Preview method for multiple types of panels

Question

Using Rubocop, pretty much any case statement is caught by the Cyclomatic Complexity cop, often the Assignment Branch Condition and method length cops as well. To get around this, I've been refactoring code like this:

def preview
  case object.panel_type
  when "image"
    asset_image_path(object.asset)
  when "profile_block"
    Profile.find(object.type_id).try(:full_name)
  when "slider"
    if object.options.present? && object.options["slides"].present?
      Slide.find(object.options["slides"][0]).headline
    else
      "Empty"
    end
  when "menu"
    Menu.find(object.type_id).try(:name)
  else
    clean_content.try(:truncate, (object.span * 4))
  end
end

Into this:

def preview
  if %w(image profile_block slider menu search_list).include?(object.panel_type)
    send("#{object.panel_type}_preview")
  else
    clean_content.try(:truncate, (object.span * 4))
  end
end

private

def image_preview
  asset_image_path(object.asset)
end

def profile_block_preview
  Profile.find(object.type_id).try(:full_name)
end

def slider_preview
  if object.options.present? && object.options["slides"].present?
    Slide.find(object.options["slides"][0]).headline
  else
    "Empty"
  end
end

def menu_preview
  Menu.find(object.type_id).try(:name)
end

def search_list_preview
  GridPanel::SEARCH_TYPES.invert[object.type_id]
end

In general, I think dynamic method names can be a bit problematic for maintenance. One of the problems with legacy Rails code is finding all the usage of dynamic methods in a project when you have to add or remove things. But in this case, I think the names have consistency and a limited scope, so it doesn't seem like it would be difficult to maintain or update later. Is there are more conventional way to do this?

Answer 1

I don't know your class but it looks like your object can have different subclasses depending on object.panel_type (maybe a single table inheritance?) and every subclass implements it's own preview method.

class Image < BaseClass
  def preview
      asset_image_path(object.asset)
  end
end

class Slider < BaseClass
  def preview
       if object.options.present? && object.options["slides"].present?
          Slide.find(object.options["slides"][0]).headline
       else
         "Empty"
       end
  end
end