Ruby For Beginning Rails Programmers

For Columbia's Ruby on Rails class. November 2012.

Transcript

1. Ruby Ruby Ruby
2. Goals: 1. why Ruby is cool (or why to stop writing java) 2. how Ruby works 3. how Ruby solves complex problems 4. a taste of what Ruby can do
3. there are some things that you should know
4. use the “idioms”
5. Social Mores.
6. use each, always not for!
7. # yup a_method that: ‘takes’, a_hash: ‘argument’ a_method :that => ‘takes’, :a_hash => ‘argument’ # WASTE OF PRECIOUS BYTES!!! a_method({:that => ‘takes’, :a_hash => ‘argument’}) a_method {:that => ‘takes’, :a_hash => ‘argument’}
8. # throws an error, works in place object.dangerous_method! # returns a boolean object.awesome?
9. two spaces, no tabs
10. # on your machine def do_something @var += 1 @students.each do { |s| s.teach! s.fail! } end
11. # on github, your friend’s machine def do_something @var += 1 @students.each do { |s| s.teach! s.fail! } end
12. everything is an object
13. “hey there” 5 [1, 2, 3]
14. nil # NilClass false # FalseClass String # Class
15. “hey there”.send :upcase #=> “HEY THERE” 5.send :+ , 1 #=> 6 [1, 2, 3].send :length #=> 3
16. “hey there”.upcase #=> “HEY THERE” 5.+ 1 #=> 6 [1, 2, 3].length #=> 3
17. methods come from somewhere
18. “blahhh”.class #=> String
19. String.ancestors #=> [Object, Kernel, BasicObject]
20. def say something puts something end #=> nil
21. def say something Kernel.puts something end #=> nil
22. case study:
23. Trainer = Class.new
24. Trainer = Class.new do def name “Unknown” end end ash = Trainer.new ash.name #=> “Unknown”
25. Trainer = Class.new do def name @name || “Unknown” end def name= something @name = something end end ash = Trainer.new ash.name = “Ash” ash.name #=> “Ash”
26. Trainer = Class.new do def initialize name = nil @name = name end def name @name || “Unknown” end def name= something @name = something end end
27. Trainer = Class.new do def initialize name = “Unknown” @name = name end def name @name end def name= something @name = something end end
28. ash = Trainer.new “Ash Ketchum”
29. class Trainer attr_reader :name # def name attr_writer :name # def name= def initialize name = “Unknown” @name = name end end
30. class Trainer # def name, def name= attr_accessor :name def initialize name = “Unknown” @name = name end end
31. Trainer = Struct.new :name
32. ash = Trainer.new “Ash Ketchum”
33. ash = Trainer.new “Ash Ketchum” ash.name #=> “Ash Ketchum” ash.name = “Ash”
34. Lessons:
35. ONE code that doesn’t exist has no bugs
36. TWO classes are only a little bit special
37. # new instance of a blank class, Class Trainer = Class.new # syntactic sugar so that it looks familiar class Trainer end # new instance of a class with an # initializer, getter, and setter Trainer = Struct.new :name
38. Class is a class that happens to be named “Class”
39. the Trainer class is an instance of the class Class
40. class Trainer < Class.new end # works class Student < User.new end # TypeError: superclass must be a Class (User given)
41. why does this matter?
42. you can do anything everything is open* & *almost
43. Struct i make classes
44. [:a, :b, :b].each do |name| define_method name do “I’m #{name}” end end
45. class RudeClass def method_missing method_name, *args, &block formatted = method_name.to_s.gsub(‘_’, ‘ ‘) “No, you #{formatted}” end end r = RudeClass.new r.dance! #=> “No, you dance!” r.go_away! #=> “No, you go away!”
46. a = “hey” class String def secret_password “The password is 2ryp4py3g” end end a.secret_password #=> “The password is 2ryp4py3g”
47. class Government # Boring stuff omitted... private def launch_nuke! # top secret contents omitted... “Mission Success!” end end g = Government.new g.launch_nuke! #=> NoMethodError g.send :launch_nuke! #=> ‘Mission Success!’
48. def benchmark method, num = 10000, *args, &block start = Time.now num.times { send method } (Time.now - start) / num end benchmark :size #=> 1.46441e-07
49. Constant = 10 Constant = 11 warning: already initiated constant Constant Constant #=>11 def Constant.constant? false end Constant.constant? #=> false “constants”
50. with Ruby, you can solve complex problems very simply