Is Your Code Too SOLID?

This version does NOT include a talk transcript; version with transcript is here:
https://speakerdeck.com/sarahmei/is-your-code-too-solid-with-transcript

SOLID is a collection of five common object-oriented development principles collected into one handy acronym. Smart people recommend learning about it, and even the name sounds fantastic — who doesn’t want to write “solid” code? Clearly, you should strive to follow all five principles, all the time, in all of your code. Right? Well. Good object-oriented design is indeed helpful, but SOLID as a set of guiding principles really isn’t. Let’s break SOLID down and reveal the limitations of our current approach, and try to understand just how SOLID our code needs to be.

Transcript

1. S A R A H M E I W D C N Z 2 0 1 5 I S Y O U R C O D E TO O S O L I D ? https://www.flickr.com/photos/pie4dan/4567311801
2. DevMynd S A R A H M E I C H I E F C O N S U LTA N T D E V M Y N D U N I T E D S TAT E S C H I E F O F BA L D E A G L E S A N D F R E E D O M http://world-map1.org/map1520769_0_0.htm http://www.coolholidaygraphics.com/flagday/glittergraphics/flagdayglitter2.gif https://www.devmynd.com/images/team/sarah-mei-cutout.png
3. DevMynd
4. C O D E BA S E S I WO R K O N N O R M A L C O D E BA S E S https://www.flickr.com/photos/pmarkham/5361277692
5. AT F I R S T https://www.flickr.com/photos/jakerust/16661140289/
6. https://www.flickr.com/photos/123638374@N08/14184697490
7. https://www.flickr.com/photos/123638374@N08/14184697490
8. DevMynd https://twitter.com/tenderlove/status/573907559871971328
9. DevMynd https://twitter.com/tenderlove/status/573907559871971328
10. DevMynd S A N D I M E T Z E X P E RT AT E V E RY T H I N G S E R I O U S LY, G E T I T A M A Z I N G B O O K http://www.sandimetz.com/ http://www.poodr.com/
11. DevMynd S A N D I M E T Z E X P E RT AT E V E RY T H I N G S E R I O U S LY, G E T I T A M A Z I N G B O O K http://www.sandimetz.com/ http://www.poodr.com/
12. D E S I G N D E C I D I N G H OW TO A R R A N G E C O D E https://www.flickr.com/photos/matley0/3616669592
13. D E S I G N D E C I D I N G H OW TO A R R A N G E C O D E https://www.flickr.com/photos/matley0/3616669592
14. O B J E C T- O R I E N T E D D E S I G N G R O U P I N G R E L AT E D F U N C T I O N A L I T Y I N O B J E C T S https://www.flickr.com/photos/mwanasimba/2901201955/
15. DevMynd A L A N G UA G E F E AT U R E A WAY O F T H I N K I N G O B J E C T- O R I E N T E D D E S I G N I S https://www.flickr.com/photos/56627607@N05/15635620289/
16. DevMynd A L A N G UA G E F E AT U R E A WAY O F T H I N K I N G O B J E C T- O R I E N T E D D E S I G N I S A D E S T I N AT I O N A M E A N S TO A N E N D https://www.flickr.com/photos/56627607@N05/15635620289/
17. https://www.flickr.com/photos/redvers/532076662/
18. https://www.flickr.com/photos/redvers/532076662/
19. H I G H L OW H I G H L OW C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E
20. H I G H L OW H I G H L OW C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E
21. H I G H L OW H I G H L OW Procedures C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E
22. H I G H L OW H I G H L OW Procedures C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E
23. CalendarParamMgr GetCalendarIndex CalendarRouteResolver CalendarRouteResolverFactory RouteResolver RouteReceiver
24. H I G H L OW H I G H L OW Procedures Set of Small Objects C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E
25. H I G H L OW H I G H L OW Procedures ⚠⚡ Set of Small Objects C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E
26. H I G H L OW H I G H L OW Procedures Set of Small Objects C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E Really big objects
27. H I G H L OW H I G H L OW Procedures Set of Small Objects C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E Really big objects The wrong set of small objects
28. H I G H L OW H I G H Procedures Set of Small Objects L OW C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E Really big objects The wrong set of small objects
29. H I G H L OW H I G H Procedures Set of Small Objects L OW C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E Really big objects The wrong set of small objects
30. PAT T E R N S https://www.flickr.com/photos/dakluza/6665460621
31. O B S E R V E R N E W E M A I L User
32. O B S E R V E R User UserObserver
33. O B S E R V E R User UserObserver ! E M A I L N E W
34. H I G H L OW H I G H L OW E A S I E R TO C H A N G E H A R D E R TO U N D E R S TA N D C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E
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38. N A M E S U M M A RY U T I L I T Y S O L I D
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41. N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O L I D
42. O P E N / C L O S E D P R I N C I P L E S O L I D https://www.flickr.com/photos/28481088@N00/4063800774/
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44. L I S KOV S U B S T I T U T I O N P R I N C I P L E S O L I D https://www.flickr.com/photos/vpickering/14416940341/
45. DevMynd Let Φ(x) be a property provable about objects x of type T. Then Φ(y) should be true for objects y of type S where S is a subtype of T.
46. L I S KOV S U B S T I T U T I O N P R I N C I P L E S O L I D https://www.flickr.com/photos/vpickering/14416940341/
47. I T ’ S N E V E R TO O L AT E TO https://www.flickr.com/photos/wcouch/8578612563/
48. N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O O P E N / C L O S E D D O N ’ T E D I T C O D E ; A D D N E W C O D E L O W L L I S K O V S U B S T I T U T I O N I N H E R I TA N C E . I T ’ S A T H I N G . L O W I D
49. I N T E R FA C E S E G R E G AT I O N P R I N C I P L E S O L I D https://www.flickr.com/photos/66126733@N04/8477516123/i
50. W H Y S E G R E G AT E I N T E R FA C E S ? Musician AlbumCreator recordSong editSong mixSong sellMerch playSetList Gig
51. W H Y S E G R E G AT E I N T E R FA C E S ? Musician AlbumCreator recordSong editSong mixSong sellMerch playSetList Gig driveVan
52. W H Y S E G R E G AT E I N T E R FA C E S ? StudioActions AlbumCreator recordSong editSong mixSong sellMerch playSetList Gig driveVan VenueActions
53. N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O O P E N / C L O S E D D O N ’ T E D I T C O D E ; A D D N E W C O D E L O W L L I S K O V S U B S T I T U T I O N I N H E R I TA N C E . I T ’ S A T H I N G . L O W I I N T E R FA C E S E G R E G AT I O N M A K E T H E A P I S M A L L H I G H D
54. D E P E N D E N C Y I N V E R S I O N P R I N C I P L E S O L I D https://www.flickr.com/photos/hansmaulwurf/13702053625/
55. N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O O P E N / C L O S E D D O N ’ T E D I T C O D E ; A D D N E W C O D E L O W L L I S K O V S U B S T I T U T I O N I N H E R I TA N C E . I T ’ S A T H I N G . L O W I I N T E R FA C E S E G R E G AT I O N M A K E T H E A P I S M A L L H I G H D D E P E N D E N C Y I N V E R S I O N M O V E C H O I C E S T O E D G E S O F S Y S T E M H I G H
56. N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O O P E N / C L O S E D D O N ’ T E D I T C O D E ; A D D N E W C O D E L O W L L I S K O V S U B S T I T U T I O N I N H E R I TA N C E . I T ’ S A T H I N G . L O W I I N T E R FA C E S E G R E G AT I O N M A K E T H E A P I S M A L L H I G H D D E P E N D E N C Y I N V E R S I O N M O V E C H O I C E S T O E D G E S O F S Y S T E M H I G H
57. N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O O P E N / C L O S E D D O N ’ T E D I T C O D E ; A D D N E W C O D E L O W L L I S K O V S U B S T I T U T I O N I N H E R I TA N C E . I T ’ S A T H I N G . L O W I I N T E R FA C E S E G R E G AT I O N M A K E T H E A P I S M A L L H I G H D D E P E N D E N C Y I N V E R S I O N M O V E C H O I C E S T O E D G E S O F S Y S T E M H I G H
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62. G OA L : P R O M O U N TA I N E E R S T R AT E G Y: C L I M B T H I S M T N TA C T I C S : T H E R O U T E U P \ O / https://www.flickr.com/photos/frenchy/222016256/
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64. G OA L : C H A N G E A B L E S O F T WA R E S T R AT E G Y: TA C T I C S : O O D E S I G N S O L I D https://www.flickr.com/photos/sunfox/5084875405/
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66. N A M E S U M M A RY U T I L I T Y S S I N G L E R E S P O N S I B I L I T Y O N E R E S P O N S I B I L I T Y P E R C L A S S M E D O O P E N / C L O S E D D O N ’ T E D I T C O D E ; A D D N E W C O D E L O W L L I S K O V S U B S T I T U T I O N I N H E R I TA N C E . I T ’ S A T H I N G . L O W I I N T E R FA C E S E G R E G AT I O N M A K E T H E A P I S M A L L H I G H D D E P E N D E N C Y I N V E R S I O N M O V E C H O I C E S T O E D G E S O F S Y S T E M H I G H
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70. https://www.flickr.com/photos/jonathancohen/15420956905
71. H I G H L OW H I G H L OW The wrong set of small objects ❗ C O S T O F U N D E R S TA N D I N G C O S T O F C H A N G E
72. DevMynd T H E O N LY WAY TO M A K E A S TO P - T H E - WO R L D R E FA C TO R I N G WO R K I S TO N OT D O I T . http://www.imdb.com/title/tt0086567/
73. https://www.flickr.com/photos/frenchy/222016256/
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75. DevMynd post.comments.first.author.email NOPE
76. DevMynd https://www.flickr.com/photos/83794824@N07/8059223873/
77. S TA B L E
78. S TA B L E
79. S TA B L E S M E L L Y O U R C O D E https://www.flickr.com/photos/pedrosimoes7/169983321/
80. T I N Y P R O B L E M S F I R S T S TA B L E https://www.flickr.com/photos/ian-arlett/13706787684/
81. S TA B L E https://www.flickr.com/photos/ian-arlett/13706787684/ T I N Y P R O B L E M S F I R S T
82. A U G M E N T T E S T S S TA B L E https://www.flickr.com/photos/horiavarlan/4273968004/
83. https://www.flickr.com/photos/horiavarlan/4273968004/ S TA B L E A U G M E N T T E S T S
84. S TA B L E BA C K U P https://www.flickr.com/photos/mjonasson/19228720295/
85. S TA B L E L E AV E I T B E T T E R T H A N Y O U F O U N D I T https://www.flickr.com/photos/spierisf/6989462184/
86. https://www.flickr.com/photos/spierisf/6989462184/ S TA B L E L E AV E I T B E T T E R T H A N Y O U F O U N D I T
87. https://www.flickr.com/photos/spierisf/6989462184/ S TA B L E L E AV E I T B E T T E R T H A N Y O U F O U N D I T
88. E X P E C T G O O D R E A S O N S S TA B L E https://www.flickr.com/photos/an_untrained_eye/5012331537
89. https://www.flickr.com/photos/an_untrained_eye/5012331537 S TA B L E E X P E C T G O O D R E A S O N S
90. S S M E L L Y O U R C O D E T T I N Y P R O B L E M S F I R S T A A U G M E N T T E S T S B B A C K U P L L E AV E I T B E T T E R E E X P E C T G O O D R E A S O N S
91. S S M E L L Y O U R C O D E T T I N Y P R O B L E M S F I R S T A A U G M E N T T E S T S B B A C K U P L L E AV E I T B E T T E R E E X P E C T G O O D R E A S O N S
92. DevMynd https://twitter.com/kentbeck/status/250733358307500032
93. DevMynd https://twitter.com/kentbeck/status/250733358307500032
94. https://www.flickr.com/photos/frenchy/222016256/
95. \ O / https://www.flickr.com/photos/frenchy/222016256/
96. https://www.flickr.com/photos/bevrichardmartin/5985876061/ https://www.flickr.com/photos/discarnate/27211024/ https://www.flickr.com/photos/lynardie/16191183291/
97. DevMynd Sarah Mei sarah@devmynd.com @sarahmei THANK YOU!