gistfile1.rb

class ActivityFeedDateRange < ActivityFeedDate
  def valid?
    start_date.present? && end_date.present?
  end

  def render
    day_range = "#{start_date.day}-#{end_date.day}"
    template.content_tag(:div, :class => "range-date-row") do
      template.render partial: 'shared/activity_feed_date_range', locals: { month: start_date.strftime('%b'), day_range: day_range, year: start_date.year }
    end
  end
end

class ActivityFeedSingleDate < ActivityFeedDate
  def valid?
    start_date.day == end_date.day
  end

  def render
    template.content_tag(:div, :class => "single-date-row") do
      template.render partial: 'shared/activity_feed_date', locals: { month: start_date.strftime('%b'), day: start_date.day, year: start_date.year }
    end
  end
end

class ActivityFeedDate
  include TemplateHelper
  include ValidRenderable

  attr_reader :start_date, :end_date

  def initialize start_date, end_date
    @start_date = start_date
    @end_date = end_date
  end
end

module ValidRenderable
  def valid?
    false
  end

  def render
  end
end

  def render_activity_feed_date
    start_date = parse_activity_date activityStartDate
    end_date = parse_activity_date activityEndDate

    valid_date_type = renderable_date_types.find do |type|
     type.new(start_date, end_date).valid?
    end

    valid_date_type.new(start_date, end_date).render
  end

  def renderable_date_types
    [
     ActivityFeedVariedDates,
     ActivityFeedSingleDate,
     ActivityFeedDateRange
    ]
  end