question about dealloc

[gfxcc]

why you implement dealloc like this?

• (void)dealloc { [self.scrollView removeObserver:self forKeyPath:@"contentOffset"]; [self.scrollView removeObserver:self forKeyPath:@"contentInset"]; self.scrollView = nil; }
• (void)willMoveToSuperview:(UIView *)newSuperview { [super willMoveToSuperview:newSuperview]; if (!newSuperview) { [self.scrollView removeObserver:self forKeyPath:@"contentOffset"]; [self.scrollView removeObserver:self forKeyPath:@"contentInset"]; self.scrollView = nil; } }

why not just removeObserver in (void)willMoveToSuperview like this:

• (void)willMoveToSuperview:(UIView *)newSuperview { [super willMoveToSuperview:newSuperview]; [self.scrollView removeObserver:self forKeyPath:@"contentOffset"]; [self.scrollView removeObserver:self forKeyPath:@"contentInset"]; self.scrollView = nil; }

Another question, when the function dealloc will be called?

Thanks