Ruby for Java minds - Speaker Deck

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RUBY FOR JAVA MINDS

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$ whoami

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@janogonzalez

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@hop_in

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HISTORY

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THE 90’S

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BIG CHANGES

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COLD WAR IS OVER

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GRUNGE GOES MAINSTREAM

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APATHY

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SELF- ALIENATION

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ANGST IS THE NEW COOL

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MEANWHILE IN THE PROGRAMMING WORLD...

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RAISING AGAINST THE MAINSTREAM

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JAMES GOSLING

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JAMES GOSLING

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JAVA

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“Write Once, Run Anywhere”

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THE 5 PRINCIPLES • It should be "simple, object-oriented and familiar" • It should be "robust and secure" • It should be "architecture-neutral and portable" • It should execute with "high performance" • It should be "interpreted, threaded, and dynamic"

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(THAT WAS NOT RSPEC)

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MATZ

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MATZ

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RUBY

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“Ruby is designed to make programmers happy”

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MATZ WINS THE NOBEL PEACE PRICE

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(HISTORICAL ACCURACY IS OVERRATED)

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2 DIFFERENT PHILOSOPHIES

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HOW DO WE EMBRACE RUBY?

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MY HISTORY

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Y2K

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COMPUTER APOCALYPSE DID NOT HAPPEN

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I WENT TO A “JAVA SCHOOL”

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JAVA EE, SPRING AND CUBICLES

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HEY, RAILS LOOK COOL!

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HEY, THERE IS A FLY OVER THERE!

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(STUPID FLY)

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THE 10’S

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RAILS VS JAVA EE WAS OVER

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HEY, RUBY LOOKS COOL!

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WAIT, HOW DO I DECLARE AN INTERFACE?

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THE PROBLEM

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“The determined Real Programmer can write FORTRAN programs in any language.” –Ed Post

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HOW TO WRITE RUBY THAT FEELS LIKE RUBY?

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A ZEN MOMENT

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ॳ৺

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BEGINNER’S MIND

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EMPTY YOUR CUP

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BACK TO BASICS

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THE KEY TO UNDERSTAND RUBY

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EXPRESSIONS + OBJECTS

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SYNTAX IS EXPRESSION-ORIENTED

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“LISP programmers know the value of everything and the cost of nothing.” - Alan Perlis

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EXPRESSIONS def average(a, b) (a + b) / 2 end # => nil average(10, 2) # => 6

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EXPRESSIONS level = case when 1..2 then :excellent when 3..5 then :normal else :bad end

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ALL VALUES ARE OBJECTS

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OBJECTS -1.class # => Fixnum

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OBJECTS String.object_id # => 70138854779960

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OBJECTS nil.nil? # => true

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WO IST DEIN GOTT JETZT

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MESSAGES

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MESSAGES EVERYWHERE

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MESSAGES 40 + 2 # => 42

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MESSAGES 40.+(2) # => 42

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MESSAGES 40.send(:+, 2) # => 42

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MESSAGES ≠ METHODS

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MESSAGES class AccountProtectionProxy def initialize(real_account, owner) @subject = real_account @owner = owner end ...

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MESSAGES class AccountProtectionProxy ... def method_missing(name, *args) check_access @subject.send(name, *args) end ... end

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DYNAMIC TYPING

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FORGET ABOUT JAVA INTERFACES

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JAVA public interface Report { ReportFile generate(); }

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JAVA public class PDFReport implements Report { .... }

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JAVA public class CSVReport implements Report { .... }

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JAVA public void print(List reports) { if (reports == null) { return; } for (Report r : reports) { ReportFile file = r.generate(); ... } }

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DYNAMIC TYPING def print(reports) [*reports].each do |r| file = r.generate ... end end

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DYNAMIC TYPING class PDFReport def generate ... end ... end

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DYNAMIC TYPING class CVSReport def generate ... end ... end

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DYNAMIC TYPING class Duck def generate ... end ... end

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PROGRAM TO INTERFACES, NOT TO interface

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USED EVERYWHERE

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DYNAMIC TYPING "Jano in " << "Berlin" # => "Jano in Berlin" ["Santiago"] << "Berlin" # => ["Santiago", "Berlin"]

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IF YOU REALLY NEED TO CHECK...

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DYNAMIC TYPING if report.respond_to?(:generate) report.generate ... else ... end

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IF YOU REALLY, REALLY NEED TO CHECK...

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DYNAMIC TYPING if report.is_a?(Report) report.generate ... else ... end

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DYNAMIC BUT NOT WEAK

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STRONG TYPING 100 + 'cool' # TypeError: String can't be coerced into Fixnum

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TYPE CONVERSIONS

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CONVERSIONS 100 + 'cool'.to_i # => 100 100 + Integer('cool') # ArgumentError: invalid value for Integer(): "lala"

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BLOCKS

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BLOCKS ARE USED & ABUSED IN RUBY

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PROGRAM LIKE A BOSS

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(LITERALLY)

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BLOCKS (1..100).select { |n| n % 3 == 0 } .map { |n| n * 2 } .reduce(:+)

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FLUID CODE

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BLOCKS File.open('my.txt').each do |line| puts line if line =~ /jano/ end

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BE MORE DECLARATIVE

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BLOCKS words.sort do |a, b| a.length <=> b.length end words.min_by? { |w| w.length } words.reject { |w| w.length > 8 } # etc...

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EXAMPLE: SELF YIELD

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BLOCKS class Job def initialize yield self if block_given? end ... end

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BLOCKS job = Job.new do |j| j.name = 'Print Reports' j.user = 'janogonzalez' ... end

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EXAMPLE: CALLBACKS

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BLOCKS class Job def on_finish(&block) @end_callback = block end def execute() ... @end_callback.call(self) if @end_callback end end

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BLOCKS job.on_finish do |j| puts "Finished job #{j.name}" puts "Status: #{j.status}” end

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MIXINS

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MODULES AS MIXINS

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ADD BEHAVIOR TO INSTANCES

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MODULES module Model def persist ... end end

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MODULES class User include Model ... end

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MODULES job = User.new('Jano') job.persist

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ADD BEHAVIOR TO CLASSES

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MODULES module Findable def find_by_id(id) ... end end

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MODULES class User extends Findable ... end

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MODULES user = User.find_by_id(3)

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METAPROGRAMMING

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(USE WITH CAUTION)

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(AKA THE EVAL IS EVIL RULE)

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ACCESSORS

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ACCESSORS class User attr_reader :name attr_reader :status end

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OPEN CLASSES

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OPEN CLASSES class Range def even select(&:even?) end end (0..10).even # => [2, 4, 6, 8, 10]

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OPEN CLASSES class BuggyClass def buggy_method # the fix ... end end

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OPEN CLASSES class Job alias_method :old_execute, :execute def execute ... old_execute end end

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DEFINE METHODS

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DEFINE METHODS obj = User.new User.class_eval do def represent ... end end obj.represent

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DEFINE METHODS User.instance_eval do def random ... end end User.random

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SINGLETON METHODS

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SINGLETON METHOD obj = Person.new class << obj def represent ... end end obj.represent

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(A LOT MORE TO EXPLORE...)

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ONE LAST ADVICE

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कഁ཭

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SHU कഁ཭

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HA कഁ཭

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RI कഁ཭

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CONCLUSIONS

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EMBRACE DYNAMIC TYPING

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BE MORE DECLARATIVE

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WRITE LESS DO MORE

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CONVENTIONS AND IDIOMS ARE NOT LAWS

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THERE IS NO TRUE PATH

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ENJOY RUBY! (AND JAVA TOO)

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DANKESCHÖN!

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¡MUCHAS GRACIAS!

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IMAGES • http://006.shanbara.jp/movie/data/fat1367385194099.jpg • http://wﬁles.brothersoft.com/n/nirvana-desktop_157301-1600x1200.jpg • http://stilestili.com/wp-content/uploads/2013/04/Ryan- Gosling2-2048x2560.jpg • http://upload.wikimedia.org/wikipedia/commons/thumb/1/14/ James_Gosling_2008.jpg/1018px-James_Gosling_2008.jpg • http://www.ﬂickr.com/photos/john_lam/1910968816/