Basic presenters without gem

application_presenter.rb

class ApplicationPresenter
  def self.presents(name)
    define_method(name) do
      @object
    end
  end

  def initialize(object, template = nil)
    @object, @template = object, template
  end

  private

    def h
      @template
    end
end

connection_presenter.rb

class ConnectionPresenter < ApplicationPresenter
  presents :connection

  def connection_link
    if likely_private_messages_connection?
      ["#", { data: { toggle: "modal", target: "#expectations-modal" } }]
    else
      h.child_path(connection.child)
    end
  end

  private

  def likely_private_messages_connection?
    true
  end
end

presenters_helper.rb

module PresentersHelper
  def present(object, klass = nil)
    klass ||= "#{object.class}Presenter".constantize
    presenter = klass.new(object, self)

    if block_given?
      yield presenter
      nil
    else
      presenter
    end
  end
end

show.html.erb

<%= present connection do |connection_presenter| %>
  <%= connection_presenter.connection_link %>
<% end %>