Download pdf - RedDot Ruby Conf 2014 - Dark side of ruby

The Dark Side of Ruby

@gautamrege!@joshsoftware

What’s the talk about?

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


• Nothing scary


• Nothing scary really


• Nothing scary

• Weirdness and Gotcha’s

really


• Nothing scary

• Weirdness and Gotcha’s

Ah-ha! Moments

really

Slides are Tagged

Slides are Tagged

Beginner

Slides are Tagged

Expert

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

(In)Famous Infinity

(In)Famous Infinity

(In)Famous Infinity$ irb> 1/0

(In)Famous Infinity$ irb> 1/0=> ZeroDivisionError: divided by 0


$ irb> 1.0/0

=> ZeroDivisionError: divided by 0


$ irb> 1.0/0


=> Infinity


$ irb> 1.0/0

$ irb> Infinity


=> Infinity


$ irb> 1.0/0

$ irb> Infinity


=> Infinity

=> NameError: uninitialized constant Infinity

(In)Famous Infinity

(In)Famous 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;

(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

Base Conversions

Base Conversions$ irb> 12345.to_s(8)

Base Conversions$ irb> 12345.to_s(8)=> "30071" # => Octal


$ irb> 12345.to_s(36)

=> "30071" # => Octal


$ irb> 12345.to_s(36)

=> "30071" # => Octal

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


$ irb> 12345.to_s(36)

$ irb> 1234.to_s(64)

=> "30071" # => Octal



$ irb> 12345.to_s(36)

$ irb> 1234.to_s(64)

=> "30071" # => Octal


=> ArgumentError: invalid radix 64

Hashes and Arrays

Hashes and Arrays

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

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


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

[1,2,3] * "%"


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

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

Calling out to Stabby

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


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


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

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


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

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


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

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

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


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

Syntax

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

end

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

end

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

endkeyword arguments

Syntax

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

end

def foo(a: 1, b: 2)


Syntax

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

end

def foo(a: 1, b: 2)


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)


Syntax

Syntaxdef foo(a, b) p a, b

end


end

foo (1, 2)


end

foo (1, 2)syntax error, unexpected

',', expecting ')'


end

foo (1, 2)

foo(1, 2)


end

foo (1, 2)

foo(1, 2)


end

foo (1, 2)

foo(1, 2) syntax error, unexpected ',', expecting ')'

Syntax

Syntaxirb> a[1]

What is the data type of a ?

Syntaxirb> a[1]

a = [ 10, 11, 12] # Array

Syntaxirb> a[1]

a = [ 10, 11, 12] # Array

a = { 1 => "one" } # Hash

Syntaxirb> a[1]

a = [ 10, 11, 12] # Array

a = { 1 => "one" } # Hash

a = Proc.new { |e| p e }

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

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



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/

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

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

==, ===, eql?, equal?irb> 1 == 1.0

==, ===, eql?, equal?irb> 1 == 1.0=> true # generic equality

==, ===, eql?, equal?irb> 1 == 1.0=> true # generic equalityirb> 1 === 1.0

==, ===, eql?, equal?irb> 1 == 1.0=> true # generic equalityirb> 1 === 1.0=> true # case equality

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

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

=> false # alias of == except Numeric

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

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



irb> 1.equal? 1.0

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



irb> 1.equal? 1.0=> false # object identity

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



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

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


=> false # gotcha?



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


=> false # gotcha?



irb> 1.equal? 1

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


=> false # gotcha?



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

Object Ids & Fixnum

Object Ids & Fixnum

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

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/

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

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 Hell- Pink Floyd

So! So you think you can tell…

Protected from Private

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



Private Methods are inherited!

class Base! include Mongoid::Document!end

The elusive include


The elusive include

Private method!Instance method !

Defined the class Module


The elusive include

Protected methods

Protected methods

Protected methods

• Work with objects not classes.

Protected methods


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

Protected methods


• 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"


"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 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 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!"

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


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


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


Cherry pick from Modules

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

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


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!


class Hanuman! include Megatron!end

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


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

That’s all Folks!

@gautamrege @joshsoftware

since 2007