presenter.rb

# frozen_string_literal: true
# A generic presenter class
class Presenter < SimpleDelegator
  attr_reader :view

  class << self
    # Returns true if object has been wrapped in a Presenter
    def decorated?(object)
      object.is_a?(Presenter)
    end

    # Wrap object in presenter with access to a view context
    def present(object, view)
      return object if decorated?(object)
      new(object, view)
    end

    # Wrap each object in presenter with access to a view context
    def present_collection(collection, view)
      collection.map do |item|
        present(item, view)
      end
    end
  end

  def initialize(object, view)
    super(object)
    @view = view
  end

  def object
    undecorated(__getobj__)
  end

  private

  def decorated?(object)
    self.class.decorated?(object)
  end

  def present_collection(collection, presenter)
    presenter.present_collection(collection, view)
  end

  def undecorated(potentially_decorated_object)
    if decorated?(potentially_decorated_object)
      potentially_decorated_object.object
    else
      potentially_decorated_object
    end
  end
end

presenters_helper.rb

# frozen_string_literal: true

module PresentersHelper
  # Returns object wrapped in presenter. If object is a collection each member
  # of the collection is wrapped and the collection is returned.
  #
  # Example
  #
  #    <%- @foo = present(@foo, FooPresenter) -%>
  #
  def present(object, presenter)
    if object.is_a?(Enumerable)
      presenter.present_collection(object, self)
    else
      presenter.present(object, self)
    end
  end
end