Jim Fawcett CSE686

1
Jim FawcettCSE686 Internet ProgrammingSummer
2006
Ruby And Ruby on Rails
2
References

• Brown-Bag Seminar Presentation, Beyond Java
  Chapters 4 and 5, Jim Fawcett, Spring 2006
• Brown-Bag Seminar Presentation, Beyond Java
  Chapters 6 and 7, Taylan Yamliha, Spring 2006
• Beyond Java, Bruce Tate, OReilly, 2005
• Programming Ruby, Dave Thomas, PragmaticProgrammer
  , 2005
• Agile Web Development with Rails, Dave Thomas,
  David Hansson, PragmaticProgrammer, 2005

3
A Useful Definition for this Presentation

• Spin from WordReference.com
• A distinctive interpretation (especially as used
  by politicians to sway public opinion) the
  campaign put a favorable spin on the story.
• When spun, your job is to
• Listen, but be somewhat skeptical
• Make up your own mind

4
Some Spins

• Bruce Tate - Author of Beyond Java
• Java is nifty, but growing too complex for a lot
  of the jobs we need to do. Enter Ruby?
• Kanat Bolazar one of my Ph.D. candidate advisees
• Java is nifty, has lots of tools that let me do
  interesting research. I love it! Im skeptical
  of what the author says.
• Jim Fawcett - pragmatist
• Windows world is where most of the jobs are.
  There are lots of interesting, but complicated,
  technologies to use there. But windows
  development isnt the only game in town Its just
  the one I have most interest in.
• I think the author is smart, has lots of
  interesting things to say, and will give us a
  view into another world, if we let him.

5
(No Transcript)
6
Chapter 4 Glass Breaking

• Javas new job description
• Early use to develop quick applications
• Then moved server-side
• Web site applications
• Enterprise Systems
• Mapping objects into relational model
• Distributed transactions
• Messaging middleware
• Java is flexible, so its been able to accommodate
  these changes.

7
Typical Requirements

• Good fit to middleware development because of its
  existing packages
• Servlets and web programming is not as productive
  as PHP
• Java just isnt very good for the simplest and
  most typical applications.
• Better alternatives exist for XML processing.
  Javas strings are too verbose.
• Natural fit to large enterprise projects due to
  its libraries and large number of Java developers.

8
The Learning Curve

• Most Java-based web applications use Java Server
  Pages (JSP) technology, probably through Tomcat.
• There are more steps, now, in using Tomcat, which
  take longer to learn.
• But thats not all. Youll need to understand
• Ant build and deploy web applications
• Tapestry or Struts organize user interface code
• Hibernate object relational mapper
• Spring organize application resources and
  support testing

9
Resources

• See the End Notes for summaries of
• PHP Hypertext PreProcessor
• JSP Java Server Pages
• J2EE Java, Enterprise Edition
• EJB Enterprise Java Beans
• Apache Apache web server
• Tomcat Containers for Java Server Pages
• Struts Model-View-Controller application
  management
• Tapestry Simpler MVC application management
• Spring Frmwrk Framework for building containers
  of Java Server Pages
• BeeHive Builds object model on top of J2EE and
  Struts
• Hibernate Object-Relational mapper
• Ibatus Data mapper framework
• Maven Manage build, reporting, and documentation

10
Java for the Typcial Application

• For the basic problem, a web-based user interface
  for a relational database, you have to learn a
  lot more today than you did five years ago.
• The advanced frameworks will drive the Java
  language away from the base that made it popular

11
Agile Development

• Simplicity
• Use the simplest thing that will work
• Automated Unit Testing
• Junit framework is recommended
• Shortened Iterations
• Shorter schedules, better integration of customer
  feedback, and smaller iterations

12
Development Processes Java

• Javas community and tools provide excellent
  support for agile programming
• Java is not such a good language for agile
  development
• Not the simplest language
• Not friendly to very short iterations
• Because of the need for frameworks (implied)

13
Basic Java Limitations

• Frameworks make experienced Java developers more
  productive but make a steep learning curve for
  new developers.
• Compile-time type checking adds safety at the
  cost of additional time and syntax.
• Java is not able to express structured data
  leading to over-dependence on XML.
• Javas many compromises, like primitives
  (different than user types) make Java harder to
  learn and more complex to write.
• Java is nowhere near as dynamic as Smalltalk and
  Ruby.
• Javas long compile/deploy cycle is much longer
  than interpreted, dynamic alternatives.

14
Alternatives

• Are the Java community and large code base worth
  sacrificing the productivity of other
  alternatives?
• The waters are rising.
• A clean, dynamic language could gain footing in
  the gap between Visual Basic (6.0) and Enterprise
  Java.
• The lions share of Java development, even in the
  enterprise, is not full of distributed
  transaction and backbreaking loads.
• Developers want a way to baby-sit a big
  relational database with a web-based user
  interface.

15
Chapter 5 Rules of the Game

• Portability
• Must have a virtual machine for
• Security, portability, extensibility,
  interoperability
• Internet Focus
• The internet has two interfaces, for people and
  machines.
• The next language should build better interfaces
  more easily, using a component model.
• It should deal with XML productively and
  efficiently.
• Enterprise Integration
• The next language will should interoperate with
  the existing code base.
• Database Integration
• The language should access relational data in a
  natural, productive way.
• Transactions and Security
• Needs to integrate with existing enterprise
  security frameworks.

16
Generating Buzz

• Technically superior languages have failed
  because they didnt generate buzz.
• Walter Brights D is probably superior to C,
  but its generating little interest among the
  developer community.
• Without buzz there is no community
• Now is a good time for a new language
• Open source software makes it easier for smaller
  companies to become a force by virtue of numbers.
• Web services and other protocols make it easier
  to interoperate between languages.
• A JVM (or CLR) can support other languages.
• But generating buzz is more art than science, and
  perhaps more luck than art.

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Necessary Ingredients

• Economics
• Someone has to pay the check, and superior
  productivity makes that likely.
• Approachability
• New language needs to grab new users quickly to
  prosper.
• You should be able to get started quickly, and
  solve a problem that is important to you quickly.
• C was approachable because you could solve
  low-level problems with a high-level language.
• C was approachable because you could add C
  features to C, as you needed them.
• Java was approachable because the syntax was
  familiar and it had a clear path to internet
  applications.
• The killer App
• A language needs an active community to prosper.
• A killer application can quickly draw new users.
• Applets and servlets did that for Java.

18
Language Features

• Dynamic typing
• Static typing promotes safety through
  compile-time checks, at the cost of productivity.
• Dynamically typed languages are easier to explore
  and build prototypes.
• Code blocks
• Code blocks are anonymous functions that are used
  to quickly assemble callbacks, provide thread
  processing, and do repetitive operations on
  databases and collections.
• Theyre useful anywhere you need a once-only
  small function, and thats lots of places.
• They also reduce the remoteness factor.
• The function body is defined right where it is
  used.
• Continuations
• Saved stackframe hierarchies re-applied to go
  back to a prior state.
• Purported to be very useful for supporting
  backtracking in the stateless web model.
• Rapid feedback
• Reduce the time between making a change and
  seeing the result.
• The interpreted languages Smalltalk, Lisp, Perl,
  Ruby, and VB 6.0 all have rapid feedback and are
  very productive languages.

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More Language Features

• User Interface Focus
• User interface focus demands more than Java has
  to give.
• Dynamic Class Model
• A Java successor should be much more dynamic and
  reflexive.
• Javas reflection API is verbose, partly because
  of the distinction between primitives and user
  types.
• It has to deal differently with primitives,
  arrays, and classes.
• Tate gives two examples where a dozen lines of
  Java code are replaced with one or two lines of
  Ruby code.
• With Ruby you can also change classes, at
  runtime, on the fly. You can change a method on
  an object and leave the class untouched. Also,
  interceptions are childs play.
• Sound Foundations
• The next language should be object oriented and
  purer than Java.
• Here, the author means that primitives are first
  class objects.
• Consistency is important.
• Languages with consistent naming and behavior are
  far easier to learn.

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Potential Suitors

• Perl
• Productive scripting language
• Write only language with cryptic syntax
• Python
• A successful dynamic programming language, close
  to Ruby in syntax and power and supports the
  specified features.
• Syntax depends too much on white space.
• Has weak web development tools.
• Ruby
• Object oriented dynamic language, created in
  Japan, and just now becoming popular in US
• Beautiful syntax that stays out of your way.
• Highly dynamic
• Educated core of Ruby community works hard to
  produce clean, simple APIs.
• Has strong web frameworks, good support for XML
  and web services.
• Ruby has a couple of high profile frameworks,
  like Ruby on Rails.
• Ruby has good commercial backing in Japan, but
  not in US.
• JVM support is immature, though improving rapidly.

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More Suitors

• PHP
• Scripting language.
• Start with html and mark up with tags for
  scripted actions with databases and request and
  response objects.
• Easy to understand and learn.
• Good for controlling a database from a web page.
• Technically awful
• Couples user interface and database together.
• Method names are inconsistent.
• C and .Net Languages
• C is a Java clone with many of the same benefits
  and drawbacks.
• Microsoft languages are a closed ecosystem. They
  succeed or fail with the Microsoft platforms,
  rather than on their own merits.
• Smalltalk
• Never caught on commercially, despite attempts by
  IBM as late as 1995.
• Hughly productive, slightly awkward, and quirky
  to the extreme.
• Clean object model, incredible expressive power,
  and an intelligent design and community.
• Not seen as a credible alternative.
• It just wasnt ever approachable enough.

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A Random Quote from the Web

• I've been developing web apps for years, in both
  PHP and Java. You really notice how much stuff
  is repeated and unnecessary.  How many times do
  you enter the same variable or field name in the
  database, in the classes, in the HTML/view? It's
  a waste of time.I had developed some helper
  utilities that are basically a crude form of
  ActiveRecord (a Ruby on Rails construct).  I
  used to do a lot of Java development. J2EE
  _at_. Servlets, entity beans, etc. The amount
  of garbage you have to go through just to get
  something deployed made me angry.Seeing Rails
  was wonderful. It was all my "good ideas"
  implemented cleanly with none of the PHP hacks or
  Java verbosity.
• NoteThere are many quotables about Ruby on
  Rails that are favorable, and many that are not.

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Next UP

• Chapter 6 - Ruby in the Rough
• Chapter 7 Ruby on Rails

24
End Notes Chapters 4 and 5

• PHP, JSP, Java Beans, EJB, J2EE
• Apache, Tomcat, Spring Framework
• Struts, Tapestry
• BeeHive, Hibernate, IBatus
• Maven

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PHP - http//us3.php.net/manual/en/introduction.ph
p

• (recursive acronym for "PHP Hypertext
  Preprocessor") is a widely-used Open Source
  general-purpose scripting language that is
  especially suited for Web development and can be
  embedded into HTML.
• Simple answer, but what does that mean? An
  example
• Example 1-1. An introductory examplelthtmlgt  
  ltheadgt       lttitlegtExamplelt/titlegt  
  lt/headgt   ltbodygt       lt?php        echo "Hi,
  I'm a PHP script!"        ?gt  
  lt/bodygtlt/htmlgt

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JSP - http//www.webdevelopersjournal.com/articles
/jsp_build.html

• If you've ever used Microsoft's very popular
  Active Server Pages (ASP) then you'll have a good
  idea of what JSP is. It consists of HTML or XML
  markup into which special tags and code blocks
  are inserted. The code is executed on the server
  and the result is a dynamic page that is returned
  to the client browser. Although JSPs are simple
  to build they have at their disposal the full
  power of object-oriented Java and the Java Server
  API. JSPs make heavy use of Java Beans, which are
  classes that follow a standard pattern of a
  no-argument constructor (required in JSPs) and
  public GET and SET methods.

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Java Beans - http//en.wikipedia.org/wiki/Java_Bea
ns

• JavaBeans are software components written in the
  Java programming language.
• The JavaBeans specification by Sun Microsystems
  defines them as "reusable software components
  that can be manipulated visually in a builder
  tool".
• In spite of many similarities, JavaBeans should
  not be confused with Enterprise JavaBeans (EJB),
  a server-side component technology that is part
  of J2EE.
• In order to function as a JavaBean class, an
  object class must obey certain conventions about
  method naming, construction, and behavior. These
  conventions make it possible to have tools that
  can use, reuse, replace, and connect JavaBeans.
• The required conventions are
• The class should be serializable (able to
  persistently save and restore its state)
• It should have a no-argument constructor
• Its properties should be accessed using get and
  set methods that follow a standard naming
  convention
• It should contain any required event-handling
  methods
• Because these requirements are largely expressed
  as conventions rather than by implementing
  interfaces, some developers view Java Beans as
  Plain Old Java Objects that follow certain naming
  conventions. However, this view is misleading for
  Java Beans that support event handling, because
  the method conventions and associated support
  classes for event handling are fairly intricate,
  and require the use of specific base classes and
  interfaces.

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EJB - http//en.wikipedia.org/wiki/EJB

• The Enterprise JavaBeans specification is one of
  the several Java APIs in the Java 2 Platform,
  Enterprise Edition. EJB is a server-side
  component that encapsulates the business logic of
  an application.
• The specification details how an application
  server provides server-side objects known as
  Enterprise JavaBeans, or EJBs, with
• persistence
• transactions
• concurrency control
• events using Java Message Service
• naming and directory services
• security
• deployment of components in an application server
  
• remote communication using CORBA
• Additionally, the Enterprise JavaBean
  specification defines the roles played by the EJB
  container and the EJBs as well as how to deploy
  the EJBs in a container.

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J2EE - http//www.webopedia.com/TERM/J/J2EE.html

• Short for Java 2 Platform Enterprise Edition.
  J2EE is a platform-independent, Java-centric
  environment from Sun for developing, building and
  deploying Web-based enterprise applications
  online. The J2EE platform consists of a set of
  services, APIs, and protocols that provide the
  functionality for developing multitiered,
  Web-based applications. Some of the key features
  and services of J2EE
• At the client tier, J2EE supports pure HTML, as
  well as Java applets or applications. It relies
  on Java Server Pages and servlet code to create
  HTML or other formatted data for the client.
• Enterprise JavaBeans (EJBs) provide another layer
  where the platform's logic is stored. An EJB
  server provides functions such as threading,
  concurrency, security and memory management.
  These services are transparent to the author.
• Java Database Connectivity (JDBC), which is the
  Java equivalent to ODBC, is the standard
  interface for Java databases.
• The Java servlet API enhances consistency for
  developers without requiring a graphical user
  interface.

30
J2EE - http//en.wikipedia.org/wiki/J2EE

• Java Platform, Enterprise Edition or Java EE
  (formerly also J2EE) is a programming platform
  part of the Java platform for developing and
  running distributed multi-tier architecture
  applications, based largely on modular components
  running on an application server. The Java EE
  platform is defined by a specification. Java EE
  is also considered informally to be a language or
  standard because providers must agree to certain
  conformance requirements in order to declare
  their products as Java EE compliant albeit with
  no ISO or ECMA standard.
• Java EE includes several API specifications, such
  as JDBC, client-side applets, RPC, CORBA, and
  defines how to coordinate them. Java EE also
  features some specifications unique to Java EE
  for components. These include Enterprise Java
  Beans, servlets, portlets (following the JSR 168
  specification), JavaServer Pages and several web
  service technologies. This allows the developer
  to create an enterprise application that is
  portable between platforms and scalable, while
  integrating with legacy technologies.

31
Apache - http//httpd.apache.org/

• The Apache HTTP Server Project is an effort to
  develop and maintain an open-source HTTP server
  for modern operating systems including UNIX and
  Windows NT. The goal of this project is to
  provide a secure, efficient and extensible server
  that provides HTTP services in sync with the
  current HTTP standards.
• Apache has been the most popular web server on
  the Internet since April 1996. The November 2005
  Netcraft Web Server Survey found that more than
  70 of the web sites on the Internet are using
  Apache, thus making it more widely used than all
  other web servers combined.
• The Apache HTTP Server is a project of the Apache
  Software Foundation.

32
Tomcat - http//java.sun.com/products/jsp/tomcat/

• is a free, open-source implementation of Java
  Servlet and JavaServer Pages technologies
  developed under the Jakarta project at the Apache
  Software Foundation.
• Apache Tomcat is the servlet container that is
  used in the official Reference Implementation for
  the Java Servlet and JavaServer Pages
  technologies.

33
Spring Framework - http//www.springframework.org/
about

• The most complete lightweight container,
  providing centralized, automated configuration
  and wiring of your application objects.  The
  container is non-invasive, capable of assembling
  a complex system from a set of loosely-coupled
  components (POJOs) in a consistent and
  transparent fashion.  The container brings
  agility and leverage, and improves application
  testability and scalability by allowing software
  components to be first developed and tested in
  isolation, then scaled up for deployment in any
  environment (J2SE or J2EE).
• A common abstraction layer for transaction
  management, allowing for pluggable transaction
  managers, and making it easy to demarcate
  transactions without dealing with low-level
  issues. Generic strategies for JTA and a single
  JDBC DataSource are included. In contrast to
  plain JTA or EJB CMT, Spring's transaction
  support is not tied to J2EE environments.
• A JDBC abstraction layer that offers a meaningful
  exception hierarchy (no more pulling vendor codes
  out of SQLException), simplifies error handling,
  and greatly reduces the amount of code you'll
  need to write. You'll never need to write another
  finally block to use JDBC again. The
  JDBC-oriented exceptions comply to Spring's
  generic DAO exception hierarchy.
• Integration with Toplink, Hibernate, JDO, and
  iBATIS SQL Maps in terms of resource holders,
  DAO implementation support, and transaction
  strategies. First-class Hibernate support with
  lots of IoC convenience features, addressing many
  typical Hibernate integration issues. All of
  these comply to Spring's generic transaction and
  DAO exception hierarchies.
• AOP functionality, fully integrated into Spring
  configuration management. You can AOP-enable any
  object managed by Spring, adding aspects such as
  declarative transaction management. With Spring,
  you can have declarative transaction management
  without EJB... even without JTA, if you're using
  a single database in Tomcat or another web
  container without JTA support.
• A flexible MVC web application framework, built
  on core Spring functionality. This framework is
  highly configurable via strategy interfaces, and
  accommodates multiple view technologies like JSP,
  Velocity, Tiles, iText, and POI. Note that a
  Spring middle tier can easily be combined with a
  web tier based on any other web MVC framework,
  like Struts, WebWork, or Tapestry.

34
Struts - http//struts.apache.org/

• The goal of the Apache Struts project is to
  encourage application architectures based on the
  "Model 2" approach, a variation of the classic
  Model-View-Controller (MVC) design paradigm.
  Under Model 2, a servlet (or equivalent) manages
  business logic execution, and presentation logic
  resides mainly in server pages.
• The Apache Struts project encourages Model 2
  designs in two ways. First, by providing open
  source frameworks and toolkits that help
  developers build applications for the web.
  Second, by providing friendly and honest mailing
  lists where both newcomers and veterans discuss
  how to use Struts software in their own Model 2
  applications.

35
Tapestry - http//jakarta.apache.org/tapestry/inde
x.html

• Tapestry is an open-source framework for creating
  dynamic, robust, highly scalable web applications
  in Java. Tapestry complements and builds upon the
  standard Java Servlet API, and so it works in any
  servlet container or application server.
• Tapestry divides a web application into a set of
  pages, each constructed from components.
• Developing Tapestry applications involves
  creating HTML templates using plain HTML, and
  combining the templates with small amounts of
  Java code using (optional) XML descriptor files.
  
• In Tapestry, you create your application in terms
  of objects, and the methods and properties of
  those objects -- and specifically not in terms of
  URLs and query parameters. Tapestry brings true
  object oriented development to Java web
  applications.

36
BeeHive - http//beehive.apache.org/

• The Beehive goal is to make J2EE programming
  easier by building a simple object model on J2EE
  and Struts. Using the new JSR-175 annotations,
  Beehive reduces the coding necessary for J2EE.
  The initial Beehive project has three pieces.
• NetUI An annotation-driven web application
  programming framework that is built atop Struts.
  NetUI centralizes navigation logic, state,
  metadata, and exception handling in a single
  encapsulated and reusable Page Flow Controller
  class. In addition, NetUI provides a set of JSP
  tags for rendering HTML / XHTML and higher-level
  UI constructs such as data grids and trees and
  has first-class integration with JavaServer Faces
  and Struts.
• Controls A lightweight, metadata-driven
  component framework for building that reduces the
  complexity of being a client of enterprise
  resources. Controls provide a unified client
  abstraction that can be implemented to access a
  diverse set of enterprise resources using a
  single configuration model.
• Web Service Metadata (WSM) An implementation of
  JSR 181 which standardizes a simplified,
  annotation-driven model for building Java web
  services.
• In addition, Beehive includes a set of system
  controls that are abstractions for low-level J2EE
  resource APIs such as EJB, JMS, JDBC, and web
  services.

37
Hibernate - http//www.hibernate.org/

• Hibernate is a powerful, high performance
  object/relational persistence and query service.
  
• Hibernate lets you develop persistent classes
  following object-oriented idiom - including
  association, inheritance, polymorphism,
  composition, and collections.
• Hibernate allows you to express queries in its
  own portable SQL extension (HQL), as well as in
  native SQL, or with an object-oriented Criteria
  and Example API.

38
iBatis - http//ibatis.apache.org/

• The iBATIS Data Mapper framework makes it easier
  to use a database with Java and .NET
  applications. iBATIS couples objects with stored
  procedures or SQL statements using a XML
  descriptor.
• This framework maps classes to SQL statements
  using a very simple XML descriptor.

39
Maven - http//maven.apache.org/

• Maven is a software project management and
  comprehension tool. Based on the concept of a
  project object model (POM), Maven can manage a
  project's build, reporting and documentation from
  a central piece of information.

40
End of End Notes Chapters 4 and 5
41
Ruby

• Dynamic
• Fully object-oriented
• Interpreted

42
OO

• Everything is an object (ints, strings, etc.)
• irb(main)0020gt 7
• gt 7
• irb(main)0030gt 7.class
• Fixnum
• irb(main)0110gt 7.5.round
• gt 8
• irb(main)0120gt nil.class
• gt NilClass

43
Typing

• Dynamically typed
• irb(main)0130gt n1
• gt 1
• irb(main)0140gt n.class
• gt Fixnum
• irb(main)0150gt n"bbs"
• gt "bbs"
• irb(main)0160gt n.class
• gt String

44
Typing

• Strongly typed
• irb(main)0170gt n3
• TypeError cannot convert Fixnum into String
• from (irb)17in '
• from (irb)17

45
Conditionals

• irb(main)0200gt def silence?(b)
• irb(main)0211gt puts "aaaa" if b
• irb(main)0221gt end
• gt nil
• irb(main)0230gt silence? true
• aaaa
• gt nil
• irb(main)0250gt silence? false
• gt nil
• irb(main)0260gt silence? 0
• aaaa
• gt nil
• irb(main)0280gt silence? nil
• gt nil

46
Looping

• irb(main)0300gt puts line while line gets
• "aaa"
• "aaa"
• one
• one
• two
• two
• three
• three
• Z
• gt nil

47
Ranges

• irb(main)0310gt range 1..3
• gt 1..3
• irb(main)0320gt range.class
• gt Range
• irb(main)0330gt ('a'..'z')'h'
• gt true
• irb(main)0340gt ('a'..'z')'H'
• gt false
• irb(main)0350gt (1..10) 5
• gt true

48
Ranges

• irb(main)0360gt for c in 'g'.. 'j'
• irb(main)0371gt print c '-'
• irb(main)0381gt end
• g-h-i-j-gt "g".."j"
• irb(main)0390gt for c in 'g'.. 'j'
• irb(main)0401gt puts c
• irb(main)0411gt end
• g
• h
• i
• j
• gt "g".."j"

49
Regular Expressions

• irb(main)0420gt regex /better/
• gt /better/
• irb(main)0430gt regex.class
• gt Regexp
• irb(main)0440gt "Mine is bigger" regex
• gt nil
• irb(main)0450gt "Mine is better" regex
• gt 8

50
Containers - Hashes

• irb(main)0460gt numbers0gt"zero", 1gt"one",
  2gt"two", 3gt"three"
• gt 0gt"zero", 1gt"one", 2gt"two", 3gt"three"
• irb(main)0470gt 4.times i puts numbersi
• zero
• one
• two
• three
• gt 4

51
Containers - Arrays

• irb(main)0480gt stack 1,2,3
• gt 1, 2, 3
• irb(main)0490gt stack.push "cat"
• gt 1, 2, 3, "cat"
• irb(main)0500gt stack.pop
• gt "cat"
• irb(main)0510gt stack
• gt 1, 2, 3

52
Files

• A simple GREP
• File.open(ARGV0) do file
• rx Regexp.new(ARGV1)
• while linefile.gets
• puts line if line rx
• end
• end
• ruby grep.rb filename regex

53
Applying Some Structure

• Inside-out Refactoring
• Group common code in libraries
• Call them in your methods
• Outside in refactoring
• Your methods can
• take code-blocks as parameters
• call them
• even pass parameters to them

54
Outside-in Refactoring

• def threeTimes
•   yield
•   yield
•   yield
• end
• threeTimes  puts "Hello" 
• produces
• Hello
• Hello
• Hello

55
Classes

• calculator.rb
• class Calculator
• def initialize
• _at_total 0
• end
• def add(x)
• _at_total x
• end
• def subtract(x)
• _at_total - x
• end
• end

56
Classes

• irb(main)0010gt require calculator
• NameError undefined local variable or method
  calculator' for mainObject
• from (irb)1
• irb(main)0020gt require 'Calculator'
• gt true
• irb(main)0030gt c Calculator.new
• gt ltCalculator0x2bd2500 _at_total0gt
• irb(main)0040gt c.add 100
• gt 100
• irb(main)0050gt c.subtract 40
• gt 60

57
Classes

• irb(main)0060gt class Calculator
• irb(main)0071gt def reset
• irb(main)0082gt _at_total 0
• irb(main)0092gt end
• irb(main)0101gt end
• gt nil
• irb(main)0110gt c.reset
• gt 0

58
Classes

• irb(main)0120gt class IrsCalculator lt Calculator
• irb(main)0131gt def add(x)
• irb(main)0142gt x x/2 if xgt0
• irb(main)0152gt super
• irb(main)0162gt end
• irb(main)0171gt end
• gt nil
• irb(main)0180gt c IrsCalculator.new
• gt ltIrsCalculator0x2bba038 _at_total0gt
• irb(main)0190gt c.add 100
• gt 50

59
Classes

• irb(main)0200gt Class.superclass
• gt Module
• irb(main)0210gt Module.superclass
• gt Object
• irb(main)0220gt Object.superclass
• gt nil

60
Mixins

• Interfaces with implementation
• Can access the including classs methods
• Partly adds the benefit of multi-inheritance
• Implemented using Modules

61
Interceptors

• You can rename methods on-the-fly
• class Class
• alias_method orig_new, new
• def new(args)
• result orig_new(args)
• print Unattended laptop error!
• puts result
• return result
• end
• end

62
Interceptors

• irb(main)0010gt require "Class"
• gt true
• irb(main)0020gt a1,2,3
• ltRubyTokenTkIDENTIFIER0x2941d40gt
• ltRubyTokenTkASSIGN0x2941b48gt
• ltRubyTokenTkLBRACK0x2941950gt
• ltRubyTokenTkINTEGER0x29416c8gt
• ltRubyTokenTkCOMMA0x29414d0gt
• ltRubyTokenTkINTEGER0x2941278gt
• ltRubyTokenTkCOMMA0x29410b0gt
• ltRubyTokenTkINTEGER0x2940e70gt
• ltRubyTokenTkRBRACK0x2940c60gt
• ltRubyTokenTkNL0x2940438gt
• gt 1, 2, 3

63
Ruby On Rails

• What is it?
• Rails is a full-stack, open-source webframework
  in Ruby for writing real-worldapplications with
  joy and less code thanmost frameworks spend
  doing XML sit-upsDavid H. Hansson

64
Some Numbers

• The authors test case gives shows impressively
  superior numbers for Rails over
  Java/Spring/Hibernate solution in development
  time/code size as well as performance in most
  cases.

65
Architecture
66
Under the Hood

• Active RecordIts a wrapper around a db table,
  with domain logic built into the wrapper. You can
  also do inheritance and manage relationships.
• Action PackSplits the request into a controller
  part and a view part.

67
Showcases

• RubyBB by Russ Smith
• http//rubybb.readbim.com/
• 384 Lines of Code
• StoryCards Web app to support XP style dev. by
  Jim Weirich
• http//onestepback.org3030/
• 1,250 Lines of code 8 hours of development time
• Basecamp A commercial Rails web-app with over
  10,000 users.
• Web-based project management
• http//www.basecamphq.com/
• Launched after 4,000 Lines of Code.
• 2 man-months of months of programming by a single
  developer

68
End of Presentation