Example of BasePresenter and BaseListPresenter

presenters.rb

# BASE PRESENTERS
class BasePresenter
  def initialize(item)
    @item = item
  end

  def to_hash
    raise NotImplementedError
  end

  def to_json
    to_hash.to_json
  end

  private

  attr_reader :item
end

class BaseListPresenter
  def to_hash(items)
    items.map { |item| item_presenter.new(item) }
  end

  def to_json
    to_hash.to_json
  end

  def item_presenter
    raise NotImplementedError
  end
end


# BADGES PRESENTERS
class BadgePresenter < BasePresenter
  def to_hash
    {
      id: item.id,
      name: item.name
    }
  end
end

class BadgeListPresenter < BaseListPresenter
  def item_presenter
    BadgePresenter
  end
end