presenter.rb

require 'delegate'
# Public: This class initializes a presenter object.
# The presenter wraps a given object and a view object and will forward
# method calls to each. By default, any unknown method will be passed
# to the first object.
# Any methods that need to be sent to the view, may be done explicitly.
#
# Examples:
#
#   # Inside a controller you create a helper method to access this object
#
#   def presenter
#     @presenter ||= ProfilePresenter.new(@profile, view_context)
#   end
#   helper_method :presenter
#
#   # Inside the view, the "presenter" helper method may be accessed
#
#   <% presenter.with_military_branch do %>
#     <p><strong>Military Branch:</strong> <%= presenter.branch %></p>
#   <% end %>
#
class Presenter < SimpleDelegator

  # Private: Creates aliased method names for __getobj__ and __setobj__
  # which better reflect the wrapped object.
  #
  # Examples:
  #
  #   class ThingPresenter < Presenter; end
  #   presenter = ThingPresenter.new(thing, view)
  #
  #   presenter.respond_to?(:thing) #=> true
  #   presenter.respond_to?(:thing=) #=> true
  #
  def self.inherited(base)
    wrapped_object_name = base.name.split('::').last.sub('Presenter','').underscore
    base.send(:alias_method, wrapped_object_name, :__getobj__)
    base.send(:alias_method, "#{wrapped_object_name}=", :__setobj__)
  end

  # Private: This overrides the initialize method in SimpleDelegator and
  # calls super to wrap the given object. Then it sets the second argument
  # as the view.
  def initialize(object, view)
    super(object)
    @view = view
  end

  private

  attr_reader :view

  # Private: Enumerate a collection with the given block
  # wrapping each object with an instance of the given class
  #
  # Examples:
  #
  def wrapped_enum(wrapper_class, enumerable, &block)
    wrapper = wrapper_class.new(nil, view)
    enumerable.each do |slot|
      wrapper.__setobj__(slot)
      block.call(wrapper)
    end
  end

  delegate :current_page, :paginate, :link_to, to: :view
end