Zero to Ruby
Samnang Chhun
@samnangchhun
:about_me => {
:name => "Samnang Chhun",
:work_at => ["Yoolk Inc.", "Freelancer"],
:website => "http://wowkhmer.com",
:email => "[email protected]",
:twitter => "@samnangchhun",
:certificattions => ["MCTS"],
:communities => [
"Ruby Mendicant University",
"RubyLearning",
"ShareVisionTeam",
"Pailin"
]
}http://tryruby.org
let students test with code snippets on http://tryruby.org
"I love Ruby" * 5
5.times { puts "I love Ruby" }
[1, 3, "samnang"].last.capitalizeWhy Ruby?
- Because Matz loves Ruby :-)
- Dynamically typed language
- An 100% OO language (well, 99.9%)
- Concise. Simple. Fun!
- Open source
- Ruby makes developers have fun.
Ruby Implementations
- MRI, YARV
- JRuby
- Rubinius
- IronRuby
- MacRuby
- etc.
Ruby version
$ ruby -v
ruby 1.9.2p180 (2011-02-18 revision 30909) [x86_64-darwin10.7.0]
Interactive Ruby Shell
$ irb
ruby-1.9.2-p180 :001 > puts "I love Ruby!"
I love Ruby!
=> nil
let students test codes in irb
"I love Ruby" * 5
5.times { puts "I love Ruby" }
[1, 3, "samnang"].last.capitalizeConfigure and extend irb
- .irbrc irb's configration
- Auto completion
- Simple Mode
- plugins or gems(looksee, interactive_editor, ...)
- Customize by yourself
Using Ruby's documentation
- http://rubydoc.info/stdlib
- http://apidock.com/ruby/
- ri (Ruby Index)
- irb (sometimes it helps as well)
Ruby Core
Simplicity
5.times { print "Ruby! "}
print "Ruby! " * 5
100.next
'a'.next
1.upto(5) {|x| puts x }
5.downto(1) { |x| puts x }Almost everything in Ruby is an object
100.next #=> 101
'a'.next #=> "b"
100.class #=> Fixnum
"Ruby".class #=> String
[].class #=> Array
{}.class #=> Hash
5.times { print "Ruby! " }
#=> Ruby! Ruby! Ruby! Ruby! Ruby!
5 + 5
5.+(5) # both are the sameArray
numbers = ['zero', 'one', 'two', 3]
numbers[0] #=> 'zero'
numbers.first #=> 'zero'
numbers.last #=> 3
numbers[-1] #=> 3
list = []
list << 'first'
list << 'bar'
list.pop # can be used as a stackHash
profile = {
:name => "Samnang",
:age => 100 #Who knows :-)
}
profile[:name]
profile[:age]Range
range = 1..5
range.to_a #=> [1, 2, 3, 4, 5]
range = 'a'..'z'
range.to_a # array of strings from a to z
range = 1...5
range.to_a #=> [1, 2, 3, 4]
range.include? 2 #=> true
array = [1, 2, 3, 4]
array[0..2] #=> [1, 2, 3]
array[1...-1] #=> [2, 3]Conditionals and Iterators
if something_true?
do_something
else
do_another_thing
end
puts "I'll love Ruby" if not absence_today?
puts "I'll love Ruby" unless absence_today?
%w{Ruby HTML5 CSS3}.each do |lang|
puts "#{lang} is so cool!"
endRuby package
see some classes on both ruby core and standard library
Ruby Core Classes
(String, Fixnum, Array, ...)
Ruby Standard Library
(CSV, ERB, Webrick, ...)
Exercise
Ruby Object Model
Classes
class BankAccount
attr_accessor :name, :account_no
attr_reader :balance
def initialize(name)
@name = name
@balance = 0
end
def deposit(amount)
@balance += amount
end
def withdraw(amount)
@balance += amount
end
def active?
#is account active or not
end
end
account = BankAccount.new("Samnang")Inheritance
class Animal
# ...
end
class Cat < Animal
# ....
end
class Dog < Animal
# ...
endMixins
module A
def say_hello
puts "Hello"
end
end
module B
def say_goodbye
puts "Goodbye"
end
end
class C
include A
include B
end
obj = C.new
obj.say_hello
obj.say_goodbyeNamespaces
module XML
class Parser
# ...
end
end
module PDF
class Parser
# ...
end
end
XML::Parser
PDF::ParserSingleton Methods
animal = "cat"
another_aminal = "dog"
def animal.speak
puts "The #{self} says miaow"
end
animal.speak # The cat says miaow
another_animal.speak
# NoMethodError: undefined method `speak' for "dog":StringObject model for a basic class
Singleton class involved
demo how to access singleton class in Ruby 1.8 and Ruby 1.9
Singleton classes
(Eigenclasses/Metaclasses/Virtual Classes/Ghost classes)
- It's an anonymous class that you can't instantiate object from it
- It's hidden
- It is created automatically by the interpreter when you refer to it at the first time
- Except from those above, it works like normal classes
self (current object)
- Read-only variable
- Has 2 significant roles in a running Ruby program:
self controls how Ruby finds instance variables.
self plays a vital role in method calling.
Understanding Ruby's method lookup
- Find out what is self in current line of executing program
- Ruby methods are looked up in the following order:
Ruby methods are looked up in the following order
- Methods defined in the object's singleton class (i.e. the object itself)
- Modules mixed into the singleton class in reverse order of inclusion
- Methods defined by the object's class
- Modules included into the object's class in reverse order of inclusion
- Methods defined by the object's superclass.
Example
Duck Typing
If it walks like a duck, and talks like a duck,Then we can treat it like a duck. (who cares what it really is)
Duck Typing
- In Ruby, we rely less on the type (or class) of an object and more on its capabilities.
- Duck Typing means an object type is defined by what it can do, not by what it is.
class Duck
def quack
puts "Quack!"
end
end
class DuckRecording
def quack
play
end
def play
'Quack!'
end
end
[Duck.new, DuckRecording.new].each { |a| a.quack }Monkey Patching
- Objects and class are open:
add / override method to object even at Runtime! - Might be dangerous or break some stuff:
but its awesome
class Array
def second
self[1]
end
end
[1, 2, 3].second # => 2
require 'active_support/core_ext'
2.days.from_now # => 2011-06-20 14:14:11 +0700
"person".pluralize # => "people"Basic metaprogramming and DSL
Metaprogramming
- Wikipedia: "Metaprogramming is the writing of computer programs that write or manipulate other programs (or themselves) as their data, or that do part of the work at compile time that would otherwise be done at runtime."
- Code that writes code.
Example
class Person
attr_accessor :name, :age
endGetters and Setters from Java style
class Person
def name
@name
end
def name=(value)
@name = value
end
def age
@age
end
def age=(value)
@age = value
end
endThen change it into
class Person
%w(name age).each do |method_name|
define_method(method_name) do
instance_variable_get("@#{method_name}")
end
define_method("#{method_name}=") do |value|
instance_variable_set("@#{method_name}", value)
end
end
endFinally
class Person
attr_accessor :name, :age
endDomain Specific Language(DSL)
Martin Fowler: The basic idea of a domain specific language (DSL) is a computer language that's targeted to a particular kind of problem, rather than a general purpose language that's aimed at any kind of software problem. Domain specific languages have been talked about, and used for almost as long as computing has been done.
Two kinds of DSL
Internal DSL
use a host language to give the host language the feel of a particular language.
External DSL
have their own custom syntax and you write a full parser to process them.
demo some codes
Examples of internal DSL
- RSpec
- Capybara
- Sinatra
- ...
Examples of external DSL
- Cucumber
- Haml
- SQL
- CSS
- ...