Design pattern. Policy object

Policy it's a business logic. So we need to incapsulate it.

class UsersController < ApplicationController
  class ProjectsController < ApplicationController
   def create
     if can_create_project?
       @project = Project.create!(project_params)
       render json: @project, status: :created
     else
       head :unauthorized
     end
   end

  private

  def can_create_project?
     current_user.manager? &&
       current_user.projects.count < Project.max_count &&
       redis.get('projects_creation_blocked') != '1'
   end

  def project_params
     params.require(:project).permit(:name, :description)
   end

  def redis
      Redis.current
    end
  end

  def User < ActiveRecord::Base
     enum role: [:manager, :employee, :guest]
  end

We create new class with policies.

class CreateProjectPolicy
  def initialize(user, redis_client)
    @user = user
    @redis_client = redis_client
  end

  def allowed?
    @user.manager? && below_project_limit && !project_creation_blocked
  end

 private

  def below_project_limit
    @user.projects.count < Project.max_count
  end

  def project_creation_blocked
    @redis_client.get('projects_creation_blocked') == '1'
  end
end

class ProjectsController < ApplicationController
  def create
    if policy.allowed?
       @project = Project.create!(project_params)
       render json: @project, status: :created
     else
       head :unauthorized
     end
  end

  private

  def project_params
     params.require(:project).permit(:name, :description)
  end

  def policy
     CreateProjectPolicy.new(current_user, redis)
  end

  def redis
     Redis.current
  end
end

def User < ActiveRecord::Base
   enum role: [:manager, :employee, :guest]
end

(c) https://www.sitepoint.com/7-design-patterns-to-refactor-mvc-components-in-rails/