Ruby on rails
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Ruby on rails
- 3. Part -2
- 4. Associations
- 5. Validations
- 6. Callbacks
- 7. Part -3
- 9. Migrations
- 10. Migration allows you to define changes to your database schema What is migration?
- 12. keep things synchronized
- 13. The model and scaffold generators will create migrations appropriate for adding a new model. Auto generated migrations
- 14. ruby script/generate model Product name:string description:text my_app/db/migrate/001_create_products.rb Creating a model
- 15. Migration generated class CreateProducts < ActiveRecord::Migration def self.up create_table : products do |t| t.string :name t.text :description t.timestamps end end def self.down drop_table :products end end
- 17. ruby script/generate migration AddPartNumberToProducts part_number:string my_app/db/migrate/002_AddPartNumberToProducts.rb Creating a Standalone Migration
- 18. Migration generated class AddPartNumberToProducts < ActiveRecord::Migration def self.up add_column :products, :part_number, :string end def self.down remove_column :products, :part_number end end
- 19. rake db:migrate also invokes the db:schema:dump task
- 22. def self.up create_table :people do |t| t.string :username, :null => false t.string :fname,lname t.text :notes t.timestamps end end def self.down drop_table :people end Creating a table
- 23. More transformations rename_column :people , :fname , :first_name rename_table old_name , new_name change_column table_name , column_name , type remove_column table_name , column_name add_index table_name , column_name drop_table table_name
- 24. More... change_table :products do |t| t. remove :description, :name t. string :part_number t. index :part_number t. rename :upccode, :upc_code end
- 25. Rollback rake db:rollback rake db:rollback STEP=3 rake db:migrate VERSION=20080906120000
- 26. ActiveRecord
- 27. ActiveRecord is a Module ActiveRecord (note no space) could be classed as a module, since it's an implementation of the Active Record design pattern. (* need to ask)
- 29. `id` int(11) NOT NULL auto_increment,
- 33. `created_at` datetime default NULL,
- 34. `updated_at` datetime default NULL,
- 36. ) ENGINE=InnoDB
- 37. One Object / instance Per Row
- 38. Table columns map to Object attributes
- 40. pluralized table names.
- 41. integer primary keys.
- 42. classname _id as foreign keys .
- 44. hides low level implementation
- 46. end
- 48. find method Examples: User. find (23) User.find(:first) User.find(:all, :offset => 10, :limit => 10) User.find(:first).articles
- 49. Find :select list = Person.find(:all, :select => "fname, lname" )
- 50. Find with :conditions Student.find(:all, :conditions => [‘first_name = ? and status = ?’ ,‘mohit’, 1] ) Why this ?
- 51. Find: Order By Person.find(:all, :order => ‘updated_at DESC’ ) SQL: SELECT * FROM people ORDER BY created_at;
- 52. Find: Group By Person.find(:all, :group => ‘designation’ ) SQL: SELECT * FROM people GROUP BY designation;
- 53. Find: Limit & Offset Person.find(:all, :limit => 10, :offset => 0 ) SQL: SELECT * FROM people LIMIT 0, 10
- 54. Dynamic find methods person = Person.find_ by_fname ("mohit") all_mohit = Person.find_ all_by_fname ("mohit") person = Person.find_ by_fname_and_lname ("mohit",”jain”)
- 55. Creating a new record user = User.new user.name = "David" user.occupation = "Code Artist“ user .save OR user =User. new (:name => "David", :occupation => "Code Artist") user .save OR user =User .create (:name => "David", :occupation => "Code Artist")
- 56. Update a record person = Person.find(123) person .update_attribute(:name, "Barney" ) OR person= Person.find(123) person .name = "mohit” person.save OR person=Person. update(12, :name => "jigar" , :email => "jigar@vinsol.com" ) update_all and update_attribute bypass the validations.
- 57. Delete a record Person. delete (123) OR person = Person.find_by_name("Mohit") person. destroy
- 58. Named and Anonymous Scopes
- 59. class Organization < ActiveRecord::Base has_many :people named_scope :active, :conditions => { :active => 'Yes' } end class Person < ActiveRecord::Base belongs_to :organization end Named scope
- 61. Named scope example 2 class Order < ActiveRecord::Base named_scope :last_n_days, lambda { |days| :condition => ['updated < ?' , days] } named_scope :checks, :conditions => {:pay_type => :check} end orders = Orders.last_n_days(7) orders = Orders.checks.last_n_days(7)
- 62. Anonymous scopes in_house = Orders.scoped(:conditions => 'email LIKE "%@pragprog.com"' ) in_house.checks.last_n_days(7)
- 63. Thank You.
- 64. Associations
- 66. has_one
- 67. has_many
- 69. has_one :through
- 70. has_and_belongs_to_many Types of associations
- 71. Whats the need ?
- 72. class Customer < ActiveRecord::Base end class Order < ActiveRecord::Base end OR class Customer < ActiveRecord::Base has_many :orders, :dependent => :destroy end class Order < ActiveRecord::Base belongs_to :customer end Comparison: without and with
- 75. One to One
- 77. One to Many
- 78. Its: has_many : orders and has_one : order
- 81. has_and_belongs_to_many Stories can belong to many categories. Categories can have many stories. Categories_Stories Table story_id | category_id has_many through: -- gives you a third model Person can subscribe to many magazines. Magazines can have many subscribers. Subscriptions Table person_id | magazine_id | subscription_type | subscription_length | subscription_date has_and_belongs_to_many vs has_many :through
- 82. Many to many
- 83. has_one :through
- 84. has_one:through* class Magazine < ActiveRecord::Base has_many :subscriptions end class Subscription < ActiveRecord::Base belongs_to :magazine belongs_to :user end class User < ActiveRecord::Base has_many :subscriptions has_one :magazine, :through => : subscriptions, :conditions => ['subscriptions.active = ?', true] end
- 86. Self refrentional Joins class Employee < ActiveRecord::Base has_many :subordinates , :class_name => "Employee" , : foreign_key => "manager_id" belongs_to :manager , :class_name => "Employee" end
- 87. When Things Get Saved class Order < ActiveRecord::Base has_one :invoice end class Invoice < ActiveRecord::Base belongs_to :order end continue...
- 88. When things get saved (continue) If you assign an object to a has_one/has_many association in an existing object, that associated object will be automatically saved. order = Order.find(some_id) an_invoice = Invoice.new(...) order.invoice = an_invoice # invoice gets saved continue...
- 89. When things get saved (continue) If instead you assign a new object to a belongs_to association, it will never be automatically saved. order = Order.new(...) an_invoice.order = orde r # Order will not be saved here an_invoice.save # both the invoice and the order get saved
- 90. Validations
- 91. validates_acceptance_of validates_confirmation_of validates_length_of validates_numericality_of validates_presence_of Validation Helpers
- 92. Example of validator helper class Person < ActiveRecord::Base validates_presence_of :name validates_uniqueness_of :name, :on => :create, :message => "is already used" end
- 93. When Does Validation Happen? new_record? instance method
- 94. Method triggers validations * create * create! * save * save! * update * update_attributes * update_attributes!
- 95. Method skips validations * update_all * update_attribute * update_counters * save(false)
- 96. valid? and invalid?
- 97. Validation Errors errors.add_to_base errors.add errors.clear errors.size
- 98. Displaying Validation Errors error_messages error_messages_for
- 99. Showing error message OR <%= error_messages_for :product %> <% form_for(@product) do |f| %> <%= f. error_messages %> #----- <% end %>
- 100. Callbacks
- 101. monitoring the process. The life cycle of a model object methods that get called at certain moments of an object’s lifecycle What are callbacks
- 102. Active Record defines 20 callbacks .
- 103. 18 call backs
- 104. after_initialize and after_find Rest two callbacks
- 105. 1.Instance method 2.Handlers Define callbacks:- in two ways
- 106. callback as instance method class class_name < ActiveRecord::Base # .. def before_save # .. end end
- 109. factor out code that doesn't really belong in models
- 110. class OrderObserver < ActiveRecord::Observer observe Order end
- 111. Instantiating Observers config.active_record.observers= :order_observer ( in environment.rb )
- 112. Thank you
- 113. Testing
- 114. 1. Unit 2. Functional 3. Integration Testing type
- 115. Unit testing? What and why
- 116. rake db:test:prepare copy the schema
- 117. rake test:units 1.copies the schema 2. runs all the tests in the test/unit
- 118. require 'test_helper' class ProductTest < ActiveSupport::TestCase # Replace this with your real tests. test " the truth " do assert true end end Test file?
- 119. Running a test ruby -I test test/unit /product_test.rb
- 120. Understanding with example of Product model
- 121. validates_presence_of :title , :description , :image_url validates_numericality_of :price validate :price_must_be_at_least_a_cent validates_uniqueness_of :title validates_format_of :image_url, :with => %r{(gif|jpg|png)$}i, :message => 'must be a URL for GIF, JPG ' + 'or PNG image.' protected def price_must_be_at_least_a_cent errors.add(:price, 'should be at least 0.01' ) if price.nil? || price < 0.01 end Product Model
- 122. test " invalid with empty attributes " do product = Product.new assert !product.valid? assert product.errors. invalid?(:title) assert product.errors. invalid?(:description) assert product.errors. invalid?(:price) assert product.errors. invalid?(:image_url) end Test 1
- 123. Run the test case ruby -I test test/unit/product_test.rb #Loaded suite test/unit/product_test #Started #.. #Finished in 0.092314 seconds. 2 tests, 6 assertions, 0 failures, 0 errors
- 124. Test 2 test "positive price" do product = Product.new(:title => "My Book Title" , :description => "yyy" , :image_url => "zzz.jpg" ) product.price = -1 assert !product.valid? assert_equal "should be at least 0.01" , product.errors.on(:price) product.price = 0 assert !product.valid? assert_equal "should be at least 0.01" , product.errors.on(:price) product.price = 1 assert product.valid? end
- 125. Fixtures sample data
- 126. ruby_book: title: Programming Ruby description: Dummy description price: 1234 image_url: ruby.png rails_book: title: Agile Web Development with Rails description: Dummy description price: 2345 image_url: rails.png YAML fixtures
- 127. Naming convention & usage fixtures :products Mention this in the ProductTest class :products => name of table and YML file
- 128. Fixture loading Loading involves three steps: * Remove any existing data * Load the fixture data * Dump the fixture data into a variable in case you want to access it directly
- 129. Test 3 (using fixture) test "unique title1" do product = Product.new(:title => products(:ruby_book).title , :description => "yyy" , :price => 1, :image_url => "fred.gif" ) assert !product.save
- 131. Thank you
- 132. WEB v2.0