9 Things Every Ruby Newbie Should Know

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9 @bkeepers things every Ruby Newbie should know

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Jim Weirich 10 Things Every Java Programmer Should Know About Ruby http://onestepback.org/articles/10things/

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learn the Ruby way

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linguistic relativity the structure of a language aﬀects the ways in which its speakers are able to conceptualize their world

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“A language that doesn’t affect the way you think about programming is not worth knowing.” Alan Perlis

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don’t just write in Ruby Java

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don’t just write in Ruby Perl

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don’t just write in Ruby PHP

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don’t just write in Ruby C#

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Learn the Ruby Way

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follow the conventions

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ClassName

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@instance_variable

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$global_variable

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SomeConstant ANOTHER_CONSTANT

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method_name variable_name

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method?

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dangerous_method!

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ClassName file_name.rb

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Class#method

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2 space indent

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some are enforced

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some are community standards

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all values are objects

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anything that can be bound to a variable

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no primitives 0.zero? # => true 1.zero? # => false -1.abs # => 1 10.class # => Fixnum (10**100).class # => Bignum true.class # => TrueClass

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nil is an object a = nil a.nil? # => true a.methods # => list of methods a.class # => NilClass a.abs # => NoMethodError

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classes are objects a = Array.new

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almost everything is a message

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computation… 1. assignment (binding objects to names) 2. primitive control structures (if, else, while) and operators (defined?) 3. sending messages to objects

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messages are not just function calls

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function calls use internal lookup tables

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messages delegate to the object

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'hello'.count('l')

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'hello'.send(:count, 'l')

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operators are syntactic sugar 1 + 2 1.+(2) 1.send(:+, 2)

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array[0] array.send(:[], 0)

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method_missing class VCR def initialize @messages = [] end def method_missing(method, *args, &block) @messages << [method, args, block] end def play_back_to(obj) @messages.each do |method, args, block| obj.send(method, *args, &block) end end end

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method_missing require 'vcr' vcr = VCR.new vcr.sub!(/Hello/) { "Goodbye" } vcr.upcase! vcr[8,5] = "Universe" vcr << "!" string = "Hello World" puts string vcr.play_back_to(string) puts string Outputs: Hello World GOODBYE Universe!

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truthiness

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nil and false are false

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everything else is true

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puts "including zero" if 0

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Strong dynamic typing

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weak

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strong 5 + "5" TypeError: String can't be coerced into Fixnum

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5 + "5".to_i

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strong dynamic typing

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static String str = new String("compile"); str = 5; incompatible types found : int required: java.lang.String

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dynamic a = "runtime" a = [ ]

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strong dynamic typing

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duck typing class Duck def talk "quack!" end end class Goose def talk "honk!" end end birds = [Duck.new, Goose.new] birds.each {|b| b.talk }

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modules

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namespace module GitHub class User end end user = GitHub::User.new

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mix-in module Logging def logger @logger ||= Logger.new(opts) end end class Person include Logging def relocate logger.debug "Relocating person..." # do relocation stuff end end

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Comparable class SizeMatters < Struct.new(:str) include Comparable def <=>(other) str.size <=> other.str.size end end s1 = SizeMatters.new("Z") s2 = SizeMatters.new("YY") s3 = SizeMatters.new("XXX") s1 < s2 #=> true s3.between?(s1, s2) #=> false s2.between?(s1, s3) #=> true [ s3, s1, s2 ].sort #=> [Z, YY, XXX]

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embrace closures

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Iteration [1,2,3].each { |item| puts item }

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Resource Management file_contents = open(file_name) { |f| f.read }

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Callbacks widget.on_button_press { puts "Got Button Press" }

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Ruby is loose

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optional parenthesis puts 'Hello World' puts('Hello World') 'Hello World'.count 'l' puts 'Hello World'.count 'l' puts 'Hello World'.count('l')

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optional semicolons puts 'Hello World'; don’t use them

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“constants” Timeout = 30 Timeout = 50 warning: already initialized constant Timeout puts Timeout 50

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open classes class Integer def even? (self % 2) == 0 end end (1..10).select { |n| n.even? } # => [2, 4, 6, 8, 10]

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Summary 1. learn the Ruby way 2. follow the conventions 3. all values are objects 4. everything is a message 5. truthiness 6. strong dynamic typing 7. modules 8. embrace enclosures 9. Ruby is loose

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Thanks! @bkeepers

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License This presentation is based on “10 Things Every Java Programmer Should Know About Ruby” by Jim Weirich. http://onestepback.org/articles/10things/license.html This presentation is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License. http://creativecommons.org/licenses/by-nc/3.0/