1. 229-511 Web Application Development Technology เทคโนโลยีสำหรับการพัฒนาโปรแกรม ประยุกต์เว็บ Suntorn Witosurapot Phone: 074 287369 or Email: wsuntorn@coe.psu.ac.th November 2009

2. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 2 Lecture 4 Database ’ s Table Relationships in Rails

3. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 3 Outline Review –Rails & MVC –Database & Data Modeling Rails and Databases –Active Record Basics –Mapping Cardinalities –Migrations Exercise

4. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 4 Review: Rails Web Framework for Ruby –Designed to make it easier to develop, deploy, and maintain web applications Rails has a benefit in productivity Comparing with J2EE: –J2EE currently has a benefit in scalability. If it ’ s a client facing system for millions of concurrent users – use J2EE. –If it ’ s an internal web application, definitely take a look at this technology as a possible way of shortcutting the long development time for a J2EE web app.

5. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 5 Review: Rails (cont.) Yes … they are fairly comparable ….

6. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 6 Review: Database Migration: A powerful and flexible tool for managing database changes Allows table, index, and data creation scripts to be run in multiple environments with a very simple syntax. –Need to revert back to a previous DB version to work on a bug? 1 command. –Then refresh it back to the current dev version? 1 command.

7. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 7 Example Migration

8. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 8 Review: MVC Model – Used for persistence & relationships View – Used for displaying the data Controller – The logic of the application

9. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 9 Rails and MVC Two Main components in Rails –Action Pack and Active Record Active Record –Create an idea of something in the database –Has predefined function which can be used –Don ’ t need to worry about underlying tech Action Pack –Controller and View are tightly coupled –Single Rails component –View code and Controller code are separate

10. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 10 Database development process Here, we will look at how to design a database that could be implemented in a relational database product (e.g., MySQL)

11. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 11 Data Modeling A data model is a collection of concepts for describing data. A schema is a description of a particular collection of data, using a given data model. The relational model of data is the most widely used model today. Main concept: relation, basically a table with rows and columns. Every relation has a schema, which describes the columns, or fields

12. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 12 Representing the Model Techniques to Represent Aspects of the Data Model

13. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 13 Representing Classes and Attributes Case study: >> Want to design a database table for each class. To design a database table for each class: Class Attributes will become the field or column names of the table When the data is added, each row (or record) in the table will represent an object

14. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 14 Representing Relationships Foreign key field the relationships between objects of different classes is established using the foreign keys.

15. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 15 Association between Tables Association represents relationship between database tables, whose relationship is constructed through foreign keys. –They express relationships like "Project has one Project Manager" or "Project belongs to a Portfolio". Cardinality relationship –One-to-one: A person has a single primary address –One-to-many: A school has many students –Many-to-many: A course has many students and each student take many courses.

16. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 16 Outline Review –Rails & MVC –Database & Data Modeling Rails and Databases –Active Record Basics –Mapping Cardinalities –Migrations Exercise

17. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 17 Active Record Object Relational Mapping (ORM) tool supplied with Rails Maps –Tables to classes –Rows to objects –Columns to object attributes determined at run time

18. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 18 Active Record Basics Create a subclass of ActiveRecord::Base class Employee < ActiveRecord::Base end Rails assumes that –the name of the table is the plural form of the class name –if the name contains multiple camel-case words, the table name has underscores between the words We don’t declare the attributes

19. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 19 Active Record in Rails Active Record is used for Model Ex: ruby script/generate model person –Will create app/models/person.rb class Person < ActiveRecord::Base end –Maps to ‘ people ’ table in database Columns automatically map to class variables of the same name

20. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 20 CRUD & Other Stuff Create Read Update Delete Other ActiveRecord Functions

21. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 21 Create Create row by creating object an_order = Order.new an_order.name = “Dave Thomas” an_order.address = “122 Main” an_order.phone = 2125551212 an_order.save Order.new do |o| o.name = “Dave Thomas” o.address = “122 Main” o.phone = 2125551212 o.save end an_order = Order.new( :name => “Dave Thomas”, :address => “122 Main”, :phone => 2125551212 ) an_order.save Note: We didn’t need to set a primary key. Rails assumes “id” is primary key and set auto-increment

22. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 22 Create Can also use create method Creates a new object and saves it Takes a hash or an array of hashes an_order = Order.create( :name => “Dave Thomas”, :address => “122 Main”, :phone => 2125551212 ) an_order = Order.create( [ { :name => “Dave Thomas”, :address => “122 Main”, :phone => 2125551212 }, { :name => “Another Name”, :address => “blah”, :phone => 1234567890 } ] )

23. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 23 Read We need to specify which rows we want –Rails will return objects containing the data from those rows in the database Use the find method with one or more primary keys –an_order = Order.find(27) –product_list = Order.find(params[ “ product_list ” ]) find() will throw a RecordNotFound exception if any of the requested primary keys cannot be found

24. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 24 Read find() also has other options –can pass :all or :first along with other parameters :conditions => “ name = ‘ Dave ’” –corresponds to WHERE clause :order => “ name ” –corresponds to ORDER BY clause :limit => pagesize –corresponds to LIMIT :offset => pagenum * pagesize –use in connection with :limit to step through query results an_order = Order.find(:first, :conditions => “name = ‘Dave Thomas’”) orders = Order.find(:all, :conditions => “name = ‘Dave’”, :order => “pay_type, shipped_at DESC”, :limit => 10)

25. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 25 Read Allowing for externally generated parameters –pname = params[:name] orders = Order.find(:all, :conditions => [“name = ?”, pname]) –orders = Order.find(:all, :conditions => [“name = :name”, {:name => pname}]) Can also write your own SQL –orders = Orders.find_by_sql(“select * from orders”) single parameter - SQL string –Nice for hard queries or performance

26. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 26 Update Simple –find the row or rows using find –update necessary fields –save Also works with an array for multiple update –orders = Order.find(:all, :conditions => “ name like ‘ Dave% ’” ) orders[0].name = “ Fred ” etc. May also use update() or update_all() –order = Order.update(123, :name => “ F ”, :address => “ blah ” ) finds, updates, saves, and returns object –result = Order.update_all( “ set clause ”, “ where clause ” ) returns number of rows updated order = Order.find(123) order.name = “Fred” order.save

27. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 27 Delete delete & delete_all –Order.delete(123) –Order.delete([1,2,3,4]) –Order.delete_all([“price > ?”, maxprice])

28. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 28 Other ActiveRecord Stuff Magic column names –id primary key –created_at, created_on, updated_at, updated_on automatically updated with timestamps –xxx_id foreign key Find by value of a particular column –Dynamically associates a find_by and find_all_by method with each column –order = Order.find_by_name( “ Dave Thomas ” ) –order = Order.find_by_address( “ 123 Main ” ) –orders = Order.find_all_by_email(params[ “ email ” ])

29. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 29 Outline Review –Rails & MVC –Database & Data Modeling Rails and Databases –Active Record Basics –Mapping Cardinalities –Migrations Exercise

30. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 30 Relationships between Tables Relationships are established using foreign keys Foreign key columns should be –named using the singular form of the table name with _id appended –example: a foreign key for the table products should be product_id This expresses relationship, but not the cardinality of the relationship

31. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 31 Specifying Relationships Relationships are specified by adding declarations to models –has_one, has_many, belongs_to, has_and_belongs_to_many Rule of thumb –Foreign key always has the belongs_to declaration

32. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 32 Note: the model for the table that contains the foreign key *always* has the belongs_to declaration One-to-one

33. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 33 One-to-many

34. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 34 Note: Many-to-many associations are symmetrical— both of the joined tables declare their association with each other using has_and_belongs_to_many. Many-to-many

35. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 35 Relationship methods Relationship declarations also introduce methods to the associated objects. –dynamically created –named using the table that it refers to Help navigate between the linked objects

36. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 36 Example class Product < ActiveRecord::Base has_many :line_items end class LineItem < ActiveRecord::Base belongs_to :product end item = LineItem.find(2) # item.product is the associated Product object puts "Current product is #{item.product.id}" puts item.product.title item.product = Product.new(:title => "Rails for Java Developers", :description => "...", :image_url => "http://....jpg", :price => 34.95, :available_at => Time.now) item.save! # save or raise exception puts "New product is #{item.product.id}" puts item.product.title Current product is 1 Programming Ruby New product is 2 Rails for Java Developers Note: ActiveRecord takes care of the details. It created a new product and linked the LineItem to it via the foreign key Result:

37. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 37 Q: Is it a belongs_to or has_one association? Recall: It depends on where you place the foreign key, which goes on the table for the class declaring the belongs_to relationship. class User < ActiveRecord::Base ??????? :account end class Account < ActiveRecord::Base ?????? :user end

38. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 38 Outline Review –Rails & MVC –Database & Data Modeling Rails and Databases –Active Record Basics –Mapping Cardinalities Exercise

39. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 39 Application Description: A basic musician database Each artist will be one individual with a name, age, and list of songs (not albums). Each song will have a title, duration and fit under one genre ( แนวเพลง ). This design is assumed that –an artist may consist of several individuals and may have multiple albums containing multiple songs, and –each song, artist and album can fit under a mesh of genres. Q1: How many entities are we keeping track of ? Q2: How many attributes are in each entity?

40. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 40 Identifying Entities & Attributes Artist: Has a name, age and songs. Song: Has a title, duration and fits under one artist and one genre. Genre: Each has a name, and houses many songs. We have the following entities and attributes:

41. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 41 Creating our App (themusic) Open Ruby console a shell window Create an application called themusic, by typing as Rails –d mysql themusic

42. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 42 Files & Folders created Many files and folders will be created for the application. Change to our app. directory

43. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 43 Create the Table structures using Scaffold 1.ruby script/generate scaffold artist name:string age:integer 2.ruby script/generate scaffold genre name:string 3.ruby script/generate scaffold song title:string duration:integer artist_id:integer genre_id:integer

44. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 44 Migration files

45. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 45 Create database & tables 1.rake db:create:all 2.rake db:migrate

46. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 46 Check whether the web app is ok? This is to make sure that everything is fine as it should be!

47. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 47 Adding Relationships Notice: Songs is plural

48. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 48 Interacting with Our App Via Console Rather than using web interface, we will interact with our app. via the ruby console ruby script/console

49. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 49 Let ’ s begin Creating an instance of the Artist model. Type the following and hit enter. jb = Artist.new(:name => 'Joe Bloggs', :age => 22) >> jb.age => 22 >> jb.id => nil >> jb.new_record? => true >> jb.name => "Joe Bloggs“ Simple Query:

50. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 50 Learning more >> jb.songs => [] Notice that the record gets an ID after it is saved: >> jb.save => true >> jb.id => 1 Q: Why? >> tune = Song.new(:title => 'Love Me Three Times', :duration => 456) => # nil, "title"=>"Love Me Three Times", "genre_id"=>nil, "duration"=>456}, @new_record=true> Save returns true on success. Trying to save our song as this point gives us errors: >> tune.save ActiveRecord::StatementInvalid: Mysql::Error: Column 'artist_id' cannot be null:... long trace omitted...

51. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 51 Learning more >> Genre.new(:name => 'Bluegrass').save => true >> Genre.new(:name => 'Goa Trance').save => true >> Genre.new(:name => 'Doo Wop').save => true >> Genre.new(:name => 'Blues Rock').save => true >> Genre.new(:name => 'Emo').save => true Let ’ s create some genres on the fly.

52. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 52 Learning more >> tune.genre = Genre.find_by_name('Blues Rock') Assign the tune a genre: >> tune.genre.name => "Blues Rock“ >> tune.genre_id => 4 See that it has been set (don ’ t worry if your ID differs) Use the Array object ’ s << operand to append to Joe Blogg's song array and then save it. >> jb.songs << tune >> tune.save => true

53. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 53 Exploration >> jb.songs[0].title => "Love Me Three Times" >> tune.artist.name => "Joe Bloggs" >> tune.artist_id => 1 >> bloggs = Artist.find_by_name('Joe Bloggs') Let ’ s fetch and create an instance of Joe Blogg ’ s record from the database Let ’ s explore this object further: >> bloggs.name => "Joe Bloggs" >> bloggs.songs[0].title => "Love Me Three Times" >> bloggs.songs[0].genre.name => "Blues Rock"

54. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 54 That ’ s the end You may try to add a few more artists and songs to the database For closing the console, type “ quit ”

55. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 55 Complete our exercise Using browser, let create an artist, e.g. Joe Bloggs

56. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 56 Change the default page Q: Which file does this screen generate? A: index.html

57. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 57 Task: Add a link to browse songs of the artist This is what it should be displayed as in our plan

58. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 58 Task: Add a link to browse songs of the artist (cont.) Q: How should we modify the original file of index.html.erb ?

59. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 59 Task: Add a link to browse songs of the artist (cont.) Answer: Step 1. Create code for link

60. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 60 Task: Add a link to browse songs of the artist (cont.) Add a method (also called action) called “browse” in the artist controller Answer: Step 2. Create an action in the controller

61. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 61 Task: Add a link to browse songs of the artist (cont.) Answer: Step 3. Create a view file for the action Generate a method (also called action) called “browse” in the artist controller

62. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 62 Result Screen

63. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 63 Backup

64. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 64 MySQL Workbench It is claimed a next-generation visual database design application that can be used to efficiently design, manage and document database schemata. This is extremely useful for drawing ER-diagram or Class Diagram in UML. Just the Community Edition is OK & available from http://dev.mysql.com/downloads/workbench/5.1.html http://dev.mysql.com/downloads/workbench/5.1.html The Windows version requires the.Net 2.0 framework which is integrated with Windows Vista. Windows XP SP2 users need to download the frameworkthe framework

65. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 65 Screenshots

66. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 66 Screenshots (cont.) Relationship Highlight

67. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 67 Screenshots (cont.) Mouse right-click at any table to edit table of attributes

68. 229-511 Web Application Development Technology Agile Programming, MVC Architecture & the practice with RoR 68 Screenshots (cont.) Export feature