RubyAslak Hellesøy / Øystein Ellingbø

Consulting

Yukihiro “Matz” Matsumoto

1993-02-24: Matz starts hacking on Ruby

1995-12-21: Matz released Ruby on fj.sources

1999: First book in Japanese

2000: First book in English

Ruby

Sapir-Whorf HypothesisPeople who speak different languages perceive and think about the world quite differently

People's thoughts are determined by the categories made available by their language

Differences among languages cause differences in the thought of their speakers

Any language that does change the way you think about programming isn't worth learning

Sortering i Java

Sortering i Ruby

Ruby implementations

• MRI• YARV• JRuby• Rubinius• IronRuby• MagLev• MacRuby

Standard libraryRubyForgeIrbRiRDocRakeRubyGemsRSpecTest::UnitRCovDebugger

Object Oriented

• In Ruby, Everything is an Object

• No Primitives

• A few (seemingly) global functions

• great for scripting ...

• FUN

Scripting Language

• Interpreted, not compiled

• Slower execution

• Faster development

• Implicit ‘main’ method

# hello.rbputs "Hallo NTNU!"

$ ruby hello.rbHallo NTNU!$

Coding Conventions def hello_world my_message = "Hi" puts my_messageend

• Two-space indentation

• No tabs

• Snake case (mostly)

Variables

ClassNameTHIS_IS_A_CONSTANTlocal_variable$global_variable@instance_variableregular_methodquestion_method?dangerous_method!

Variables

ClassNameTHIS_IS_A_CONSTANTlocal_variable$global_variable@instance_variableregular_methodquestion_method?dangerous_method!

Everything is an Object# Classes are objectshash = Hash.new

# Numbers are objects-1.abs # => 1

# Even nil is an objecta = nila.nil? # => true

Classesclass MyClassend

o = MyClass.newputs o# #<MyClass:0x355e94>

Methodsclass MyClass def hello(name) "Hi, #{name}" endend

o = MyClass.newputs o.hello("Bob") # Hi, Bob

Operators are methods

2 + 2

2.+(2)

list << 'a'

list.<<('a')

x == 5

x.==(5)

Method argumentsdef no_argsend

def two_args(foo, bar)end

def varargs(foo, *bar) puts bar.class # => Arrayend

def with_proc(foo, &proc) proc.call("Chunky", "bacon!")end

Method Signatures

def weirdo(x) if x == 5 "Bingo" else 23 endend

puts weirdo(5) # => "Bingo"puts weirdo("Sponge") # => 23

Dynamic Typing

def quack_it(o) o.quackend

quack_it(duck) # OK, Duck has a quack methodquack_it(horse) # NoMethodError: undefined method 'quack'

a = 'hi'a = [] # a's type is carried by the valueputs a.class # => Array

"x" + 5 # TypeError: can't convert Fixnum into String

It is still Typing• Objects are still strongly typed

• You can not tell an object to be another type

• But you can tell a variable to point to an object of a different type

• You can ask an object its type

• But don’t

• Instead, ask what it can do

Open Classes

Add Behaviour to Existing Classes

class Object def introduce_thyself "Hello, I am an instance of #{self.class}" endend

puts "NDC".introduce_thyself# => Hello, I am an instance of String

puts 5.introduce_thyself# => Hello, I am an instance of Fixnum

puts lambda {}.introduce_thyself# => Hello, I am an instance of Proc

#1 Åpne klasserputs 5.even?puts 8.even?# false# true

require 'rubygems'require 'activesupport'

puts 2.days.ago

$ ruby days.rbSat Jun 14 13:55:51 +0200 2008

Collections# Arraya = [2, 3, 5]puts a[1] # => 3a << 6puts a[-1] # => 6

# Hashh = {'x' => 99, 'y' => 98}puts h['y'] # => 98h[1] = 'y'puts h[1] # => 'y'

# Ranger = 4..9puts r.to_a.inspect# [4, 5, 6, 7, 8, 9]

Iterators

a = [2, 3, 5]a.each do |e| puts eend# 2# 3# 5

a = [2, 3, 5]b = a.map do |e| e * eend

puts b.inspect # [4, 9, 25]

h = {'x' => 99, 'y' => 98}h.each do |k, v| puts "#{k} => #{v}"end# x => 99# y => 98

print_down_to_0(5)# 5# 4# 3# 2# 1# 0

#2 Traversering

Strings

s = "A String"puts s # => A Stringputs s.object_id # => 9428360

s.gsub!("ing","and")puts s # => A Strandputs s.object_id # => 9428360

• Similar “feel” to Java and C#, except

• Mutable

• No Unicode (getting there)

Symbols

x = :fooy = :foo

puts x.equal?(y) # object identity# => true

• Immutable Strings

• Mostly used as keys in hashes

• Flyweight

Metaprogrammerin

def method_missing(name, *args)end

r = ReverseAnything.newputs r.olleh# hello

#3 method_missing

Blocks / yielddef i_yield yield 'hi'end

i_yield do |what| puts whatend# hi

def i_yield(&proc) proc.call('hi')end

(1...10).each_even do |e| puts eend# 2# 4# 6# 8(1...10).each_even { |e| puts e }

#4 yielding

module Happiness def happy? true endend

class RubyDeveloper include Happinessend

Modules

module Awesome class Stuff endend

s = Awesome::Stuff.new

Namespaces

Regular Expressions

• Find words and patterns in strings

• Validation

• Extract substrings

• Used heavily in Ruby, Perl, Python and Javascript

• \b[A-Z0-9._%+-]+@[A-Z0-9.-]+\.[A-Z]{2,4}\b

String text = "Aslak is 181cm tall"; Pattern p = Pattern.compile("(\\d+)cm"); Matcher m = p.matcher(text); if(m.find()) { System.out.println(m.group(1)); }

Java

text = "Aslak is 181cm tall"if text =~ /(\d+)cm/ puts $1end

Ruby

Regular ExpressionsString text = "Aslak is 181cm tall";MatchCollection m = Regex.Matches(text, @"(\d+)cm");if (m.Success){ Console.WriteLine(m[0].Groups[1].Value);}

C#

Resources

http://ruby-lang.org/http://rubyforge.org/http://rubyquiz.com/

http://tryruby.hobix.com/+ thousands of blogs and lists