解决方法
我花了很多考验,提出了一个几乎“优雅”的解决方案：
scope "/users/:key1/:key2" do
resource :users,:path => "" do
resources :posts
end
end
它产生：
users_posts GET /users/:key1/:key2/posts(.:format) posts#index
POST /users/:key1/:key2/posts(.:format) posts#create
new_users_post GET /users/:key1/:key2/posts/new(.:format) posts#new
edit_users_post GET /users/:key1/:key2/posts/:id/edit(.:format) posts#edit
users_post GET /users/:key1/:key2/posts/:id(.:format) posts#show
PUT /users/:key1/:key2/posts/:id(.:format) posts#update
DELETE /users/:key1/:key2/posts/:id(.:format) posts#destroy
users POST /users/:key1/:key2(.:format) users#create
new_users GET /users/:key1/:key2/new(.:format) users#new
edit_users GET /users/:key1/:key2/edit(.:format) users#edit
GET /users/:key1/:key2(.:format) users#show
PUT /users/:key1/:key2(.:format) users#update
DELETE /users/:key1/:key2(.:format) users#destroy