Defining Pundit policies using role objects

roles.rb

class Role
  def can?(ability)
    ability_query = "can_#{ability}?"
    respond_to?(ability_query) ? __send__(ability_query) : false
  end
end

class ManagerRole < Role
  def can_manage_users?
    true
  end
end

class StaffRole < Role
  def can_manage_users?
    false
  end
end

class User
  def roles
    [ManagerRole.new, StaffRole.new]
  end
  
  def can?(ability)
    roles.any? { |r| r.can?(ability) }
  end
end

class UserPolicy < ApplicationPolicy
  def create?
    user.can?(:manage_users) 
  end
end