Codeigniter路由在某些情况下不起作用?

I got used to use Grocery CRUD library which eases CRUD process. When I'm going to use the edit process, The URI is would be some thing like http://www.example.com/users/get_users/edit/userID(num). The issue is, If one of the users removes the userID this will gives an error due to the required parameter by edit method, So that I have tried to use Codeigniter routing as below

$route['users/get_users/edit'] = "users/get_users";

But this didn't work..!

Any idea please...

$route['users/get_users/edit/:num'] = "users/get_users"; 

It should be like this. And I think you getting error message because "users/get_users" still expects userID. Its better to come up with the error message as well.