SCRIPTING IN
RUBY
By Amber Bennett
“Ruby is simple in appearance, but is very complex inside, just like
our human body.” --Yukihiro Matsumoto
HISTORY
 Created by Yukihiro Matsumoto
 Initial release in 1995
 Matsumoto desired a scripting language with object-oriented support
Photo Credit: "Yukihiro Matsumoto EuRuKo 2011" by Mathias Meyer - http://www.flickr.com/photos/ipom/5862768190/. Licensed under Creative Commons Attribution-Share
Alike 2.0 via Wikimedia Commons - http://commons.wikimedia.org/wiki/File:Yukihiro_Matsumoto_EuRuKo_2011.jpg#mediaviewer/File:Yukihiro_Matsumoto_EuRuKo_2011.jpg
NAMES, BINDINGS, AND SCOPES
 Variable names can start with numbers, letters, and any combination of
the two
 They must start with a letter or an underscore
 Variable names are descriptive
 Case sensitivity:
 Class names must be capitalized
 Variable names are begun with lowercase letters
 Class variables
 Exist in the scope of a class
 Instance variables
 Unique to a given instance of a class
 Constants
 Do not change throughout execution of a program
 Can be reassigned, but interpreter will give a warning
DATA TYPES
 Dynamically typed
 Class variables start with @@
 Instance variables start with @
 Constants begin with a capital letter
 String type
 Number type
 Symbols
 Arrays and Hashes
 Abstract Data Types
 Provided through classes in Ruby
STRINGS: THE DIFFERENCE BETWEEN
SINGLE AND DOUBLE QUOTES
Double Quotes
 The code sample:
“The time is #{Time.now}”
 Prints out:
The time is 2014-05-23 07:26:12
+0000
Single Quotes
 The code sample:
‘The time is #{Time.now};
 Prints out:
The time is \#{Time.now}
SYMBOLS
1. # p039xysymbol.rb
2. know_ruby = :yes
3. if know_ruby == :yes
4.
puts 'You are a Rubyist'
5. else
6.
puts 'Start learning Ruby'
7. end
Source: http://rubylearning.com/satishtalim/ruby_symbols.html
ARRAYS AND HASHES
 Common among other languages
 0 indexed
 Arrays are defined by []
 Hashes are defined by curly braces in the format:
hash_name = { :key1 => “value1”, :key2 => “value2” }
EXPRESSIONS AND ASSIGNMENT
STATEMENTS
 Operators
 []
[]=
 *
/
 <=
Assignment
%
+
**
Arithmetic
=>
<
>
Comparison
 ..
…
 &
^
 ||
&&
Range
|
AND, XOR, regular OR (bitwise)
not
or
and
Logical operators
 Ternary operator:
 expression ?
value_if_true : value_if_false
STATEMENT-LEVEL CONTROL
STRUCTURES
 If-statements
 Then, else, end
1. if sum == 0 then
2.
 Case Expressions
3.
 Blocks
4.
if count == 0 then
result = 0
end
5. else
6.
7. end
result = 1
CASE EXPRESSIONS
OBJECT-ORIENTED SUPPORT
 Matsumoto created Ruby with object-oriented support in mind
 A lot of functionality when dealing with files
 Matsumoto “wanted a scripting language that was more powerful than
Perl, and more object-oriented than Python.”
Video!
CONCURRENCY AND EXCEPTION AND
EVENT HANDLING
 Logical concurrency
 Global Interpreter Lock (GIL)
 Exceptions can be caught using “rescue”
SOURCES
 Code samples taken from (unless otherwise specified):
 http://sandbox.mc.edu/~bennet/ruby/code/index.html