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Powerful Interfaces @caike RailsConf 2012

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why developing Rails apps with fine-grained components is freaking awesome!

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Granularity

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Problems

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Not Fun! http://www.flickr.com/photos/lianneviau/499003712/sizes/l/in/photostream/

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Interface

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class Payment < ActiveRecord::Base def complete end def cancel end end

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end Client

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end Client Interface

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.save redirect_to(payment,success: 'You are now subscribed!') else render :index end end end

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.save redirect_to(payment,success: 'You are now subscribed!') else render :index end end end Coarse-Grained

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Callbacks Observers

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Three Laws of Interfaces

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do what its methods say it does. #1

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end

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Payment#save vs. Payment#place

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.place redirect_to(payment, success:'You are now subscribed!') else render :index end end end

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class Payment < ActiveRecord::Base protected :save ## # Add your comments here. # Really. Please do it :) ## def place end end

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do no harm. #2

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Registered Users

    <% User.recent.paginate(@page).each do |user| %>
  • <%= link_to(user.full_name, user) %>
    • <% end %>

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Registered Users

    <% User.recent.paginate(@page).each do |user| %>
  • <%= link_to(user.full_name, user) %>
    • <% end %>

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Registered Users

    <% @users.each do |user| %>
  • <%= link_to(user.full_name, user) %>
    • <% end %>

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notify client if something goes wrong. #3

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raise "Invalid HTTP request"

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raise "Invalid HTTP request"

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raise "Invalid HTTP request" vs. raise "PayX Authentication Error"

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raise "PayX Authentication Error"

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raise "PayX Authentication Error"

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do what its methods say it does. #1

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do no harm. #2

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notify client if something goes wrong. #3

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.save redirect_to(payment,success: 'You are now subscribed!') else render :index end end end

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.place redirect_to(payment,success: 'You are now subscribed!') else render :index end end end

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.place redirect_to(payment,success: 'You are now subscribed!') else render :index end end end doing too much

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Factory Method Pattern

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.place redirect_to(payment,success: 'You are now subscribed!') else render :index end end end

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class PaymentsController < ApplicationController def create payment = Payment.build_with(params[:payment]) if payment.place redirect_to(payment,success: 'You are now subscribed!') else render :index end end end

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class PaymentsController < ApplicationController def create payment = Payment.build_with(params[:payment]) if payment.place redirect_to(payment, success:'You are now subscribed!') else render :index end end end

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class PaymentsController < ApplicationController def create payment = Payment.build_with(params[:payment]) if payment.place redirect_to(payment, success:'You are now subscribed!') else render :index end end end

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class PlanSubscriber def self.build_for(user) end def subscribe(payment_info) end end

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class PaymentsController < ApplicationController def create payment = Payment.build_with(params[:payment]) if payment.place redirect_to(payment, success:'You are now subscribed!') else render :index end end end

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class PaymentsController < ApplicationController def create payment = Payment.build_with(params[:payment]) if payment.place redirect_to(payment, success:'You are now subscribed!') else render :index end end end

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class PaymentsController < ApplicationController def create plan_subscriber = PlanSubscriber.build_for(current_user) if plan_subscriber.subscribe(params[:payment]) payment = plan_subscriber.payment redirect_to(payment, success:'You are now subscribed!') else render :index end end end

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Design by Contract

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Pre-Conditions Post-Conditions Invariants

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Pre-Conditions

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User must have a valid email address. Product must be available.

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Pre-Conditions Post-Conditions

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User must have a new payment. Seat must be reserved.

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Pre-Conditions Post-Conditions Invariants

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User must be registered. Store location must be open.

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Pre-Conditions Post-Conditions Invariants

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Fat models Thin controllers

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Models != AR::Base

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class PaymentsController < ApplicationController def create payment = Payment.new(params[:payment]) if payment.save redirect_to(payment, success:'You are now subscribed!') else render :index end end end

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class PaymentsController < ApplicationController def create plan_subscriber = PlanSubscriber.build_for(current_user) if plan_subscriber.subscribe(params[:payment]) payment = plan_subscriber.payment redirect_to(payment, success:'You are now subscribed!') else render :index end end end

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Rails is not your application http://blog.firsthand.ca/2011/10/rails-is-not-your- application.html

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Extract your application into its own ruby gem.

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No content

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http://objectsonrails.com

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Rails Models Complexity Pyramid

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0 1 2 Rails Models Complexity Pyramid

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0 Rails out-of-the-box 1 2 Rails Models Complexity Pyramid

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0 Rails out-of-the-box 1 Protect AR::Base methods from controller 2 Rails Models Complexity Pyramid

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0 2 Rails out-of-the-box Hide AR::Base classes from controller 1 Protect AR::Base methods from controller Rails Models Complexity Pyramid

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Thank you. @caike