Presenters

collection_presenter.rb

class CollectionPresenter
  include Enumerable

  delegate :current_page, :total_pages, :limit_value, :entry_name, :total_count,
    :offset_value, :last_page?, to: :@collection

  cattr_accessor :presenter
  self.presenter = ModelPresenter

  def initialize(collection)
    @collection = collection
  end

  def each(*args, &block)
    @collection.each { |item| yield(presenter.new(item)) }
  end
end

model_presenter.rb

class ModelPresenter
  delegate :to_model, :to_key, :to_param, :to_partial_path, to: :@record

  def initialize(record)
    @record = record
  end
end

user_presenter.rb

class UserPresenter < ModelPresenter
  delegate :email, :full_name, to: :@record

  def full_name_with_email
    "#{@record.full_name} (#{@record.email})"
  end
end

users_presenter.rb

class UsersPresenter < CollectionPresenter
  self.presenter = UserPresenter

  def avarage_something
    @collection.sum(:id) / @collection.size
  end
end