UINavigationController 默认返回按钮时候 做一些操作

gistfile1.txt

- (void)viewWillDisappear:(BOOL)animated
{
    if ([self.navigationController.viewControllers indexOfObject:self]== NSNotFound) {
        // back button was pressed.  We know this is true because self is no longer
        // in the navigation stack.
        [self setEditMode];
    }
    [super viewWillDisappear:animated];
}