IOS 设置导航条navigationbar统一返回按钮

//在自定义的navigationController里面重写push方法
- (void)pushViewController:(UIViewController *)viewController animated:(BOOL)animated
{
    
    
    if (self.childViewControllers.count>0) //非根控制器
    {
        viewController.hidesBottomBarWhenPushed = YES;

        viewController.navigationItem.leftBarButtonItem = [UIBarButtonItem backItemWithImage:[UIImage imageNamed:@"imageName"] hightImage:[UIImage imageNamed:@"imageName"] target:self action:@selector(back) title:@"返回"];
    }
    [super pushViewController:viewController animated:YES];
}

- (void)back
{
    [self popViewControllerAnimated:YES];
}