Presented By

Carl Zumbano and Sui Cheng

CS151 – Object Oriented ProgrammingMay 10, 2001

Ruby: An Introduction

• Created by Yukihiro Matsumoto in 1993 (named after his birthstone)

• Inspired (in part) by Eiffel and Ada

• Pure OO language (even the number 1 is an instance of a class)

• Highly portable, works on Linux, UNIX, DOS, Windows 95/98/NT/2K, Mac, etc.

Ruby: An Introduction

• Freely available and open-source.• More popular than Python in Japan,

probably b/c it handles mutibyte character sets so easily.

• Syntax is readable and easy to learn.• Being used for text processing, web apps,

general system administration, and AI and math research.

Ruby: the Language

• No multiple inheritance, but modules allow the importing of methods.

• Has garbage collection.

• Exception handling, like Java.

• Any class or instance can be extended anytime (even during runtime)

• Allows operator overloading.

Ruby: the Language

• Can be extended with Ruby or low-level C.

• No type declaration.

• Has iterators, methods which accept blocks for user-defined control structures (like loops)

• Emacs, TextPad, and Vim all have support available for Ruby.

Ruby: A Demonstration#Person Classclass Person

attr_accessor :name, :age def initialize(name, age)

@name = name @age = age.to_i

end def inspect

"#@name (#@age)" end

end

#Usage of the classp1 = Person.new('elmo', 4) p2 = Person.new('zoe', 7)

#Resultsp1 # -> elmo (4) p2 # -> zoe (7)

Ruby: A Demonstration

Now let’s take a look at Ruby in action…

Ruby Vs Java / C++

• Ruby– “Ruby”.length

– -5.0.abs

• C++ / Java– strlen(“Ruby”);

– s.length();

– abs(-5.0);

– number = Math.abs(number);

Advantages using Ruby against Java and C++

• Allow pass by code block • Support Regular Expression• Cleaner code

– No need to declare variables– Simple syntax (semi-colon is optional)– Every thing is an object, even a number. No

need to call separate function.– Simple object get/set methods declaration

Advantages (continue)

• Classes and modules are never closed. • Better Access Control

– Dynamic access control– Private methods never accessible directly by

another object

• Portable and extensible with third-party library

• Interactive environment

Disadvantages using Ruby against Java and C++

• No multiple inheritance– However, Ruby offers multiple-inheritance-like capabilities

• Ruby is a scripting language– However, Ruby can access to OS features, do same thing as

Perl and Python

• Different syntax and method definition style– Return statement is optional– Use of expression interpretation– Braces not needed in control statements (if, while)– Instance variable must preceded by “@”

Disadvantages (continue)

• Potential thread starvation in multi-threading– Use in-process thread [non-native]– However, it is lightweight and efficient

Closing

• Free download for Unix/Windows

• Applications includes:– X11 window manager, GUIs, managing server

machines and databases.

• Want to know more:– Visit http://www.ruby-lang.org

Ruby: References

• The Ruby Programming Language by Yukio Matsumoto; Addison Wesley Professional, 2000.

• Programming Ruby: A Pragmatic Programmer's Guide by David Thomas and Andrew Hunt; Addison-Wesley Pub Co, 2000.