先presentModalViewController后pushViewController没有效果的解决方法

本人在做项目的时候，先用presentModalViewController到登录界面，在登录界面在pushViewController到注册界面，push不过去。

LoginViewController *login = [[LoginViewController alloc]init];
[self.navigationController presentModalViewController:login animated:YES];

//在LoginViewController中push到RegisterViewController没有效果
RegisterViewController *registerViewConotroller = [[RegisterViewController alloc]init];
[self.navigationController pushViewController:registerViewConotroller animated:YES];

解决办法，在presentModalViewController的时候加上UINavigationController，就可以了，如下:

LoginViewController *login = [[LoginViewController alloc]init];
UINavigationController *nav = [[UINavigationController alloc]initWithRootViewController:login];
[self.navigationController presentModalViewController:nav animated:YES];