gcrc 2014 - the dark side of ruby
DESCRIPTION
I love Ruby! But as in any relationship, to love means that you (often) have to accept the “dark side” too! Ruby is human in nature and has a lot of gotchas, tricks, wierdness and sometimes scary features that I plan to highlight. This talk aims to provide the “Ah-ha!” moments when working in Ruby. This talk is for beginners and experts alike – in fact, I tag slides to mark their level and beginners can choose to tune out of the heavy stuff!TRANSCRIPT
http://www.flickr.com/photos/sashapo/2722924752/sizes/l/
The Dark Side of Ruby
http://www.flickr.com/photos/sashapo/2722924752/sizes/l/
The Dark Side of Ruby
@gautamrege!@joshsoftware since 2007
What’s the talk about?
• Nothing scary
• Weirdness and Gotcha’s
Ah-ha! Moments
Slides are Tagged
Beginner Expert
(In)Famous Infinityhttp://www.flickr.com/photos/emdot/482622478/sizes/l/
(In)famous Infinity$ irb> 1/0 => ZeroDivisionError: divided by 0
$ irb> 1.0/0 => Infinity
$ irb> Infinity => NameError: uninitialized constant Infinity
Base Jumping
http://www.flickr.com/photos/shahdi/8035647153/sizes/l/
Base Conversions$ irb> 12345.to_s(8) => "30071" # => Octal
$ irb> 12345.to_s(36) => "9ix" # That is an actual number
$ irb> 1234.to_s(64) => ArgumentError: invalid radix 64
The Star - *
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"
Calling out to Stabbyblk = ->(f, *m, sl, l) do puts sl end
blk.call(1, 2, 3, 4, 5, 6) => 5
blk.(1, 2, 3, 4, 5, 6) => 5
call is implied for a stabby proc or a Proc
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?irb> 1 == 1.0 => true # generic equality irb> 1 === 1.0 => true # case equality irb> 1.eql? 1.0 => false # equality by valueirb> 1.equal? 1.0 => false # object identity irb> 'a'.equal? 'a' => false # gotcha!
Proc#curry
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…
Protected from Private
Private methodsclass Base private def foo puts "inside foo" end end class Child < Base def bar foo 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 !prime = Autobot.new("Optimus Prime") megatron = Autobot.new('Megatron') !prime.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
Cherry pick from Modules
module Megatron! def power! p "Megatron's super strength"! end!!
def evil! p 'Evil genius'! end!end
Cherry pick from Modulesclass 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