Ruby Language - A quick tour

The Ruby Programming
Language
- Quick Tour

Wang_Wei@opi-corp.com

TOC

1.Overview
2.Installation & IDE
3.Structure & Execution
4.Data types & Objects
5.Expression & Operators
6.Statement & Control Structure
7.Method,Block,Proc,Lambda
8.Class & Module
9.Reflection & Metaprogramming
10.Gems & Rake
11.Books & Links & Persons

Overview - Birthstone

January - Garnet February - Amethyst

March - Aquamarine April- Diamond

May - Emerald June - Pearl

July - Ruby August - Peridot

September - Sapphire October- Tourmaline

November - Yellow Topaz December - Blue Topaz

Overview

•Pure OO,Everything is Object,Yes!Everything
5.times{|i|puts i}

•Highly Dynamic
class HelloWorld;end
HelloWorld.send(:define_method,:say){puts "HelloWorld!"}

•Excute while parsing
class Klass
puts "Hello"
end

•Cross Platform
Windows,Linux,Unix,Mac,...

•Open Source
http://www.ruby-lang.org/en/downloads/

To C++ Programmer

•No variable declaration
•ONLY false & nil are falsy
•'constructor' is called 'initialize'
•All methods are always 'virtual'
•First letter is important: $,@,@@,Klass,i
•Member variables are private
•Use 'self' instead of 'this'
•?,! ARGV.size.zero? obj.nil? str.strip!
•Single Inheritance, Mixin to help
•Parentheses & semicolons are usually optional
•Classes are not sealed!can be reopen
•No Generic/Template
•Iteration are easy
•There's only two container: Array,Hash
•Almost everything is an expression

Installation & Implementations

•Windows
One-Click Installer, Zip

•Ubuntu
sudo apt-get install ruby1.8/ruby1.9
sudo apt-get install irb1.8/irb1.9

•Mac
port install ruby

•Implementations
c ruby, JRuby, IronRuby

•Version
ruby1.8 ruby1.9

"IDE"

•Windows/Linux
Eclipse+RDT, *RubyInSteel*,
NetBeans,IDEA,RadRails,3rdRails
Notepad++/Ultraedit/Editplus+irb

•Mac
Textmate

Structure & Execution

#!/usr/bin/ruby shebang comment
# -*- coding: utf-8 -*- coding comment
require 'erb' loading library

class Klass define class
include Enumerable include module
def k
require 'socket' loading library
...
end
end
if $0 == __FILE__
o=Klass.new.k create object
DATA.read
end
__END__
embeded string embeded string resource

Data types - Number

dec = 123 dec.class==Fixnum
million = 1_000_000
hex = 0xFF
binary = 0b0010
octal = 0377
float = 1_000.0 float.class==Float
2**1024 =
179769313486231590772930519078902473361797697894230657273430081157732675805500963132708477
322407536021120113879871393357658789768814416622492847430639474124377767893424865485276302
219601246094119453082952085005768838150682342462881473913110540827237163350510684586298239
947245938479716304835356329624224137216
(2**1024).class==Bignum

Conversion:
other_type.to_i
other_type.to_f

Data types - Text

variable_name = %PREFIX SYM content SYM
SYM = [~`!@#$%^&*_-+=|:;"',.?/] + [] {} ()
name = 'Jack' No Escape!
name = %q[Jack]
name = %q{Jack} PREFIX = [%q,%Q,%x,%r,%s]
name = %q!Jack! Backtick command Execute
name = %q|Jack| %x[notepad] `notepad`
name = %q+Jack+
name = %q-Jack- Regular expression
name = %q=Jack= %r[hello] /hello/
name = %q,Jack,
name = %q.Jack. Array literal
name = %q/Jack/ %w[hello world] => ['hello','world']
name = %qJack %W[hello world] => ["hello","world"]
...
all symbol on Symbol literal
keyboard! %s[symbol]

Data types - Text

a = "Hello" + "World" => "HelloWorld"
a.sub("World","There") => "HelloThere" sub!
a.gsub(/o/,"*") => "Hell*W*rld" gsub!
a.chomp("d") => "HelloWorl"
a.center(15,"=") => "===HelloWorld==="
a.ljust(16) => "HelloWorld "
a.rjust(16) => " HelloWorld"
a.capitalize => "Helloworld"
a.upcase => "HELLOWORLD"
a.downcase => "helloworld"
a.reverse => "dlroWolleH"
a.swapcase => "hELLOwORLD"
a.length => 10
a.size => 10
a.count('o') => 2
a.include?('o') => true
"BBBBBaaaaaadddd".squeeze => "Bad"

Data types - Text

a = "Hello World!"
a[index] a[0] => "H"
a[from,count] a[0,5] => "Hello"
a[range] a[0...-1] => "Hello World"
a[-6..-1] => "World!"
a[regex] a[/W.*?!/] => "World!"

a.split(/[ !]/) => ["Hello", "World"]
a.split.join(",").concat("~") => "Hello,World!~"
a.sub(" ",",") << "~" => "Hello,World!~"

Conversion:
everything.to_s

Data types - Here Document

str = <<-STR.gsub("world","there")
hello world
hello world hello world hello world
hello world
hello world
hello world
STR

cpp_tepmlate = <<-CPPTPL
class <%=name%> : public <%=basename>
{
public:
<% methods.join("n") %>
};
CPPTPL
result = ERB.new(cpp_template).result(binding)

Data types - Array

As Vector:
a = [1,"h",3.14]
n = %w[1 2 3] => ['1','2','3']
e = %W[s t r n] => ["s","t","r","n"]
empty = Array.new => []
nils = Array.new(3) => [nil,nil,nil]
[0]*3 => [0,0,0]
copy = Array.new(nils) => [nil,nil,nil]
Array.new(3){|i|i} => [0,1,2]

As Set:
[1,2]+[3,4] => [1,2,3,4]
[1,2,3,4] - [1,2] => [3,4]
[1,2] | [2,3] => [1,2,3]
[1,2] & [2,3] => [2]

As Stack:
[1,3].push(3,4) => [1,2,3,4]
[1,2,3].pop => [1,2]

As Queue:
[1,2,3,4].shift => [2,3,4]
[3,4,5].unshift(2) => [2,3,4,5]

Data types - Array

As List:
a = [1,2]
a.concat(3) => [1,2,3]
a << 1 => [1,2,3,1]
a.insert(a.index(2),'a') => [1,'a',2,3,1]
a.delete("a") => [1,2,3,1]
a.delete(1) => [2,3]
[1,2,3,4].reject{|e|e%2==0} => [1,3]

As Sequence:
a = ('a'..'c').to_a => ['a','b','c']
a[0,1] => ['a']
a[0..2] => ['a',b','c']
a[0..-2] => ['a','b']

Iteration:
a = [1,2,3]
a.each{|e| print(e)} => 123
a.each_with_index{|e,i| print("#{i}:#{e},")} => 0:1,1:2,2:3,
a.inject(0){|s,e|s+=e} => 6

for i in a
print(i)
end => 123

Data types - Array

Conversion:
other_type.to_a
(1..10).to_a => [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
('a'..'c').to_a => ['a','b','c']

('ab'..'bf').to_a => ["ab", "ac", "ad", "ae", "af", "ag",
"ah", "ai", "aj", "ak", "al", "am", "an", "ao", "ap", "aq",
"ar", "as", "at", "au", "av", "aw", "ax", "ay", "az", "ba",
"bb", "bc", "bd", "be", "bf"]

{:a=>1,:b=>2}.to_a => [[:b, 2], [:a, 1]]

Data types - Hash

As HashTable:
j = {"name"=>"jack",:age=>25}
j["gender"] = "male"

Iteration:
j.each{|k,v| ... }

for k,v in j
...
end

Conversion:
j.to_a => [["name", "jack"], [:age, 25]]
j.to_s => "namejackage25"

Data types - Range

1..10 => 1..10 (iterable, to_a)
1.0..1.5 => 1.0..1.5 (un-iterable,no to_a)
cold_war => 1945..1989
letter = 'a'..'z' => 'a'..'z' (to_a)

Iteration:
n = 3
(1..n).each{|i|print(i)} => 123
for i in (1..n)...

Membership test:
(1..100).member?(50) => true
(1..100).include?(50) => true
(1..100).cover?(2..50) => true (1.9)

Data types - Symbols

:symbol => :symbol
:name => :name
:'with quote' => :'with quote'
:"hello #{:name}" => :"hello name"

Conversion:
:name.to_s => "name"
"name".to_sym => :name
"name".intern => :name
"name".id2name => :name

Symbol Table:

symbols are entris in symbol table of interpreter
symbols have an index in symbol table while string have not

Data types - True,False,Nil

Ruby has NO Boolean type!!!
true.class => TrueClass
false.class => FalseClass
nil.class => NilClass

true.nil? => false
false.nil? => false
nil.nil? => true

Only false&nil are falsy,everything else are truthy:
puts "hi" if nil => nil
puts "hi" if false => nil

puts "hi" if true => "hi"
puts "hi" if 0 => "hi"
puts "hi" if 0.0 => "hi"
puts "hi" if "" => "hi"
puts "hi" if [] => "hi"
puts "hi" if {} => "hi"

Expression & Operators

Class Variable @@[_a-z][_a-zA-Z0-9]*
Instance Variable @[_a-z][_a-zA-Z0-9]*
Global Variable $[_a-z][_a-zA-Z0-9]*
Local Variable [_a-z][_a-zA-Z0-9]*

Constant [A-Z][_a-zA-Z0-9]*
class Klass;end Klass is constant!


Assignment:
a = [1,2,3]

Parallel assignment:
x,y,z,u = a -> x=1,y=2,z=3,u=nil
u,x,y,z = 4,*a -> u=4,x=1,y=2,z=3

Default operator:
port = port || 80 -> if port==nil then port=90
port ||= 80

Guard operator:
port = port && 8080 -> if port!=nil then port=8080
port &&= 8080

Equality:
==,!= -> equality operator
=~,!~ -> pattern-matching operator
"hello"=~/[a-z]+/


Boolean Operator:
&& and
|| or
! not

Conditional:
msg = "you have #{n} #{n==1? "message" : "messages"}"

defined? operator:
y = f(x) if defined? f

Statement & Control Structure

Conditional:
[result = ]if expression [then]
end

[result = ]if expression
elsif
else
end

if/unless as statment modifer:
... if expression
... unless expression

Statement & Control Structure

case:
result = case expression
when ...,... then ...
next
when ...,... then ...
break
else ...
end

Loops:(can be statement modifer)
while expression do
...
end

until expression do
...
end

for var in collection do
...
end

Method,Block,Proc,Lambda

Method Invocation:
puts "hello" -> self,puts,"hello"
Math.sqrt(2) -> Math(Module),sqrt,2
"a".size -> "a",size
[1,2,3].each{|e|...}-> [1,2,3],each, {|e| ...}

object.method(arg1,arg2,...){|a1,a2,..|...}

def object.method(*args,&block)
arg1,arg2,arg3 = *args
block.call(1,2,3...)
end

receiver.send(:private_message,arg1,arg2,...)

Method,Block,Proc,Lambda

Block:
One of the most powerfull feature of Ruby!

[1,2,3].each {|i| ... }
[1,2,3].each do |i|
...
end

def say_hello
print("Jack said:")
yield 1,2 if block_given?
end

say_hello{|a,b| print "hello",a,b} => Jack said:hello12

b = Proc.new{|a,b|print "hello",a,b}
l = lambda{|a,b|print "hello",a,b}
say_hello(&b)
say_hello(&l)

Class

The class keyword in Ruby is more like a scope operator than a
class declaration. the core job is to move you in the context of the
class, where you can deﬁne methods.

Class Constructor:
Class Person
def initialize(name)
@name = name
end
end

Person.new("Jack").name =>
undefined method `name' for #<Person:0x28406f0 @name="Jack"> (NoMethodError)

class Person
def name;return @name;end
def name=(value);@name=value;end
end
class Person
attr_reader :name
end

attr_writer , attr_reader , attr_accessor

Class

Class method(Static function):
Class Person
def Person.class_func
Person
end
def self.class_func ---------
end j methods
end

Method of object(singleton_method):
j = Person.new("jack")

def j.say_hi
puts "hi, i'am jack"
end ???
---------
j say_hi
Define operators:
class Person
def +();end +-*/ Person
def [];end ---------
def <=>;end
end
methods

every time you call a private method,
Class it must be on the implicit receiver—self.

Method Visibility:
class Person
def initialize(name,age)
@name,@age = name,age
end
def introduce
"my name is #{@name},i'm #{@age} years old"
end
protected #every method below will be protected!
def privacy;"my nick name is jacky";end
def secret;end
end
j = Person.new("jack",24)
puts j.introduce
puts j.privacy

class Person
private :privacy #Moduel.private/protected/public
private :secret
end
class Person
private *[:privacy,:secret] #OK!
end
Person.send(:private,:privacy,:secret) #OK!

Class

Make class on-the-fly:
Person = Class.new
[:name,:age].each do |attr|
Person.send(:attr_accessor,attr)
end
Person.send(:define_method,:hi) do
print "I'm #{@name}"
end

class Person
def bye
"bye bye!"
end
end

j = Person.new
j.name = "jack"
j.hi => "I'm jack"
j.bye => "bye bye!"

Class

Inheritance:
class Person;end

class Student < Person
end

s = Student.new
s.class => Student
s.class.class => Class
s.class.superclass => Person
Person.superclass => Object
Student.ancestors => [Student, Person, Object, Kernel]

Module
As namespace:
template<class T>
module Util class Util
PI = 3.14 {
def area public:
self.radius**2 * PI double area() {
end float r = ((T*)this)->radius;
def Util.pi2 return r*r*3.14;
PI**2 }
end };
end class Shape{};
class Pie : public Util<Pie>, public Shape
PI2 = Util.pi2 => 9.8596 {
public:
As mixin: float radius;
Pie():radius(2){}
class Shape;end };

class Pie < Shape #include <iostream>
include Util void main()
def initialize(r);@radius=r;end {
def radius;@radius;end using namespace std;
end Pie p;
cout<<p.area()<<endl;
Pie.new(2).area => 12.56 }

Module

Loading and Requring:

require 'win32/clipboard'
load("c:/a.rb")
load("c:/extension.dll")
load("/home/jack/rb_extension/ext.so")

$LOAD_PATH ($:)
$LOAD_PATH.class => Array
$LOAD_PATH << "d:/my_library"

Reflection & Metaprogramming

Methods:
object.methods
object.private_methods(false)
object.protected_methods
object.public_methods
object.singleton_methods

Variables:
object.instance_variable_defined?
object.instance_variable_get
object.instance_variable_set
object.instance_variables
object.class.class_variables

Parents:
object.superclass
object.ancestors


*eval (evaluate):
eval(string[,bindings])
Klass.class_eval(&block)
Mod.mod_eval(&block)
object.instance_eval(&block)

def object.hi
puts "hi"
end

object.instance_eval do
def hi
puts "hi"
end
end alias :old_method :method
def method(*args,&block)
alias: ...
class Klass old_method(*args,&block)
def hi;puts("hi");end ...
alias :greeting,:hi end
end


method_missing:

class Klass
def method_missing(m)
m.to_s
end
end
k = Klass.new
k.any_thing! => "any_thing!"

const_missing:
class Unicode
def self.const_missing(name)
if name.to_s=~/^U[0-9a-fA-F]{4,5}|10[0-9a-fA-F]{4}$/
codepoint = $1.to_i(16)
utf8 = [codepoint].unpack("U").freeze
const_set(name,utf8)
else
raise NameError,"Uninitialized Constant : Unicode::#{name}"
end
end
end

copyright = Unicode::U00A9 ( ©)

Gems & Rake

Rake:
Make for ruby - Rake
c - make
java - ant
...

Gems: (Jar,Egg)
gem install gem_name
gem uninstall gem_name
gem list --local

parseOpts-0.0.2 net-ssh-2.0.14 mysql-2.8.1-x86 log4r-1.0.5
nokogiri-1.4.1-x86 win32-api-1.3.0 oniguruma-1.1.0 RubyInline-3.8.4
rubyzip-0.9.1 sqlite-2.0.1 Redmine RMagic
wxruby-2.0.1-x86 coderay-0.9.5 ffi-0.5.4-x86 flvtool2-1.0.6
pdf-toolkit-0.5.0 opencv-0.0.6 rubyrss-1.1 *Rails*
FOX，Qt,Tcl/Tk Hpricot .........

Books & Links & Persons

http://www.ruby-lang.org
http://rubyforge.net
https://github.com/languages/Ruby
http://www.sf.net
http://confreaks.net/
http://confreaks.net/presenters/137-dave-thomas
http://www.rubyconf.org/


Programming Ruby by Dave Thomas
The Ruby Programming Language
by David Flanagan and Yukihiro Matsumoto

The Ruby Way 3nd
by Hal Edwin Fulton

Design Patterns in Ruby by Russ Olsen

Ruby Cookbook
by Lucas Carlson and Leonard Richardson

Metaprogramming Ruby by Paolo Perrotta


YUKIHIRO DAVE THOMAS DAVID
MATSUMOTO HEINEMEIER
HANSSON

Ruby Language - A quick tour

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