From X To Ruby

My morning training session at LSRC 2013

Transcript

1. From X To Ruby Anthony Lewis Thursday, July 18, 13
2. About Me • Senior Engineer at Mass Relevance • @anthonylewis • me@anthonylewis.com • http://anthonylewis.com Thursday, July 18, 13
3. Session Overview • Installation • Tools • Syntax • Enumerable • Classes & Modules Thursday, July 18, 13
4. Installation Thursday, July 18, 13
5. Windows • Planning to use Rails? • Use Rails Installer • http://railsinstaller.org • Use Ruby Installer • http://rubyinstaller.org Thursday, July 18, 13
6. Mac OS X • Planning to use Rails? • Use Rails Installer • http://railsinstaller.org • Use Homebrew? • brew install ruby • Try RVM Thursday, July 18, 13
7. Linux • Check your package system • Does it have Ruby 1.9 or later? • Enjoy building from source? • Try RVM Thursday, July 18, 13
8. Ruby Version Manager • For Mac OS X and Linux • Install multiple versions of Ruby • Builds from source • Dev Tools Required • http://rvm.io Thursday, July 18, 13
9. Tools Thursday, July 18, 13
10. Ruby • A dynamic, open source programming language with a focus on simplicity and productivity. It has an elegant syntax that is natural to read and easy to write. • Created by Yukihiro “Matz” Matsumoto • http://www.ruby-lang.org/en Thursday, July 18, 13
11. MINASWAN Matz is nice and so we are nice. Thursday, July 18, 13
12. Gem • RubyGems is the ruby packaging system. It provides a standard format for distributing Ruby programs and libraries, and an easy to use tool for managing the installation of gem packages. • https://rubygems.org Thursday, July 18, 13
13. Bundler • Bundler manages an application's dependencies through its entire life across many machines systematically and repeatably. • http://gembundler.com Thursday, July 18, 13
14. Text Editors • The Classics: Emacs, Vim • Cross Platform: Sublime Text 2 • http://www.sublimetext.com Thursday, July 18, 13
15. Syntax Thursday, July 18, 13
16. Interactive Ruby • Open a Command Prompt or Terminal • Type “irb” and press Enter Thursday, July 18, 13
17. Statements • Separated by line breaks • Use semicolons to include more than one statement on a line • An operator, comma, or dot followed by a line break continues the current statement • Strings can contain line breaks Thursday, July 18, 13
18. Numbers & Math irb> 1 + 2 => 3 irb> 2 * 3 => 6 irb> 6 / 3 => 2 Thursday, July 18, 13
19. Floating Point Math irb> 6 / 3 => 2 irb> 7 / 3 => 2 irb> 7.0 / 3 => 2.33333333333333 Thursday, July 18, 13
20. Strings irb> "Hello" => "Hello" irb> "Hi" + "There" => "HiThere" irb> "Hi" * 3 => "HiHiHi" Thursday, July 18, 13
21. String Interpolation irb> name = "Tony" => "Tony" irb> "Hi #{name}" => "Hi Tony" Thursday, July 18, 13
22. Symbols • Symbols are used as identifiers in Ruby • They are like an immutable string • Use a single memory address irb> :hello => :hello Thursday, July 18, 13
23. Symbols irb> "hello".object_id => 70232873999180 irb> "hello".object_id => 70232873993500 irb> :hello.object_id => 515368 Thursday, July 18, 13
24. Strings vs Symbols • Jim Weirich says... • If the contents of the object are important, use a String. • If the identity of the object is important, use a Symbol. Thursday, July 18, 13
25. Constants • Name starts with an upper case • Typically written in ALL CAPS irb> PI = 3.14 => 3.14 irb> 2 * PI => 6.28 Thursday, July 18, 13
26. Arrays • A list of objects • Enclosed in square brackets irb> list = [1, 2, 3] => [1, 2, 3] irb> list[1] => 2 Thursday, July 18, 13
27. Hashes • A set of key value pairs • Enclosed in curly braces irb> person = {:name => "Tony"} => {:name=>"Tony"} irb> person[:name] => "Tony" Thursday, July 18, 13
28. Ruby 1.9+ Syntax • Drop the hash rocket • Move the colon to the end of the symbol irb> person = {name: "Tony"} => {:name=>"Tony"} irb> person[:name] => "Tony" Thursday, July 18, 13
29. • if executes code if the condition is true Conditionals age = 21 if age < 13 puts "Child" end Thursday, July 18, 13
30. • Use elsif and else to add more conditions Conditionals if age < 13 puts "Child" elsif age < 18 puts "Teenager" else puts "Adult" end Thursday, July 18, 13
31. • If not name empty, print name Conditionals name = "Tony" if !name.empty? puts name end Thursday, July 18, 13
32. • Unless name empty, print name Conditionals name = "Tony" unless name.empty? puts name end Thursday, July 18, 13
33. • Print name, unless name empty Conditionals name = "Tony" puts name unless name.empty? Thursday, July 18, 13
34. Boolean Logic • Any expression can be treated as a boolean • false and nil are considered falsey • All other values are truthy • Use the empty? method to see if a string or collection is empty Thursday, July 18, 13
35. Iteration • In addition to the standard for and while loops in other languages list = [1, 2, 3, 4] list.each do |number| puts number end Thursday, July 18, 13
36. Blocks • Code passed to and executed by a method • A block forms a closure • Local variables are available inside • Surrounded by do ... end or {} • Arguments, if any, go between || Thursday, July 18, 13
37. Blocks list = [1, 2, 3, 4] x = 2 list.each do |number| puts x * number end list.each { |n| puts x * n } Thursday, July 18, 13
38. Blocks • Not just for loops • Pass a block to File.open and it will close the file, even on exceptions File.open("test.txt") do |f| puts f.readlines end Thursday, July 18, 13
39. Methods • A reusable piece of code with a name def greet(name = "World") puts "Hello, #{name}" end irb> greet "Hello, World" => nil Thursday, July 18, 13
40. Enumerable Thursday, July 18, 13
41. Enumerable • Module commonly included in collections • Adds traversal and other methods • all?, any?, collect, count (map), detect (find), first, include?, inject (reduce), max, min, reject, select, sort, take Thursday, July 18, 13
42. all? • Returns true if the given block never returns false or nil irb> list = [1, 2, 3, 4] irb> list.all? { |n| n.even? } => false Thursday, July 18, 13
43. any? • Returns true if the given block ever returns a value other than false or nil irb> list = [1, 2, 3, 4] irb> list.any? { |n| n.even? } => true Thursday, July 18, 13
44. collect (map) • Returns a new array with the result of running the block on each element irb> list = [1, 2, 3, 4] irb> list.map { |n| n * n } => [1, 4, 9, 16] Thursday, July 18, 13
45. detect (find) • Returns the first element where the block is not false irb> list = [1, 2, 3, 4] irb> list.find { |n| n % 2 == 0 } => 2 Thursday, July 18, 13
46. first • Returns the first element of the collection irb> list = [1, 2, 3, 4] irb> list.first => 1 Thursday, July 18, 13
47. include? • Returns true if the collection includes the given object irb> list = [1, 2, 3, 4] irb> list.include? 3 => true Thursday, July 18, 13
48. inject (reduce) • Combine all elements into a single object using the given starting value and block irb> list = [1, 2, 3, 4] irb> list.reduce(0) do |memo, n| irb> memo + n irb> end => 10 Thursday, July 18, 13
49. max, min • Returns the element with the maximum or minimum value respectively irb> list = [1, 2, 3, 4] irb> list.max => 4 Thursday, July 18, 13
50. reject • Returns an array of elements where the block returns false irb> list = [1, 2, 3, 4] irb> list.reject { |n| n.even? } => [1, 3] Thursday, July 18, 13
51. select • Returns an array of elements where the block returns true irb> list = [1, 2, 3, 4] irb> list.select { |n| n.even? } => [2, 4] Thursday, July 18, 13
52. sort • Returns a sorted copy of the collection, using an optional block irb> list = [1, 2, 3, 4] irb> list.sort { |a,b| b <=> a } => [4, 3, 2, 1] Thursday, July 18, 13
53. take • Returns the requested number of elements from the collection irb> list = [1, 2, 3, 4] irb> list.take 2 => [1, 2] Thursday, July 18, 13
54. Method Chaining • Combine several methods irb> list.map { |n| n ** 3 }. select { |n| n.even? }.first => 8 Thursday, July 18, 13
55. Dangerous Methods • Modify the collection in place • Method names end with an exclamation irb> list = [1, 2, 3, 4] irb> list.select! { |n| n.even? } => [2, 4] Thursday, July 18, 13
56. Classes & Modules Thursday, July 18, 13
57. Classes • A collection of data and methods class Person def initialize(name) @name = name end def greet puts "Hi, I'm #{@name}" end end Thursday, July 18, 13
58. Classes • Instantiating and using irb> guy = Person.new("Tony") => irb> guy.greet => "Hi, I'm Tony" Thursday, July 18, 13
59. Instance Variable • A variable that belongs to a specific instance of the class • Protected inside the class • Starts with @ • For example, @name in the Person class Thursday, July 18, 13
60. Instance Variable • Use attr_accessor to make an instance variable available outside the class irb> class Person irb> attr_accessor :name irb> end irb> guy.name => "Tony" Thursday, July 18, 13
61. Instance Method • Methods that are called on a specific instance of the class • For example, guy.greet Thursday, July 18, 13
62. Class Variable • A variable that is shared among all instances of the class, and the class itself • Protected inside the class • Starts with @@ Thursday, July 18, 13
63. Class Method • A method that is called on the class itself • For example, Person.new • Many examples in ActiveRecord • Post.all • Comment.where(post_id: 2) Thursday, July 18, 13
64. Access Modifiers • private - available to instances of the class • protected - available to instances of the class and subclasses • public - available to everyone Thursday, July 18, 13
65. Inheritance • Single inheritance only • Use modules / mixins to model multiple inheritance class Student < Person # ... end Thursday, July 18, 13
66. Modules • Model qualities or abilities of things • Cannot be instantiated • Class names are typically nouns • Module names are typically adjectives Thursday, July 18, 13
67. Modules module Distractible def distract puts "Oh, kittens" end end class Student < Person include Distractible end Thursday, July 18, 13
68. Modules irb> bob = Student.new("Bob") => irb> bob.greet => "Hi, I’m Bob" irb> bob.distract => "Oh, kittens" Thursday, July 18, 13
69. Resources Thursday, July 18, 13
70. Learn More Ruby • Programming Ruby 1.9 & 2.0 • The PickAxe Book • by Dave Thomas, with Chad Fowler and Andy Hunt Thursday, July 18, 13
71. Learn Onscreen • Try Ruby • http://tryruby.org • Ruby Koans • http://rubykoans.com • Ruby has damaged your karma. Thursday, July 18, 13
72. Thursday, July 18, 13