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Ruby On Rails


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A primer to Ruby on Rails introducing both Ruby and Rails.

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Ruby On Rails

  1. 1. Ruby on Rails Rapid, solid, flexible application development
  2. 2. I am ... Bálint Érdi (Budapest, Hungary) blog: email: My evolution :) java web developer python web developer (freelance) ruby web developer and consultant (with occasional non-web works)
  3. 3. Hungary
  4. 4. Legend Facts: (Wisdom :) ) Ruby is object oriented Code: 5.times { print "Hello Fluidtime!" }
  5. 5. Outline 1. Ruby basic concepts 2. Rails History & philosophy Basic modules Introducing each module Other features (a selection of them) Who uses Rails? 3. Demo app Questions are welcome anytime
  6. 6. Ruby: History created by Yukihiro Matsumoto ~1995 it is a blend of his favorite languages (Smalltalk, Lisp, Perl, ADA) open source [RUBY] now at 1.9
  7. 7. Ruby is object oriented But it really is Everything is an object Every object has a class Classes are objects, too 5.times { print "Hello, Fluidtime!" } 3 + 2 # => 5 3.+(2) # => 5 3.send(:+, 2) # => 5
  8. 8. Ruby is duck-typed (dynamically typed) behavior is more important than type ("if it walks like a duck and talks like a duck, it is a duck") no type declarations are needed a = 3 a + 2 # => 5 a + " jeff" # => TypeError a = "hello" a + 2 # => TypeError a + " jeff" # =>"hello jeff"
  9. 9. Ruby is functional programming like Functional programming methods are first-class citizens of the language lets you concentrate on what you want instead of how you want to do it (because "for" loops are ugly) Helps keep the code cleaner, more elegant and less error- prone. e.g Lisp [119, 43, 982, 266].select { |n| n % 7 == 0 } ["voodoo", "kayak", "light"].find { |w| w =~ /^(.).*1$/ } (1..4).map { |n| n**2 }
  10. 10. Ruby has strong metaprogramming features define methods at runtime, on the fly (define_method) evaluate code in the context of an instance or a class (instance_eval, class_eval) get in control when the object does not have a certain method (method_missing) ... or when a name is not found(const_missing)
  11. 11. Ruby has open classes, all of them Any class can be reopened, "core" classes, too you can define new methods, override new ones, etc. class definitions can thus span files class Numeric def plus(n) self.+(n) end end # => 5
  12. 12. Rails résumé Rails is a powerful yet simple web framework written in Ruby History Philosophy Introducing the main building blocks Other included features Extending Rails functionality Who uses Rails?
  13. 13. History created by David Heinemeier Hansson, ~2003 [ROR] extracted framework from a project called Basecamp open source, community driven, ~1400 contributors during its history now at 2.3, going for 3.0
  14. 14. Rails basic ideology Very opinionated: encourages "best practices" "Convention over configuration" to avoid bloatware and keep things simple in most cases Possibility to change default behavior in special cases Sugar and vinegar: easy to do what is encouraged, possible (but probably not simple) to do "unrecommended" things. Test Driven Development (TDD) is extremely important (writing tests first, so an automated test suit that can be easily -and quickly- run is needed) The framework has to stay small and lean but provide a mechanism for easy expansion.
  15. 15. Rails: Consequences of the ideology Why is all this important? enables you to be more productive by following the "guidelines" enables you to concentrate on the business logic without worrying about the technical details you will feel happy because it is so elegant and and feeling good! you will feel good because it is so efficient
  16. 16. Rails main building blocks Model - View - Controller (MVC) framework Model: ActiveRecord Controller: ActionController View: ActionView Clear separation of concerns Additional modules ActionSupport for supporting libs ActiveResource for REST compliance ActionMailer for sending emails
  17. 17. The model: ActiveRecord Database engine agnosticism Database migrations Associations between models Validations Callbacks
  18. 18. ActiveRecord: database agnosticism it is an ORM (Object Relational Mapping) you should not have to worry about what lies underneath you should not have to write SQL Adapters exist for sqlite, mysql, postgresql Post.find(:all, :conditions => [ "created_at > ?", 2.days.ago ])
  19. 19. ActiveRecord: Database migrations to make sure ... not just the code, but the database schema is tracked, too ... all developers work with the same schema ... you don't have to write raw SQL .. you are able to jump to any version, just like with a SCM ... deployment stays simple: you just run the migrations Examples of what a migration could do: creating a posts table adding a user_id to the posts table changing column type from boolean to string
  20. 20. ActiveRecord: Associations 1. class Blog < ActiveRecord::Base has_many :posts end class Post < ActiveRecord::Base belongs_to :blog has_many :comments end * using the control that Ruby gives for finding names (const_missing)
  21. 21. ActiveRecord: Associations 2. reaching associated object(s): blog.posts.find(:first, :conditions => ["updated_at > 1.week.ago]) creating associated object(s): post.comments.create(:user => me, :body => "That's a great post, congratulations!") * leveraging Ruby metaprogramming capabilities
  22. 22. ActiveRecord: Validations validation is business logic so it belongs to the model use the provided validators which cover most of the cases validates_presence_of :login validates_format_of :zip_code, :with => /^d{5}$/ roll your own for the special cases
  23. 23. ActiveRecord: Callbacks Entry points (hooks) that implement business logic at different during the lifecycle of the object lifecycle events: create, save, update, validate, destroy provided methods: before_save, after_create, ... good for setting default values, set calculated attributes, send out emails, etc.
  24. 24. ActionController: Résumé Basic buildup Filters Rendering from controller actions
  25. 25. ActionController: Basic buildup The controller should be thin and should only contain: ... actions (methods) that compose the API ... filter calls ... the actual filter implementations Actions new create edit destroy ...
  26. 26. ActionController: Filters Filters are ... methods that run before, after or around actions ... prevalently used for checking authorization to resources ... used to set variables for templates in a DRY way
  27. 27. ActionController: Rendering The controller sets the variables that the view template will use and does the actual rendering By default, the view with the name of the action is rendered But it can also render any action by name a text (mainly for debugging purposes) other representations of resources (e.g js, json, xml, etc.) nothing (just returning something to the caller)
  28. 28. ActionView: Résumé Basics Partials & content blocks
  29. 29. ActionView: Basics The view: ... is a representation ... should contain the least possible amount of business logic ... is rendered by the ERB template language which can be changed with plugins (check out haml! [HAML]) Lots of view helpers are provided for generating html some helpers (e.g form_for) are context-sensitive so views can be reused without cluttering them with conditions
  30. 30. ActionView: Partials & Content blocks Partials chunks of reusable code you can render from other views Content blocks separate definition of the building blocks of a page and actually generating them. make it possible to break the link between the order of html in the template and their order on the generated page are ideal for setting a subsection in the html title of a page injecting per-page javascripts
  31. 31. A selection of Rails' features Sending emails with ActionMailer Context-dependent configurations Routing RESTful applications Internationalization & Localization Generators Caching Extending core functionality Handling dependencies
  32. 32. Sending emails with ActionMailer mailers are models one email template (a view template) for each email type one method in the mailer model for each email type that sets the variables for rendering the email sending out an email is calling a method on the mailer there is convention for finding the template name from the method's name
  33. 33. Context dependent configurations (environments) Development: used for development with throwaway data Test: used for automated testing, records are created and destroyed by each test run. Production: used by the live application. Handle with care. Common configuration file + each env. has its own config which overwrites the values set in the common one. Additional environments can easily be set up Example: emails should be sent out in production, examined but not sent out when testing and it is up to you in development
  34. 34. Router generates user-friendly names you can use in your code (e. g dashboard_path and dashboard_url) makes your routes DRY. You don't have to put hardwired routes into your application makes dangling links nearly impossible routes incoming requests to the appropriate action it is a SEO tool map.dashboard '/', :controller => 'dashboard', :action => 'show' '/search/:term', :controller => "search", :action => "index", :term => /w*/
  35. 35. RESTful applications "HTTP is actually a general purpose protocol for applying verbs to nouns" [REST] encouraged as best practice declaring a resource generates the RESTful routes map.resources :users verb path generated path name GET /users/new new_user_path POST /users users_path GET /users/:id/edit edit_user_path(id) PUT /users/:id user_path(id) GET /users users_path DELETE /users/:id user_path(id)
  36. 36. Internationalization (I18n) & Localization Internationalization: Turns a one-language site into a international one Has translations for built-in messages (e.g for validation errors) for most languages Translations can easily be added in sep. "locale" files Localization: localizes displayed data to the actual language/country date, time, month names, day names, currency, etc.
  37. 37. Generators Generates files and content for common tasks Available from the command line Because laziness is a virtue in a programmer :) Models, controllers, resources, migrations, Plugins can easily add their generators
  38. 38. Caching Granular: page caching Static pages that do not need Rails to enter the picture (e.g about us, terms & conditions) action caching Pages that rarely change but that need certain filters to run (e.g pages that can only viewed once logged in) fragment caching only cache certain parts of a page (e.g sidebar)
  39. 39. Consistent core, dead simple extension User authentication, pagination, attaching files, etc. to models are not part of Rails Possible extensions: plugins are bundled with the application gems can be bundled with the application (which is good practice to do) or installed system-wide
  40. 40. Handling dependencies vendor directory for dependencies: vendor/gems vendor/plugins vendor/rails and automated tasks to manage them Examples: $ rake rails:freeze:edge $ rake gems:unpack:dependencies
  41. 41. Who uses Rails? - social coding - issue tracker app - webshop generation and hosting ... from small-scaled applications to high-traffic ones for really simple stuff it could be an overkill (in these cases use Sinatra, another ruby framework :) [SIN])
  42. 42. Time for a demo app! http://github. com/balinterdi/par_avion/tree/maste r
  43. 43. Questions? Bálint Érdi blog: email: twitter:
  44. 44. References [HAML] [RUBY] [ROR] [REST] [SIN]