Dinosaurs, Lasers, and the Decorator Pattern

Quick overview of the decorator pattern, and the implementation of that pattern in Rails in the form of the gem Draper. Also, dinosaurs and lasers.

1. Decorators in Rails by Miles Z. Sterrett
2. Get that HTML out of your model, you jerk by Miles Z. Sterrett
3. Dinosaurs, Lasers, and the Decorator Pattern by Miles Z. Sterrett
4. Wikipedia says: “In object-oriented programming, the decorator pattern is a design pattern that allows behaviour to be added to an existing object dynamically.”
8. Draper View Models for Rails https://github.com/jcasimir/draper
9. 1 require File.join(Rails.root, 'lib', 'slug') 2 class Job < ActiveRecord::Base 3 include IndyHackers::Slug 4 5 has_many :job_views 6 has_many :viewers, :through => :job_views 7 belongs_to :user 8 9 after_update :notify_if_published 10 11 scope :published, lambda { 12 where("jobs.published_at IS NOT NULL AND jobs.published_at <= ?", Time.zone.now) 13 } 14 15 def notify_if_published 16 if published_at_changed? && published_at.present? && published_at <= Time.now 17 SystemMailer.job_post_published(self.user, self).deliver 18 else 19 Rails.logger.info "OMG WTF BBQ" 20 end 21 end 22 end
10. 1 require File.join(Rails.root, 'lib', 'slug') 2 class Job < ActiveRecord::Base 3 include IndyHackers::Slug 4 5 has_many :job_views 6 has_many :viewers, :through => :job_views 7 belongs_to :user 8 9 after_update :notify_if_published 10 11 # ... 12 13 def pretty_job_date 14 published_at.strftime("%B %d %h:%m%P") 15 end 16 17 def viewers_total 18 "#{viewers.size} People Have Viewed This Post" 19 end 20 end
11. 1 .grid_10.prefix_1 2 %section.readable 3 %article.job#single-job 4 %h1= @job.title 5 %p= @job.pretty_published_at 6 %p= @job.viewers_total 7 .job-description 8 = MARKDOWN.render(@job.description).html_safe
12. 1 class JobDecorator < ApplicationDecorator 2 decorates :job 3 4 def published_at 5 # 'h' exposes Rails helpers w/i your decorator 6 # 'model' exposes the actual object you're decorating 7 h.l(model.published_at, :format => :murican_time) 8 end 9 10 def total_viewers 11 "#{model.viewers.size} People Have Viewed This Post" 12 end 13 14 def description_html 15 MARKDOWN.render(model.description).html_safe 16 end 17 end
13. 1 .grid_10.prefix_1 2 %section.readable 3 %article.job#single-job 4 %h1= @job.title 5 %p= @job.published_at 6 %p= @job.total_viewers 7 .job-description 8 = @job.description_html
14. 1 2 class JobsController < ApplicationController 3 def index 4 @jobs = JobDecorator.decorate(Job.published) 5 end 6 7 def show 8 @job = JobDecorator.find(params[:id]) 9 10 # or 11 # @job = Job.find(params[:id] 12 # @job = JobDecorator.new(@job) 13 end 14 end
15. Other Decorators • Active Presenter • Viewtastic • Delegate Presenter
16. La Fin Miles Z. Sterrett The Guy, Nearsited http://nearsited.net http://mileszs.com @mileszs