The Dark Side of Ruby

@gautamrege!@joshsoftware

What’s the talk about?• Ruby is AWESOME but …

• Nothing scary

• Weirdness and Gotcha’s

Ah-ha! Moments

really

Slides are Tagged

BeginnerExpert

(In)Famous Infinityhttp://www.flickr.com/photos/emdot/482622478/sizes/l/

(In)Famous Infinity$ irb> 1/0

$ irb> 1.0/0

$ irb> Infinity

=> ZeroDivisionError: divided by 0

=> Infinity

=> NameError: uninitialized constant Infinity

(In)Famous Infinity#if !defined(INFINITY) || !defined(NAN)!union bytesequence4_or_float {! unsigned char bytesequence[4];! float float_value;!};!#endif!!RUBY_EXTERN const union bytesequence4_or_float rb_infinity;

include/ruby/missing.h

Base Jumping

http://www.flickr.com/photos/shahdi/8035647153/sizes/l/

Base Conversions$ irb> 12345.to_s(8)

$ irb> 12345.to_s(36)

$ irb> 1234.to_s(64)

=> "30071" # => Octal

=> "9ix" # That is an actual number

=> ArgumentError: invalid radix 64

Splat ExpanderJob = Struct.new(:name, :occupation) tom = Job.new("Tom", "Developer") name, occupation = *tom

=> ["Tom", "Developer"] => name # "Tom" => occupation # "Developer"

Splat ExpanderJob = Struct.new(:name, :occupation) tom = Job.new(occupation: "Developer", name: "Tom") name, occupation = *tom

=> name # {:occupation=>"Developer", :name=> "Tom"} => occupation # nil

Hashes and Arraysa=[1,2,3,4,5,6]!h=Hash[*a]=> {1=>2, 3=>4, 5=>6}

[1,2,3] * 3!=> [1,2,3,1,2,3,1,2,3]

[1,2,3] * "%"!=> "1%2%3"

blk.(1, 2, 3, 4, 5, 6)=> 5

syntax sugar for call blk[1,2,3,4,5,6]

Calling out to Stabbyblk = ->(f, *m, sl, l) do puts sl end

blk.call(1, 2, 3, 4, 5, 6) => 5

Syntax

def foo(a: 1, b:, c: 2)

end

foo(a: 2) => ArgumentError: missing keyword: b

Mandatory keyword arguments

def foo(a: 1, b: 2)

endkeyword arguments

def foo(a=1, b=1,opts={})

end

Case Complexity

The Case Statementdef multiple_of(factor)! Proc.new {|p| p.modulo(factor).zero?}!end!!

number = 9!case number! when multiple_of(3)! puts "Multiple of 3"! when multiple_of(7)! puts "Multiple of 7"!end

Behind every case is a ===number = 9!case number ! when multiple_of(3)

Proc.new {|p| p.modulo(3).zero?} === 9

Proc.new { |p| ! p.modulo(3).zero?!}.call(9)

Proc#=== is an alias to Proc#call.

Override the === method to customise case

evaluation.

==, ===, eql?, equal?

http://www.flickr.com/photos/gak/2418146934/sizes/o/

==, ===, eql?, equal?

=> false # equality by value

=> false # gotcha?

irb> 1 == 1.0=> true # generic equalityirb> 1 === 1.0=> true # case equalityirb> 1.eql? 1.0

irb> 1.equal? 1.0=> false # object identityirb> 'a'.equal? 'a'

=> true # gotcha?irb> 1.equal? 1

Object Ids & Fixnum

Fixnum * 2 + 1irb> 23 * 2 + 1 => 47 irb > 23.object_id => 47

irb> (2**62 - 1).class => Fixnum irb> (2**62).class => Bignum

http://www.flickr.com/photos/miscdebris/6748016253/sizes/o/

3 Pulls for the Jackpotjackpot = lambda { |x, y, z| (x == y) == (x == z) } # 3 pulls pull = jackpot.curry[rand(5)] 2.times { pull = pull.curry[rand(5)] } !

p pull ? "Jackpot" : "Sucker!"

The curry recipe

• Return lambda till all parameters are passed.

• Evaluate the block if all parameters are passed.

pull = jackpot.curry[rand(5)] => #<Proc:0x007f9eec0990b0 (lambda)>

2.times { pull = pull.curry[rand(5)] } => true # or false

So! So you think you can tell…

Heaven from HellProtected from Private- Pink Floyd

Private methodsclass Soldier private def ryan puts "inside private ryan" end end class Movie < Soldier def name ryan end end

Private Methods are inherited!

Private method!Instance method !

Defined the class Module

class Base! include Mongoid::Document!end

The elusive include

Protected methods

• Work with objects not classes.

• Invoke a protected method on another object in the same lineage

What the …

class Autobot def initialize(nick); @nick = nick; end !

protected attr_accessor :nick end !prime = Autobot.new("Optimus Prime") p prime.nick

protected method `nick' called for #<Autobot:0x007f92ba082330 @nick="Optimus Prime"> (NoMethodError)

class Autobot def fights(target) p "I am #{self.nick}" p "Kicking #{target.nick}'s ass" end protected attr_accessor :nick end !optimus = Autobot.new("Optimus Prime") megatron = Autobot.new('Megatron') !optimus.fights megatron

"I am Optimus Prime" "Kicking Megatron's ass"

Keywords in Ruby?

Keywords - hmm…class Serious def true false end def false true end end die = Serious.new p "seriously!" if die.false

stack too deep?

superlativeclass Search! def search! p "Default Search algorithm"! end!end!class KeywordSearch < Search ! def search(keyword:)! super! end!end!KeywordSearch.new.search(keyword: "Ruby")

`search`: wrong number of arguments (1 for 0)

superlativeclass Search! def search! p "Default Search algorithm"! end!end!class KeywordSearch < Search ! def search(keyword:)! super()! end!end!KeywordSearch.new.search(keyword: "Ruby")

And we thought parenthesis for method invocation didn’t matter

Module mixins are funnymodule Superman! def fly; p "Superman: It's a bird"; end!end!!module Batman! def fly; p "Batman: Fly? Me?"; end!end!!module Ironman! def fly; p "Iroman: That's flying!"; end!end

Module mixins are funnyclass Tinyman! include Superman! include Batman! include Ironman!end!!Tinyman.new.fly

"Iroman: That's how you fly!"

Module Inheritance?module Superman! def fly; p "Superman: It's a bird"; end!end!!module Batman! def fly; p "Batman: Fly? Me?"; end!end!!module Ironman! def fly; super; p "Iroman: That's flying!"; end!end

"Batman: Fly? Me?”!"Iroman: That's flying!"

class Tinyman! include Superman! include Ironman! include Batman!end

Dynamic Inheritance!class Tinyman! include Superman! include Batman! include Ironman!end

Cherry pick from Modules

module Megatron! def power! p "Megatron's super strength"! end!!

def evil! p 'Evil genius'! end!end

class Hanuman! include Megatron!end

Hanuman.new.power!# => "Megatron's super strength"!Hanuman.new.evil !# => "Evil genius" # Oh no!

Cherry pick from Modules

Cherry pick from Modulesclass Hanuman! def power! Megatron.instance_method(:power).! bind(self).call! end!end

Hanuman.new.power!# => "Megatron's super strength"!Hanuman.new.evil !# => undefined method `evil’...>

That’s all Folks!

@gautamrege @joshsoftware

since 2007