Ruby Presentation - Article

Ruby: Why We Love It
https://github.com/Kelsin/ruby-presentation
Christopher Giroir
November 8th, 2011
Contents
1 The Language 1
1.1 Basics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
1.2 Why We Love It . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.3 Gems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Tools 6
2.1 Bundler . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.2 RVM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
1 The Language
1.1 Basics
Overview
• Inspired by Smalltalk (which I love)
• Also draws from Perl, Eiﬀel, Ada and LISP
• Includes a REPL
• Built for developers as a language they would love to use
• Dynamic, strict, reﬂective, object oriented
• Everything is an expression (even statements)
• Everything is executed imperatively (even declarations)
Object Oriented
• Everything is an object
• Single Inheritance
• Modules can be mixed in
• Dynamic Dispatch
1

Simple Code
1 5.times { print "Hello" }
This outputs:
1 Hello
2 Hello
3 Hello
4 Hello
5 Hello
6 => 5
Types
1 # Strings
2 s = ’Testing’
3
4 # Interpreted Strings
5 t = "Double #{str}"
6
7 # Symbols
8 sym = :chris
9
10 # Arrays
11 a = [1,2,3]
12
13 # Hashes
14 h = { :key => ’value’, :chris => ’awesome’ }
Classes
1 class Box
2 def initialize(w,h,d)
3 @width = w
4 @height = h
5 @depth = d
6 end
7
8 def volume
9 @width * @height * @depth
10 end
11 end
12
13 box = Box.new(2,2,2)
14 box.volume # => 8
Simple Inheritance
1 class JackInTheBox < Box
2 def initialize(msg)
3 @msg = msg
2

4 super(3,3,3)
5 end
6
7 def open
8 puts @msg
9 end
10 end
11
12 jbox = JackInTheBox.new(’Surprise!’)
13 jbox.volume # => 27
14 jbox.open # prints ’Surprise!’
Control
1 while true == false
2 if var == 5
3 break
4 end
5
6 begin
7 var - 1
8 end while var < 4
9
10 next if var == 6
11 end
Blocks
1 [1,2,3].each { |n| puts n }
This outputs:
1 1
2 2
3 3
4 => [1,2,3]
Block Syntax
1 5.upto(10) { |n| puts n }
This is exactly the same as the following:
1 5.upto(10) do |n|
2 puts n
3 end
1.2 Why We Love It
Attribute Methods
3

1 class Person
2 def name
3 @name
4 end
5 def social=(s)
6 @social = s
7 end
8 def age
9 @age
10 end
11 def age=(a)
12 @age = a
13 end
14 end
The Easy Way
1 class Person
2 attr_reader :name
3 attr_writer :social
4 attr_accessor :age
5 end
The Easy Way Explained
1 class Person
2 attr_reader :name
3 attr_writer :social
4 attr_accessor :age
5 end
• Ruby syntax allows method calls without ()
• Result is clean and looks like a language feature
• We can implement this ourselves
• Untested code, please do not copy:
1 class Object
2 def self.attr_reader(var)
3 class_eval <<-METHODS
4 def #{var}
5 @#{var}
6 end
7 METHODS
8 end
9 end
Why Blocks
1 (map (lambda (n)
2 (+ n 5))
3 ’(1 2 3))
4

Becomes:
1 [1,2,3].map do |n|
2 n + 5
3 end
Results in:
1 => [6,7,8]
1.3 Gems
Modules
1 module Voice
2 def say(msg)
3 puts msg
4 end
5 end
6
7 class Person
8 include Voice
9 end
10
11 p = Person.new
12 p.say(’Hello’) # prints ’Hello’
Using Gems
Require loads in ﬁles
1 require ’saver’ # pulls in ’saver.rb’
Gems allow us to not deal with paths
1 require ’rubygems’
2 require ’saver’
3
4 class Item
5 include Saver
6 end
Writing Gems
1 Gem::Specification.new do |s|
2 s.name = "saver"
3 s.version = Saver::VERSION
4 s.authors = ["Christopher Giroir"]
5 s.email = ["kelsin@valefor.com"]
6 s.homepage = "http://kelsin.github.com/saver/"
7
8 s.files = ‘git ls-files‘.split("n")
9 s.require_paths = ["lib"]
10
11 s.add_dependency ’activesupport’, ’~> 3.0.0’
12 s.add_dependency ’mongo_mapper’
13 end
5

2 Tools
2.1 Bundler
Why Bundler?
• Many projects (i.e. rails apps) are not gems themselves
• They do have gem dependencies
• Easy way to install and keep track of these dependencies
• Making sure ONLY the proper gems are used
The Gemfile
1 source ’http://tools1.savewave.com/rubygems’
2 source ’http://rubygems.org’
3
4 gem ’rails’, ’3.0.7’
5
6 gem ’sw-model’, ’0.13.0’
7
8 group :development, :test do
9 gem "rspec"
10 end
Using Bundler
1 # Install the gems from the Gemfile
2 bundle install
3
4 # Update gems to new versions
5 bundle update
6
7 # Execute command with proper gems
8 bundle exec rake spec
In your ruby code
1 require "rubygems"
2 require "bundler/setup"
3 require "saver"
Gemfile.lock
• When you initially install versions are saved to Gemfile.lock
• After they are only updated on bundle update
• SHOULD be checked into version control
• Protects from version updates
6

2.2 RVM
Why RVM?
• Different projects might use different versions of rails
• Different projects might use different ruby interpreters
– Ruby
– JRuby
– Rubinus
• While bundler helps, complete gem isolation is better!
• It’s nice to keep your system ruby separate and not update it
Using RVM
1 # Install the default 1.9.2 ruby interpretor
2 rvm install 1.9.2
3
4 # Switch to using 1.9.2
5 rvm use 1.9.2
6
7 # List installed rubies
8 rvm list
RVM Gemsets
1 # Create a new gemset
2 rvm gemset create savingstar-web
3
4 # List gemsets
5 rvm gemset list
6
7 # Switch to a ruby and gemset together
8 rvm use 1.9.2@savingstar-web
.rvmrc
• A .rvmrc file per project allows you to say which ruby and gemset to use
• Should be in source control. Helps RVM users out, ignored for others
• It’s a shell script that’s executed everytime you cd (very unsafe)
• Makes life very easy however!
1 rvm use 1.9.2@saveingstar-web --create
7

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