You and Your Type[s] Aren't Welcome Here

Thinking in a type-driven fashion doesn't require throwing Ruby away. Here are some examples of how types can make our Ruby programs better, while still looking and feeling like Ruby.

Transcript

1. Self-Evident Truths
2. PHP is Better than ruby
3. Sydney is Better than Melbourne
4. Tea is better than coffee
5. JSON is better than XML
6. VIM is better than emacs
8. You and Your Type[s] Aren't Welcome Here
9. Andy Nicholson Cogent Co @andrewdotnich /dev/null
12. public static void main(String[] args) { //sigh }
13. I made up the term ‘object- oriented,’ and I can tell you I didn't have C++ in mind. — Alan Kay, OOPSLA ’97
17. method_missing
18. ==:blub
19. Objects are a poor person’s closures.
20. None of that
24. Types Are Metadata
25. unsigned long variable; short byte_number; /* C */
26. double floating_point; decimal bcd_encoded; bool flag; // C ++
27. let mut x = 5; // Rust final double Tau = 6.2831852; // Java VERSION = '5.6.28'; // PHP
28. var value : integer; pointer_to_integer: ^integer; begin value := 42; pointer_to_integer := @value; end. {* Pascal *}
29. What about Ruby?
30. public class Pet { private String name; private Person owner; public Pet(String name, Person owner) { this.name = name; this.owner = owner; } public String getName() { return name; } public void setName(String name) { this.name = name; } public Person getOwner() { return owner; } public void setOwner(Person owner) { this.owner = owner; } }
31. class Pet attr_accessor :name, :owner def initialize(name, owner) @name = name @owner = owner end end
32. Pet = Struct.new(:name, :owner) dog = Pet.new 'fido', :me # but please don't do this!
33. TypeError: no implicit conversion of String into Integer from reporting.rb:10 in `[]’
34. Types Are Metadata
35. Ruby has types
37. Everything is an object
38. foo.bar expect(foo).to respond_to(:bar)
40. If a method responds to the methods we expect it to, it’s probably* the right type.
42. There are trade-offs
43. fail 'sometimes'
44. def print_items(collection) collection.each do |item| puts " #{item[:code].upcase}: #{item[:price]}" end end def process_report(data) # ... # ... print_items(data) end # What happens here? process_report([{}])
45. /tmp/reporting.rb:3:in `block in print_items': undefined method `upcase' for nil:NilClass (NoMethodError)
46. def print_items(collection) collection.each do |item| puts " #{item.fetch(:code).upcase}: #{item[:price]}" end end
47. /tmp/reporting.rb:3:in `fetch': key not found: :code (KeyError)
48. process_report( [ [] ] )
49. /tmp/reporting.rb:3:in `fetch': no implicit conversion of Symbol into Integer (TypeError)
51. Array Hash
52. def takes_a_hash(hash) hash[:some_key] end takes_a_hash [1,2,3]
53. def print_items(collection) collection.each do |items| items = Hash(items) puts " #{collection.fetch(:code).upcase}: #{collection[:price]}" end end
54. process_report([ [] ]) # /tmp/reporting.rb:4:in `fetch': key not found: :code (KeyError) process_report([ {} ]) # /tmp/reporting.rb:4:in `fetch': key not found: :code (KeyError) process_report( [ [1] ]) # /tmp/reporting.rb:3:in `Hash': can't convert Array into Hash (TypeError)
55. class Plant def initialize(code:, price:) # … end attr_reader :code, :price def to_hash { code: code, price: price } end end process_report([Plant.new(code: "NOT_A_POT_JOKE", price: 419) ]) # => outputs "NOT_A_POT_JOKE: 419"
56. Curious? • Confident Ruby, by Avdi Grimm ( http://confidentruby.com/ ) • contracts.ruby ( http://github.com/egonSchiele/contracts.ruby ) • dry-types ( http://github.com/dry-rb/ )
58. result = operation_that_may_fail_1(data) if result result = operation_that_may_fail_2(result) if result result = operation_that_may_fail_3(result) end end
59. begin result = operation_that_may_fail_1(data) result = operation_that_may_fail_2(result) result = operation_that_may_fail_3(result) rescue Failure1 => f # … rescue Failure2 => f2 # … rescue Failure3 => f3 # … end
60. result = nil begin result = operation_that_may_fail_1(data) rescue Failure1 => f return "Unable to perform step 1: #{e.message}" end begin result = operation_that_may_fail_2(result) rescue Failure1 => f2 return "Step 2 failed " end begin result = operation_that_may_fail_3(result) rescue Failure1 => f3 return "" end
61. Yuk
62. r = Try() { operation_that_may_fail1(data) } .bind { |result| operation_that_may_fail2(result) } .bind { |result| operation_that_may_fail3(result) } if r.success? r.value else raise res.exception # or log, or whatever end
63. ¯\_(ϑ)_/¯
64. So What?
65. import this
66. Ruby is 和
67. @andrewdotnich @cogent_co SDG