Api :: V1 :: ApiController is created using namespaces in rails.
I am trying to read the model with api and return the response.

Error message

As an error, if you try to operate a model in the Controller, Api :: V1 :: is automatically added to the beginning of the specified model and an uninitialize constant error occurs.
(The following is the case of Social :: User.find)

uninitialized constant Api :: V1 :: Social :: User
Applicable source code
# api/v1/api_controller.rb
class Api :: V1 :: ApiController<ActionController :: Api
Def test
User = Social :: User.find 1
Render status: 200, json: {name: user.name}
# config/routes.rb
namespace: api, {format: 'json'} do
  namespace: v1 do
      get 'api_test', to: 'api # test'
# social/user.rb
module Social
  class User<ApplicationRecord

The model can be operated on the rails console without any problems.
The phenomenon that the above namespace is given only by operation from the controller has occurred.

user = Social :: User.find 1
Supplemental information (FW/tool version etc.)

rails 5.2.0
ruby 2.2.7