Non-Standard ApplicationPolicy for Pundit

application_policy.rb

# Handling Application rights thanks to roles
#
# A direct adaptation of http://through-voidness.blogspot.fr/2013/10/advanced-rails-4-authorization-with.html
# but much more performance-wise
class ApplicationPolicy
  attr_reader :user, :record

  def initialize(user, record)
    raise Pundit::NotAuthorizedError, 'Must be signed in.' unless user
    @user = user
    @record = record
  end

  ##############################################################
  # Globalizing policies handling based on the role activities #
  ##############################################################

  # @return [Array] list of all users allowed activities
  def user_activities
    @user.roles.pluck(:activities).flatten.uniq
  end

  # @param [Symbol] method Method to check in class
  # @return [String] A combination of model and method
  # @note We allow only Class or Symbol, nothing else, to do things like `authorize :dashboard` or `authorize Product`
  def inferred_activity(method)
    record_class = (@record.class == Class || @record.class == Symbol) ? @record.to_s : @record.class.name
    "#{record_class.downcase}:#{method}"
  end

  # @param [String] name method name
  # @param [Object] args method args
  def method_missing(name, *args)
    method_name = name.to_s
    if method_name[-1..-1] == '?'
      user_activities.include?(inferred_activity(method_name[0..-2]))
    else
      super
    end
  end

  ##########################
  # Keeping some shortcuts #
  ##########################

  # Just a shortcut for create?
  def new?
    create?
  end

  # Just a shortcut for edit?
  def edit?
    update?
  end

  ##################
  # Scope handling #
  ##################

  def scope
    Pundit.policy_scope!(user, record.class)
  end

  class Scope
    attr_reader :user, :scope

    def initialize(user, scope)
      @user = user
      @scope = scope
    end

    def resolve
      scope
    end
  end
end