Meta-programming Method to find the resource for controllers

MetaprogrammingFindResourse.rb

class ApplicationController < ActionController::Base

  %w(user category post comment).each do |name|
    define_method "find_#{name}" do
      obj = instance_variable_set("@#{name}", name.camelize.constantize.find_by_id(params[:id]))
      unless obj
        flash[:alert] = "#{name.camelize} not found"
        respond_to do |format|
          format.html{ redirect_to "/#{name.pluralize}" }
          format.js{ render js: "window.location='/#{name.pluralize}'" }
        end
      end
    end
  end

end

class UsersController < ApplicationController
  before_action :find_user, only: [:show, :edit, :update, :destroy]
end

class CategoriesController < ApplicationController
  before_action :find_category, only: [:show, :edit, :update, :destroy]
end

class PostsController < ApplicationController
  before_action :find_post, only: [:show, :edit, :update, :destroy]
end

class CommentController < ApplicationController
  before_action :find_Comment, only: [:show, :edit, :update, :destroy]
end