Rails - getting started

Rails - getting started

• 1.
  Rails Beginners Guide
• 2.
  Rails • Web applicationframework written in ruby • Based on Model View Controller architecture (MVC) • Uses core APIs and generators to – reduce the coding burden and – focus your efforts on value-adding development • Large community of developers – Provide support to each other – Write gems (libraries) to extend the framework (see rubygems.org) 6/16/2011 2
• 3.
  Why Rails • Productive – Programming in Ruby is simpler – Boiler plate already in place (e.g. binding objects between tiers) – Gems for re-usable features • Each to understand – Convention over configuration – Configuration-like programming e.g. ActiveRecord • Large community • Matur(e/ing) 6/16/2011 3
• 4.
  Setup Getting your environmentready
• 5.
  Install • MySQL 5.X •HeidiSQL (SQL Client) • Ruby 1.8.7 – http://www.ruby-lang.org/en/downloads/ – Note version • Rails – gem install rails –v=2.3.5 6/16/2011 Nokia Music 5
• 6.
  Project Setup • Createa database – mysql –u root -p – create database library; – GRANT ALL ON library.* TO ‘library’@’localhost’ IDENTIFIED BY ‘library ‘; – FLUSH PRIVILEGES; • Create a rails application – rails library 6/16/2011 Nokia Music 6
• 7.
  Project Setup • Configureyour application to communicate to the database – config/database.yml • development: • adapter: mysql • database: library • username: library • password: library • host: localhost 6/16/2011 Nokia Music 7
• 8.
  Concepts High-level Overview
• 9.
  Concepts • Rake • Routes • Migrations • Generators • Object relationships • Validates 6/16/2011 Nokia Music 9
• 10.
  Rake • Rake isruby’s build program (similar to make and ant) • Rake uses rakefiles to manage the build – Written in ruby – Default one created for rails which includes standard tasks • Rake tasks are namespaced • To see all the available rake tasks run rake –T or rake – tasks • Most commonly used rake tasks – rake db:migrate – migrate the database to the current version – rake db:rollback – move the database back a version – rake test – run all tests (unit tests and functional tests) 6/16/2011 10
• 11.
  Routes • The railsrouter matches incoming requests to controller actions • Routes are configured in config/routes.rb • Some generators add routes e.g. ruby script/generate scaffold cd name:string artist:string genre:string – Will add routes to add, delete, update, show, list posts • Routes can also be used to generate URLs for links, forms e.g. – link_to @cd.name, cd_path(@cd) – creates a link to the post show page • The routes API supports a multitude of operations, a common ones is: – map.resources :cds – creates CRUDL routes 6/16/2011 11
• 12.
  Migrations • Migrations allowyou to manage a database through versions • Each version is held in a separate timestamp prefixed file in db/migrate • Each migration knows how to update the database (self.up) and how to rollback (self.down) • Migrations are written in ruby and the migrations api supports a wide range of table and column alterations • You can also run normal SQL and ruby code • Every time a migration is run the <table> table is updated to include the timestamp • Migrations with rake db:migrate and rake db:rollback 6/16/2011 12
• 13.
  Generators • Command lineinterface to run code generators • Rails comes with a set of out of the box templates – You can customise these – You can add your own • Typically generate classes into your app directory e.g. – ruby script/generate model cd name:string artist:string genre:string – generates a model and associated files (tests, migrations) with the attributes specified – ruby script/generate scaffold cd name:string artist:string genre:string - creates not only the model but also a CRUDL controller and views – ruby script/generate migration add_record_label_to_cd – creates a single migration 6/16/2011 13
• 14.
  Object relationships • ActiveRecordis ruby implementation of the active record pattern (Martin Fowler 2003) • Set of meta-programming methods allow you to configure relationships in your model objects: – belongs_to :cd - for table holding pkey – has_many :tracks - notice the plural, for connected table – has_many :genres, :through => :cd_genres – to link through a relationship table • Then you can call methods on your model objects e.g. • @cd.tracks # array of tracks • @cd.genres # array of genres • @track.cd # cd model object 6/16/2011 14
• 15.
  Validations • Rails makesa set of validation methods available • Configure them in your model object • Rails validates on save and stores and saves it in <object>.errors • Some examples: – validates_presence_of :title, :artist – mandatory field checks – validates_uniqueness_of :title – each title can only be used once – validates_numericality_of :quantity – must be a number 6/16/2011 15
• 16.
  Console • Console letsyou run your application through the command line and test out pieces of code • To start a console session – ruby script/console • From there you can run ruby commands and will have access to all of your objects • The console saves a lot of time loading and reloading web pages to test functionality • Some useful commands – _ - provides access to the last result e.g. @cd = _ – puts @cd.to_yaml (or y @cd) – writes out an indented version of the object – reload! – reload the app – <tab> - autocompletes methods 6/16/2011 16
• 17.
  Simple Project A CDlibrary
• 18.
  Create your modeland scaffold • rails library • cd library • ruby script/generate scaffold cd name:string artist:string genre:string • rake db:migrate • ruby script/server • http://localhost:3000/cds 6/16/2011 18
• 19.
  Create relationships betweenmodels • ruby script/generate scaffold track name:string cd_id:integer • rake db:migrate • Create associations in the model classes – track.rb - belongs_to :cd – cd.rb - has_many :track • Allow tracks to select an album in track/edit.html.erb – <%= select( “track", “cd_id", Cd.all.map {|cd| [cd.name, cd.id]}, { :include_blank => "No part of an album" }, {:class => "fieldSelect"}) %> 6/16/2011 19
• 20.
  Next Where to gonext
• 21.
  Taking a stepbeyond the basics • Access other people’s shared code via gems and plugins – authlogic – controllers and UI to enable authentication – will_paginate – rich pagination for lists – cucumber – behaviour driven testing – faker – data generator – paperclip – file attachments • Caching – Rails.cache.read/write/delete and config for cache setup • Deployment with capistrano • Ajax via jQuery and format.js 6/16/2011 21
• 22.
  References Useful links
• 23.
  Further reading andvideos • Railscasts – http://www.railscasts.com – Video tutorials from Ryan Bates • Pivotal Labs - http://pivotallabs.com/talks – Wide range of talks including rails from leading tech company • has_many :through blog - http://blog.hasmanythrough.com/ – John Susser’s blog, senior rails developer at Pivotal Labs • Ruby Doc - http://www.ruby-doc.org/ – Ruby class documentation 6/16/2011 23