Last Updated: 2021-05-15
Say if an ActiveRecord method is only used in views. Then it (arguably) belongs in a presenter.
require 'redcarpet/render_strip' class ApplicationPresenter < SimpleDelegator def initialize(model) @model = model super(@model) end def short_description plaintext_renderer.render(@model.description) .truncate(80) .html_safe end private def plaintext_renderer Redcarpet::Markdown.new( Redcarpet::Render::StripDown ) end end class EpisodePresenter < ApplicationPresenter def published_on super.to_date.to_formatted_s(:long) end end
The way you'd use it is that the output of presenter would be assigned to an instance variable in the controllers.
class EpisodesController def show @episode = EpisodePresenter.new(episode) end end
The main issue I ran into was dealing with cases where the underlying object is nil / the empty array. For a while, I presented this "empty" object, but this was a bad idea since view logic that switches on truthiness breaks (e.g.
if @episode) since you cannot redefine truthiness of a whole object in Ruby. Therefore in future I would avoid presenting at all if the object is "empty".