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Ruby from a Newbie
Ravi Shankar
Newbie Developer,
Amazon India Development Centre,
Chennai
Statutory Warning
You’re learning from a complete newbie who’s
determined to make a fool of himself
What are we looking at?
A little History behind Ruby
 Basics of Ruby
 Recommended Books
 Questions

History
One upon a time in South Japan
 Yukihiro “Matz” Matsumoto
 Developed in 95
 Current version is 1.8.5

But first
Ruby Interpreter
 Interactive Ruby Shell (irb)
 Ruby Interactive (ri)
 Hello, World!

Ruby who?
Completely OO
*Everything* is an object
Duck Typing and the likes
The duck test :
“When I see a bird that walks like a
duck, swims like a duck and quacks
like a duck, I call that bird a duck”
 Because it “ducks” the issue of typing
 Ruby is Dynamically and Strongly
typed
 Attributes and methods can be added
at run time

Data Structures
Numbers
Fixnum and Bignum – Transparently
Changed
Strings
Single Quote and Double Quote
 Comparable
 Slicable

Array
Hash
Ranges
Expressions and Operators
Every expression has a value
 Extra operator <=>
 Short Circuited Boolean operators
 and binds lower than &&
 or binds lower than ||
 For blocks and functions, the value of
the last statement it’s value
 === operator. We needn’t worry now

Conditional statements and
loops
Conditional, if and unless
 Looping while, until and for
 Inline expressions

Case expressions
Two forms
 Uses === operator for comparison

Functions
def foo
puts “What’s up doc?”
1
end
Closures
The way to iterate in Ruby
 Closure - Anonymous blocks of code
 Variables declared in the callee are
accessible to the called blocks
 Used in iterating
 Each Object declared iterators
accordingly

So, you want your own
iterators eh?
yield to be empowered!
 Remember :you can even add
iterators (for that matter anything!) to
existing classes

Regular Expressions
Built-in Support
 /reg-ex/ or %r{reg-ex}
 Used as ranges as triggers
 =~ and !~ operators
 $`, $& and $’

Classes in Rubyland
Constructor named initialize
 puts, gets are defined in Kernel
 Change Objects at runtime
 Operator overloading
 Garbage Collection
 Methods are public by default
 Attributes are private by default

What’s in a name?
local_variable
 ConstantName
 :symbol_name #Don’t worry about this
 @instance_variable
 @@class_variable
 $global
 ClassName ModuleName
 method_name

Accessors
Modules and Mixins
Modules are used as namespaces
 Modules can be used as mixins
 Mixins make multiple inheritance
possible

Exception Handling
begin
#So something
rescue ExceptionType
#hande it and call
#raise to rethrow is needed
ensure
#like finally in java
end
Things I haven’t covered
Only nil and false evaluate to false
 #{}
 File IO – straightforward
 retry, continue and redo in exceptions
 Backtick operator
 Global $ variables

Books that you can read
The pickaxe book – “Programming
Ruby, The pragmatic programmer’s
guide” will be all you need.
The first edition is freely available
 http://www.ruby-lang.org
 Why’s poignant guide to Ruby – an
amusing read

Questions?
Thank you!