为什么80%的码农都做不了架构师？>>> 
方法一：在dealloc里面书写监听事件，因为只有pop才会调用dealloc，push不会掉用
- (void)dealloc {
YLLog(@"123");
}
方法二：在- (void)viewWillDisappear:(BOOL)animated中调用
- (void)viewWillDisappear:(BOOL)animated{
if ([self.navigationController.viewControllers indexOfObject:self]==NSNotFound) {
NSLog(@"clicked navigationbar back button");
}
}
方法三：重写返回按钮，然后调用返回按钮的方法即可：如
- (void)popViewcontrollerFunc {
UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"" message:@"确定要放弃到手的奖品吗" delegate:self cancelButtonTitle:@"点错啦" otherButtonTitles:@"狠心放弃", nil];
alert.tag = 10001;
[alert show];
}