Surrender The Illusion of Control

SwanseaCon 2015

Transcript

1. Surrender The Illusion of Control @tooky – SwanseaConf 2015
2. Let It Go @tooky – SwanseaConf 2015
3. Caveat
4. What is good design?
5. Why is good design important?
11. Reduce the Cost of Change
13. XP
14. TDD
15. JUnit
16. 4 Rules of Simple Design
22. Your code is your understanding of the problem you're exploring.
23. So it's only when you have your code in your head that you really understand the problem. 1 Paul Graham
25. Connascence
28. Connascence1 1. The birth of two or more things at the same time. 2. The act of growing together 1 From wiktionary
29. two components are connascent if a change in one would require the other to be modified in order to maintain the overall correctness of the system
30. Static Connascence 1. Connascence of Name 2. Connascence of Type 3. Connascence of Meaning 4. Connascence of Algorithm 5. Connascence of Position
31. Dynamic Connascence 6. Connascence of Execution 7. Connascence of Timing 8. Connascence of Value 9. Connascence of Identity
32. Connascence of Name
33. Connascence of Name class CardTest < Minitest::Test def test_high_card_beats_low_card high_card = Card.new("10", "♥") low_card = Card.new("2", "♣") assert high_card.beats?(low_card) end end class Card < Struct.new(:rank, :suit) def beats?(other_card) true end end
34. Connascence of Type
35. Connascence of Type public class DiamondTest { @Test public void first_row_of_A_diamond() { String diamond = Diamond.upTo("A"); assertThat(diamond, is("A")); } @Test public void first_row_of_B_diamond() { String diamond = Diamond.upTo("B"); assertThat(diamond, is("-A-")); } @Test public void first_row_of_C_diamond() { String diamond = Diamond.upTo("C"); assertThat(diamond, is("--A--")); } }
36. Connascence of Type public class Diamond { public static String upTo(String letter) { if ("C".equals(letter)) { return "--" + "A" + "--"; } if ("B".equals(letter)) { return "-" + "A" + "-"; } return "A"; } }
37. public class DiamondTest { @Test public void first_row_of_A_diamond() { String diamond = Diamond.upTo("A"); assertThat(diamond, is("A")); } // ... } public class Diamond { public static String upTo(String letter) { if ("C".equals(letter)) { return "--" + "A" + "--"; } if ("B".equals(letter)) { return "-" + "A" + "-"; } return "A"; } }
38. Connascence of Type public class DiamondTest { @Test public void first_row_of_A_diamond() { String diamond = Diamond.upTo('A'); assertThat(diamond, is("A")); } @Test public void first_row_of_B_diamond() { String diamond = Diamond.upTo('B'); assertThat(diamond, is("-A-")); } @Test public void first_row_of_C_diamond() { String diamond = Diamond.upTo('C'); assertThat(diamond, is("--A--")); } }
39. Connascence of Type public class Diamond { public static String upTo(char letter) { if ('C'.equals(letter)) { return "--" + "A" + "--"; } if ('B'.equals(letter)) { return "-" + "A" + "-"; } return "A"; } }
40. Connascence of Meaning
41. Connascence of Meaning public class Diamond { public static String upTo(char letter) { if ('C'.equals(letter)) { return "--" + "A" + "--"; } if ('B'.equals(letter)) { return "-" + "A" + "-"; } return "A"; } }
42. Connascence of Name > Connascence of Meaning public class Diamond { public static final char START_LETTER = 'A'; public static String upTo(char letter) { if ('C'.equals(letter)) { return "--" + START_LETTER + "--"; } if ('B'.equals(letter)) { return "-" + START_LETTER + "-"; } return valueof(START_LETTER); } }
43. Connascence of Algorithm
44. Connascence of Algorithm public class Diamond { public static final char START_LETTER = 'A'; public static String upTo(char letter) { if ('C'.equals(letter)) { return "--" + START_LETTER + "--"; } if ('B'.equals(letter)) { return "-" + START_LETTER + "-"; } return valueof(START_LETTER); } }
45. Connascence of Algorithm public class Diamond { public static final char START_LETTER = 'A'; public static String upTo(char letter) { if ('C'.equals(letter)) { return "--" + START_LETTER + "--"; } if ('B'.equals(letter)) { return "-" + START_LETTER + "-"; } return "" + START_LETTER + ""; } }
46. Connascence of Name > Connascence of Algorithm public class Diamond { public static final char START_LETTER = 'A'; public static String upTo(char letter) { return padding(letter) + START_LETTER + padding(letter); } private static string padding(char letter) { int paddingSize = letter - START_LETTER; return StringUtils.repeat("-", paddingSize); } }
47. Connascence of Position
48. Connascence of Position class CardTest < Minitest::Test def test_high_card_beats_low_card high_card = Card.new("10", "♥") low_card = Card.new("2", "♣") assert high_card.beats?(low_card) end end class Card < Struct.new(:rank, :suit) end
49. Connascence of Position class CardTest < Minitest::Test def test_high_card_beats_low_card high_card = Card.new("10", "♥") low_card = Card.new("2", "♣") assert high_card.beats?(low_card) end end class Card < Struct.new(:suit, :rank) end
50. Connascence of Position class CardTest < Minitest::Test def test_high_card_beats_low_card high_card = Card.new("♥", "10") low_card = Card.new("♣", "2") assert high_card.beats?(low_card) end end class Card < Struct.new(:suit, :rank) end
51. Connascence of Name > Position class Card def initialize(rank:, suit:) @rank = rank @suit = suit end # ... end
52. Connascence of Name > Position class CardTest < Minitest::Test def test_high_card_beats_low_card high_card = Card.new(rank: "10", suit: "♥") low_card = Card.new(suit: "♣", rank: "2") assert high_card.beats?(low_card) end end
53. Locality
56. Locality class AvailableJobs def jobs [[customer, description]] end def assign_to(worker) jobs.each do |customer, description| # ... end end end
57. Locality class AvailableJobs def jobs [[description, customer]] end def assign_to(worker) jobs.each do |customer, description| # ... end end end
58. Locality class CompletedJobs def jobs [[customer, description]] end end
59. Locality class InvoiceClerk def generate_job_invoices(jobs) jobs.each do |customer, description| # ... end end end
60. Degree
61. Degree class CompletedJobs def jobs [[customer, reference, description, start_time, finish_time, rate]] end end
62. Degree class InvoiceClerk def generate_job_invoices(jobs) jobs.each do |customer, reference, description, start_time, finish_time, rate| # ... end end end
63. Degree class CompletedJob attr_reader :customer, :reference, :description, :start_time, :finish_time, :rate end
64. Degree class CompletedJobs def jobs [job] end end
65. Degree class InvoiceClerk def generate_job_invoices(jobs) jobs.each do |job| # ... end end end
66. Rules
67. The further apart two components are use weaker forms of connascence
68. When you have a high degree of connascence convert to a weaker form of connascence
69. Good Design?
70. Connascence
71. Red, Green... what now?2 2 http://silkandspinach.net/2015/05/20/red-green-what-now/
72. Principles
73. SOLID
74. DRY
75. Law of Demeter
76. Principles
78. Questions
79. http://tooky.co.uk steve@boxjump.co.uk @tooky
80. Photos good_design_1.jpg: https://www.flickr.com/photos/opalsson/ bad_design.jpg: https://www.reddit.com/r/todayilearned/comments/2dvvja/til_that_in_order_to_preserve_the_states_natural/ greenfield.jpg: https://www.flickr.com/photos/ks_marks/ stuckInTheMud.jpg: https://www.flickr.com/photos/puuikibeach/ unicorn.jpg: https://www.flickr.com/photos/wayfinder/ jimWeirich.jpg: https://www.flickr.com/photos/fraserspeirs/ celebrate.jpg: https://www.flickr.com/photos/clement127/ modular.jpg: https://www.flickr.com/photos/rahul3/ connected.jpg: https://www.flickr.com/photos/bernd_thaller/ reduceCost.jpg: https://www.flickr.com/photos/68751915@N05/ change.jpg: https://www.flickr.com/photos/petereed/