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.

Transcript

1. Decorators
   in Rails
   by Miles Z. Sterrett
   

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2. Get that HTML
   out of your
   model, you jerk
   by Miles Z. Sterrett
   

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3. Dinosaurs,
   Lasers, and the
   Decorator
   Pattern
   by Miles Z. Sterrett
   

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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.”
   

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8. Draper
   View Models for Rails
   https://github.com/jcasimir/draper
   

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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
   

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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
    

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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
    

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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
    

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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
    

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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
    

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15. Other Decorators
    • Active Presenter
    • Viewtastic
    • Delegate Presenter
    

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16. La Fin
    Miles Z. Sterrett
    The Guy, Nearsited
    http://nearsited.net
    http://mileszs.com
    @mileszs
    

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