WIXLIB

REST Architectural Principles The web has addressable resources.Each resource has a URI. The web has a uniform and constrained interface.HTTP, for example, has a small number ofmethods. Use these to manipulate resources. The web is representation oriented – providingdiverse formats. The web may be used to communicate statelessly– providing scalability Hypermedia is used as the engine of applicationstate.95-733 Internet Technologies5353

Back to Ruby: Methods# Methods may be defined outside classes# to form functions or within classes to# form methods. Methods must begin with lower case# letters.# If no parameters then parentheses are omitted.def testMethodreturn Time.nowenddef testMethod2Time.nowendputs testMethodputs testMethod2Output Tue Feb 10 22:12:44 -0500 2009Tue Feb 10 22:12:44 -0500 200995-733 Internet Technologies54

Methods Local Variablesdef looperi 0while i 5puts ii i 1endendlooperWhat’s the output?Output 0123495-733 Internet Technologies55

Scalers Are Pass By Value#scalers are pass by valuedef looper(n)i 0while i nputs ii i 1endendOutput 012looper(3)95-733 Internet Technologies56

Parenthesis Are Optional#scalers are pass by valuedef looper(n)i 0while i nputs ii i 1endendOutput 012looper 395-733 Internet Technologies57

Passing Code Blocks (1)def looper(n)i 0while i nyield ii i 1endendlooper (3) do x puts x endlooper (4) { x puts x }Output 012012395-733 Internet TechnologiesThink of the codeblock as a methodwith no name.Only one code blockmay be passed.Use procs orlambdas if youneed more.58

Passing Code Blocks (2)def looperi 0n 4while i nyield ii i 1endendValueValueValueValuelooper{ x puts "Value #{x}" }95-733 Internet Technologies0123Think of the codeblock as a methodwith no name.59

Passing Code Blocks (3)def interest(balance)yield balanceendWhat’s the output?interest is 150.0interest is 1120.0rate 0.15interestAmt interest(1000.0) { bal bal * rate }print "interest is #{interestAmt}"rate 0.12total interest(1000.0) { bal bal * (rate 1.0)}print "interest is #{total}"95-733 Internet Technologies60

Passing Code Blocks (4)Many Ruby methods take blocks.[1,2,3,4,5].each { x puts "Doubled #{x*2}"}DoubledDoubledDoubledDoubledDoubled95-733 Internet Technologies 2 4 6 8 1061

Passing Code Blocks (5)Many Ruby methods take blocks.Collect returns an array. What’s the output?t [1,2,3,4,5].collect { x x*2}puts tt [1,2,3,4,5].collect do x x 1 endputs t95-733 Internet Technologies2468102345662

Passing Code Blocks (6)XML Processing and XPATH predicates.# We want to read the schedule for this class.# For command line processing use ARGV[0] rather than hard coding the name.require "rexml/document” # Ruby Electric XML comes with standard distributionfile File.new( "schedule.xml" )doc es/Topic[. 'Ruby and Ruby On Rails']”) { element puts element } Topic Ruby and Ruby On Rails /Topic 95-733 Internet Technologies63

Or Remotelyrequire "rexml/document"require 'open-uri'remoteFile hedule.xml') { f f.read }doc //Slides/Topic[. 'Ruby and Ruby On Rails']") { e puts e }95-733 Internet Technologies64

Passing Code Blocks(7)# integers are objects with methods that take code blocks.4.times {puts "Yo!"}Output Yo!Yo!Yo!Yo!95-733 Internet Technologies65

Arrays and Hashes Are PassBy Referencedef coolsorter(n)n.sort!endn [5,4,3,2,1]coolsorter(n)puts nWhat’s the output?Output 1234595-733 Internet Technologies66

Classes# Classes and constants must begin with# an uppercase character.# Instance variable begin with an "@" sign.# The constructor is named initializeclass Studentdef initialize(n 5)@course Array.new(n)enddef getCourse(i)return @course[i]enddef setCourse(c,i)@course[i] cendendindividual Student.new(3)individual.setCourse("Chemistry", 0)puts individual.getCourse(0)Output Chemistry95-733 Internet Technologies67

Simple Inheritanceclass Mammaldef breatheputs "inhale and exhale"endendclass Cat Mammaldef speakputs "Meow"endendclass Dog Mammaldef speakputs "Woof"endendpeanut Dog.newsam Cat.newpeanut.speaksam.speaksam.breatheOutput WoofMeowinhale and exhaleRuby has no multiple inheritance.95-733 Internet Technologies68

Self makes a method a classmethod. @@ is a class variable.class Mammal@@total 0def initialize@@total @@total 1enddef breatheputs "inhale and exhale"enddef self.total createdreturn @@totalendendclass Cat Mammaldef speakputs "Meow"endendclass Dog Mammaldef speakputs "Woof"endendpeanut Dog.newsam ale and exhale2puts Mammal.total created95-733 Internet Technologies69

Public, Private and Protectedclass Mammaldef breathe # method is publicputs "inhale and exhale"endprotecteddef move# method available to inheritorsputs "wiggle wiggle"endprivatedef sleep# private methodputs "quiet please"endend95-733 Internet Technologiesclass Cat Mammaldef speakmoveputs "Meow"endendclass Dog Mammaldef speakmoveputs "Woof"endendpeanut Dog.newsam Cat.newpeanut.speaksam.speaksam.breathe70

Duck Typingclass Duckdef quackputs "Quaaaaaack!"enddef feathersputs "The duck has white and gray feathers."endendclass Persondef quackputs "The person imitates a duck."end95-733 Internet TechnologiesFrom Wikipedia71

Duck Typing (2)def feathersputs "The person takes a feather from the ground and shows it."endenddef in the forest duckduck.quackduck.feathersend# takes anything that quacks with feathersFrom Wikipedia95-733 Internet Technologies72

Duck Typing (3)def gamedonald Duck.newjohn Person.newin the forest donaldin the forest johnendgameFrom Wikipedia95-733 Internet Technologies73

Reflectionclass Dogdef barkputs "woof woof"enddef furputs "This dog likes you to pat her fur."endendscout Dog.newif(scout.respond to?("name"))puts "She responds to name"endif(scout.respond to?("bark"))puts "She responds to bark"puts scout.barkend95-733 Internet TechnologiesShe responds to barkwoof woof74

ModulesModules group together methods and constants.A module has no instances or subclasses.To call a module’s method, use the module name,followed by a dot, followed by the name of the method.To use a module’s constant, use the module name,followed by two colons and the name of the constant.Think “namespace”.95-733 Internet Technologies75

Modulesmodule StudentMAXCLASSSIZE 105class GradStudentdef workputs "think, present, present,."ruby onemodule.rbendthink, present, present,.def eatputs "pizza"enddef sleepInclude this module withputs "zzzzz"require. Similar to Java’sendendimport or C’s #include.endx 6mike Student::GradStudent.newmike.work if x Student::MAXCLASSSIZE95-733 Internet Technologies76

Mixinsmodule SomeCoolMethodsThe methods of amodule become membersof a class. Think “multipleinheritance” in Ruby.def fooputs "foo is running"enddef foo2puts "foo2 is running"endIf this were an externalmodule it would be ‘required’first. Then ‘included’.endclass CoolClassinclude SomeCoolMethodsendx CoolClass.newx.foo2‘require’ is like C’s include.‘include’ is used for mixins.95-733 Internet Technologies77

Ruby Supports ClosuresA closure is a first class function with free variablesthat are bound in the lexical environment.(From Wikipedia)Put another way: A closure is a method with twoproperties:1.It can be passed around and can be called at a latertime and2. It has access to variables that were in scope at thetime the method was created.From: Alan Skorkin’s “Closures – A simple explanation95-733 Internet Technologies78

Javascript has Closures Too!function foo(x) {return function() { alert("Hi " x); }}var t foo("Mike");var m foo("Sue");t();m();79

Javascript has Closures Too! html head script type "text/javascript” // define printMessage to point to a functionvar printMessage function (s) {alert("In printMessage() for " s)var f function () {alert(s ' was pressed.');}return f;}// call function pointed to be printMessage// with a parameter.// A pointer to a function is returned.// The inner function has a copy of s.buttonA printMessage('A')buttonB printMessage("B")buttonC printMessage("C”)80

Closures in Javascript /script title Closure example /title /head body !-- call the function pointed to by the variable -- button type "button" onClick "buttonA()" A Button Click Me! /button button type "button" onClick "buttonB()" B Button Click Me! /button button type "button" onClick "buttonC()" C Button Click Me! /button /body /html What’s the output?95-733 Internet Technologies81

Closures in JavascriptOn page load:In printMessage() for AIn printMessage() for BIn printMessage() for CThree buttons appearClick A “A was pressed”Click B “B was pressed”95-733 Internet Technologies82

A Closure in Rubydef foo (p)p.callend#call the procx 24#create a proc to passp Proc.new { puts x }foo(p)x 19foo(p)Quiz: What’s the output?95-733 Internet TechnologiesNote: It is easy topass two or moreprocs. Only onecode block may bepassed.Note: x is notwithin the scopeof foo.Note: a referenceto x is used. Not83a value.

A Closure in Rubydef foo (p)p.callend#call the procx 24#create a proc to passp Proc.new { puts x }2419foo(p)x 19foo(p)95-733 Internet Technologies84

Another Ruby Closureclass ACoolClassdef initialize(value1)@value1 value1enddef set(i)@value1 ienddef display(value2)lambda { puts "Value1: #{@value1}, Value2: #{value2}"}endenddef caller(some closure)some closure.callendobj1 ACoolClass.new(5)p obj1.display("some values")caller(p)p.call()obj1.set(3)95-733 Internet Technologiesp.callLambdas areprocs butwith arity checkingand different returnsemantics.Quiz: What’s theoutput?85

Another Ruby Closure (2)class ACoolClassdef initialize(value1)@value1 value1enddef set(i)@value1 ienddef display(value2)lambda { puts "Value1: #{@value1}, Value2: #{value2}"}endenddef caller(some closure)ruby closure.rbsome closure.callValue1: 5, Value2:endobj1 ACoolClass.new(5)Value1: 5, Value2:p obj1.display("some values")Value1: 3, Value2:caller(p)p.call()obj1.set(3)95-733 Internet Technologiesp.callsome valuessome valuessome values86

Pattern Matching#Pattern matching using regular expressionsline "http://www.andrew.cmu.edu"loc line /www/puts "www is at position #{loc}"Output www is at position 795-733 Internet Technologies87

Regular Expressions# This split is based on a space, period or comma followed# by zero or more whitespace.line2 "www.cmu.edu is where it's at."arr line2.split(/[ .,]\s*/)puts arr95-733 Internet TechnologiesOutput wwwcmueduiswhereit'sat88

Passing Hashesdef foo(a,hash)hash.each pair do key, val puts "#{key} - #{val}"endendfoo("Hello",{:cool "Value", :tooCool "anotherValue" })# Or, we may drop the parens foo "Hello" ,{:cool "Value", :tooCool "anotherValue" }95-733 Internet Technologies89

Ruby On Rails(1)“A framework is a system in which much of the more orless standard parts are furnished by the framework, sothat they do not need to be written by the applicationdeveloper.” Source: SebestaLike Tapestry and Struts, Rails is based on the Model ViewController architecture for applications.MVC developed at XeroxPARC by the Smalltalk group.95-733 Internet Technologies90

Ruby On Rails (2) Two fundamental principles:-- DRY (Don’t Repeat Yourself)-- Convention over configuration Rails is a product of a software development paradigmcalled agile development. Part of being agile is quick development of workingsoftware rather than the creation of elaboratedocumentation and then software.95-733 Internet Technologies91

Model View Controller The Model is the data and any enforced constraints onthe data. Rails uses Object Relationship Mapping.A class corresponds to a table. An object correspondsto a row. The View prepares and presents results to the user. The Controller performs required computations andcontrols the application.Source: Sebesta95-733 Internet Technologies92

Model View Controller§ Rails is a web-application and persistence framework.§ MVC splits the view into "dumb" templates that areprimarily responsible for inserting pre-built data inbetween HTML tags.§ The model contains the "smart" domain objects (suchas Account, Product, Person.§ The model holds all the business logic and knows how topersist itself to a database.§ The controller handles the incoming requests (such asSave New Account, Update Product, Show Person)by manipulating the model and directing data to the view.From the Rails README95-733 Internet Technologies93

Model View Controllerbrowser§controllerviewmodel95-733 Internet TechnologiesRDBMS94

Routerbrowser§Recognizes URL’s andchooses the controller andmethod to execute.controllerActionPackDynamic contentapproaches:view-ERB-XML Builder-RJS for Record95-733 Internet Technologies95

Rails Tools§ Rails provides command line tools.The following command creates many directoriesand subdirectories including models, views, andcontrollers: rails new greet cd greet rails generate controller sayAdd get ‘/say/hello’, to: ‘say#hello’ to the endof greet/config/routes.rbOr, add get '/say/hello', :to 'say#hello'Add an HTML file named hello.html.erb togreet/app/views/say rails server95-733 Internet Technologies96

Rails Directoriesgreetappcontrollerssay controller.rbviewssayclass SayController ApplicationControllerdef hellosay controllerhello method in controllerhello.html.erb95-733 Internet Technologies97

hello.html.erbviewssayhello.html.erb html !– all instance variables of thecontroller are visible here. - - body b Ruby says "Yo Mike". /b %a 32% Ruby is % a% degrees cool. /body /html 95-733 Internet Technologies98

Two Examples From Sebesta Hello world application Processing a Popcorn Form95-733 Internet Technologies99

Using NetbeansSee Tom Enebo’s NetBeans Ruby Project95-733 Internet Technologies100

Create an RoR Project95-733 Internet Technologies101

Select MySQL95-733 Internet Technologies102

Models Views and Controllers95-733 Internet Technologies103

Run And Visit Rails95-733 Internet Technologies104

Generate A Controller95-733 Internet Technologies105

Modify The Default Controller# The program say controller.rb is the specific controller# for the SebestaProject1 project.# Add the definition of the hello method.class SayController ApplicationControllerdef helloendend“hello” becomes part of the URL andtells the controller about the view.95-733 Internet Technologies106

Enter The View1.2.3.4.Select SebestaProject1/Views/SayRight ClickNew HTML fileFile name hello.html.erb html !– all instance variables of the controller are visible here. - - body b Ruby says "Yo Mike". /b %a 32% Ruby is % a% degrees cool. /body /html 95-733 Internet Technologies107

Run And Visit The ApplicationAs an exercise, include the helper call % link to "Cool", :action "hello" % in the html.95-733 Internet TechnologiesSo far, no model.108

Processing Forms95-733 Internet Technologies109

Result95-733 Internet Technologies110

routes.rbget '/home/the form', to: 'home#the form'post '/home/result', to: 'home#result'Quiz: How could these routes be written with :to ratherthan to: ?95-733 Internet Technologies111

The Home controller(1)class HomeController ApplicationControllerdef the formend95-733 Internet Technologies112

The Home controller(2)def result@name params[:name]@street params[:street]@city params[:city]@unpop params[:unpop].to i@unpop cost 3.0 * @unpop@caramel params[:caramel].to i@caramel cost @caramel * 3.5@unpop cost sprintf("%5.2f",@unpop cost)@caramel cost sprintf("%5.2f",@caramel cost)endend95-733 Internet Technologies113

The Form View(1) % form tag("/home/result", method: "post") do % table tr td % label tag(:name, "Buyer's Name:") % /td td % text field tag(:name) % /td /tr tr td % label tag(:street, "Street Address:") % /td td % text field tag(:street) % /td /tr 95-733 Internet Technologies114

The Form View(2) tr td % label tag(:city, "City, State, Zip:") % /td td % text field tag(:city) % /td /tr /table table border "border" tr th Product Name /th th Price /th th Quantity /th /tr 95-733 Internet Technologies115

The Form View(3)the form.html.erb tr td 3.00 /td td % label tag(:unpop, "Unpopped Corn 1 LB") % /td td % text field tag(:unpop) % /td /tr tr td 3.50 /td td % label tag(:caramel, "Caramel Corn 2 LB") % /td td % text field tag(:caramel) % /td /tr /table % submit tag("Submit Data") % % end % 95-733 Internet Technologies116

Results View(result.html.erb)(1) h4 Customer: /h4 % @name % br/ % @street % br/ % @city % p/ p/ 95-733 Internet Technologies117

Ø Rails, a web application development framework , was written in and uses Ruby Ø Ruby is general purpose but probably the most common use of Ruby is Rails Ø Rails was developed by David Heinemeier and released in 2004 Ø Basecamp (project management), GitHub (