Ruby on Rails

Ruby: The FoundationRails: The Framework

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Ruby on RailsAn Overview

J. Dew

Department of Computer Science and EngineeringUniversity of South Carolina

April 11, 2007

J. Dew Ruby on Rails

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Language BasicsCompletely Object OrientedMethods, Classes and Modules

Outline

1 Ruby: The FoundationLanguage BasicsCompletely Object OrientedMethods, Classes and Modules

2 Rails: The FrameworkModel-View-Controller ArchitectureDatabase-centric ProgrammingConvention over Configuration

3 Conclusion

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Ths Basics

Ruby is . . .A dynamic, open source programming language with a focuson simplicity and productivity. It has an elegant syntax that isnatural to read and easy to write.

http://ruby-lang.org/

Examplesputs "Hello World"

name = getsputs "Hello #{name}"

hash = {:id => 42}hash.has_key? :id

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Ths Basics

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Ths Basics

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Ths Basics

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Conditionals and Looping

Examples

3.downto(0) do |count|unless count == 0 then

print "#{count}.."else

puts "Blastoff!"end

end

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Conditionals and Looping

Examples

3.downto(0) do |count|unless count == 0 then

print "#{count}.."else

puts "Blastoff!"end

end

Produces 3..2..1..Blastoff!

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Everythings an Object

Examples42.methods.sort

returns

["%", "&", "*", "**", "+", "[email protected]", "-", "[email protected]","/", "", "[]", "^", "__id__","__send__", "abs", "between?", "ceil", "chr","class", "clone", "coerce", "display", "div","divmod", "downto", "dup", "eql?", "equal?",..."type", "untaint", "upto", "zero?", "|", "~"]

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Methods

Exampledef factorial(n)n == 1 ? 1 : n * factorial(n-1)

end

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Classes

Exampleclass Client

def Client.most_lucrative(clients)# class method

end

def paid_in_full!# instance method

end

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Modules

Example from Railsmodule ActiveRecord

class Base

def save# create or update a record

end

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Model-View-Controller ArchitectureDatabase-centric ProgrammingConvention over Configuration

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The Model

ConceptInteracts directly with the RDBMSMaintains the state of the applicationEnforces any rules or validations related to the dataEncapsulated by ActiveRecord in Rails

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The Model

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The Model

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The Model

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The View

ConceptResponsible for generating the UIWhere the HTML, JS, CSS, etc residesMostly printing variables and simple loopsActionView in Rails

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The View

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The View

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The View

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The Controller

ConceptCoordinates between the model(s) and the view(s)Responds to user input and routes accordinglyMost of the application logic goes hereActionController in the Rails framework

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The Controller

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The Controller

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The Controller

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Assumptions

Rails assumes thatyou have a RDBMS backendyou dont mind following certain naming conventionsyou want to be database agnosticyou think SQL embedded in your code is ugly

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Assumptions

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Assumptions

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Assumptions

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The PHP Way

PHP Code$dbh = mysql_connect("host","user","pwd");mysql_select_db(my_project);

$id = $_GET[id];$sql = "SELECT * FROM users WHERE id=$id";$result = mysql_query($sql);$row = mysql_fetch_assoc($result);

echo "Welcome, " . $row[first_name] . ".";

mysql_free_result($result);mysql_close($link);

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The Rails Way

Rails Database Configdevelopment:adapter: mysqlhost: hostusername: userpassword: pwddatabase: my_project

This would normally appear in config/database.yml.

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The Rails Way (continued)

Rails Controller [email protected] = User.find(@params[:id])

Rails View CodeWelcome,

In this case, the controller code would be found inapp/controllers/user_controller.rb and the modelcode would be found in app/models/user.rb.

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Object/Relational Mapping

What is Rails doing behind the scenes here?

ConceptMaps database tables to classesMaps rows to objectsMaps columns to attributes

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ORM Example

ExampleAssume you have a table with all of your employees stored in atable called employees.

Employee.find(:all) do |employee|if employee.last_name == "Dew"employee.salary = employee.salary * 2employee.save

endend

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Model Naming

ConceptDatabase names should be pluralClass names should be singular in mixed caseFilenames should be singular with underscores

ExampleIf you want a model for book orders, the database name shouldbe book_orders, the class should be named BookOrder,and stored in the file book_order.rb.

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Model Naming

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Model Naming

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Model Naming

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Why use Rails?

BenefitsEasy division of labor between programmers anddesignersLess time spent writing configuration filesProgrammers and/or designers new to a project knowwhere to find all assets in the projectDoing AJAX requests are just as easy as notVery nice and comprehensive community support anddocumentationAllows you to create complete web applications in days,not months

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Why use Rails?

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Why use Rails?

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Why use Rails?

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Why use Rails?

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Why use Rails?

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Why use Rails? (continued)

BenefitsRails (and Ruby) are open-source softwareSince Ruby is an interpreted language, it can be movedfrom platform to platform with very minimal changesRapid prototyping allows you to show your customer aworking demo instead of static mockups at the designmeetingsProven to be reliably scaleable

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Final Remarks

Apologies

I only began to scratch the surface of RubyMore information about Ruby can be found athttp://www.ruby-lang.org/

I only began to scratch the surface of RailsMore information about Rails can be found athttp://rubyonrails.org/

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Final Remarks

Apologies

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Final Remarks

Apologies

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Final Remarks

Apologies

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Questions?

Ruby: The FoundationLanguage BasicsCompletely Object OrientedMethods, Classes and ModulesRails: The FrameworkModel-View-Controller ArchitectureDatabase-centric ProgrammingConvention over ConfigurationConclusion