Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Features
Speaker Deck
PRO
Sign in
Sign up for free
Search
Search
Why Every Element of SOLID is Wrong
Search
Daniel Terhorst-North
PRO
January 20, 2017
Technology
130
110k
Why Every Element of SOLID is Wrong
Five minute Ignite-style talk from PubConf London 2016
Daniel Terhorst-North
PRO
January 20, 2017
Tweet
Share
More Decks by Daniel Terhorst-North
See All by Daniel Terhorst-North
The best programmer I know
tastapod
PRO
2
210
How to bake a change
tastapod
PRO
0
460
The Most Dangerous Phrase
tastapod
PRO
7
6.1k
Rethinking Transformation
tastapod
PRO
1
360
CUPID - for joyful coding
tastapod
PRO
4
7.2k
agility at scale - a meeting of mindsets
tastapod
PRO
1
570
SWARMing into action
tastapod
PRO
0
380
Deliberate Advice
tastapod
PRO
3
1.5k
Governing Agile Delivery
tastapod
PRO
14
300
Other Decks in Technology
See All in Technology
転生CISOサバイバル・ガイド / CISO Career Transition Survival Guide
kanny
3
960
自動テストの世界に、この5年間で起きたこと
autifyhq
10
8.4k
AndroidデバイスにFTPサーバを建立する
e10dokup
0
250
株式会社EventHub・エンジニア採用資料
eventhub
0
4.3k
一度 Expo の採用を断念したけど、 再度 Expo の導入を検討している話
ichiki1023
1
160
アジャイル開発とスクラム
araihara
0
170
目の前の仕事と向き合うことで成長できる - 仕事とスキルを広げる / Every little bit counts
soudai
24
7k
現場の種を事業の芽にする - エンジニア主導のイノベーションを事業戦略に装着する方法 -
kzkmaeda
2
2k
『衛星データ利用の方々にとって近いようで触れる機会のなさそうな小話 ~ 衛星搭載ソフトウェアと衛星運用ソフトウェア (実物) を動かしながらわいわいする編 ~』 @日本衛星データコミニティ勉強会
meltingrabbit
0
140
リーダブルテストコード 〜メンテナンスしやすい テストコードを作成する方法を考える〜 #DevSumi #DevSumiB / Readable test code
nihonbuson
11
7.1k
Platform Engineeringは自由のめまい
nwiizo
4
2k
「海外登壇」という 選択肢を与えるために 〜Gophers EX
logica0419
0
700
Featured
See All Featured
[RailsConf 2023] Rails as a piece of cake
palkan
53
5.2k
Typedesign – Prime Four
hannesfritz
40
2.5k
Automating Front-end Workflow
addyosmani
1368
200k
Imperfection Machines: The Place of Print at Facebook
scottboms
267
13k
Reflections from 52 weeks, 52 projects
jeffersonlam
348
20k
The Art of Programming - Codeland 2020
erikaheidi
53
13k
Building Your Own Lightsaber
phodgson
104
6.2k
Why Our Code Smells
bkeepers
PRO
336
57k
Bootstrapping a Software Product
garrettdimon
PRO
306
110k
Rails Girls Zürich Keynote
gr2m
94
13k
ピンチをチャンスに:未来をつくるプロダクトロードマップ #pmconf2020
aki_iinuma
114
50k
[Rails World 2023 - Day 1 Closing Keynote] - The Magic of Rails
eileencodes
33
2.1k
Transcript
Why Every Single Element of SOLID is Wrong! Dan North
@tastapod
Single Responsibility Open/Closed Liskov Substitution Interface Segregation Dependency Inversion
Single Responsibility Principle “one reason to change” “only do one
thing”
Single Responsibility Principle What is a single responsibility anyway? ETL:
three responsibilities or one? How can you predict what is going to change? Pointlessly Vague Principle
Single Responsibility Principle Simple code is easy to reason about
Can easily do several related things Refactor until it Fits In Your Head Write simple code
Open-Closed Principle Open for extension, closed for modification “When requirements
change, extend behaviour by adding new code, not changing code that works”
Open-Closed Principle Open for extension, closed for modification “When requirements
change, the existing code is now wrong! so replace it with code that works” Cruft Accretion Principle
Open-Closed Principle Simple code is easy to change Simple code
is easy to test Simple code is both open and closed Write simple code!
Liskov Substitution Principle “Strong behavioural subtyping” Substitution with a subtype
preserves all “desirable properties” of the original type “Provably undecidable” but useful
Liskov Substitution Principle “There is nothing quite so useless, as
doing with great efficiency, something that should not be done at all.” Stuck in is-a and has-a modelling mindset Drucker’s Warning Principle
Liskov Substitution Principle What about acts-like-a, can-be-used-as-a? Composition is simpler
than inheritance Try to avoid object hierarchies altogether Write simple code!
Interface Segregation Principle Many small interfaces are better than one
big object Design small, role-based interfaces No client depends on methods it doesn’t use
Interface Segregation Principle Practically anything is better than one big
object Design small, role-based classes No client depends on methods it doesn’t use Stable Door Principle This is already true!! —>
Interface Segregation Principle Don’t write big objects in the first
place! Write code that Fits In Your Head If a class needs lots of interfaces, simplify the class! Write simple code!
Dependency Inversion Principle High-level modules should not depend on lower-level
modules Abstractions (e.g. interfaces) should not depend on details (e.g. concrete implementations)
Dependency Inversion Principle Reuse is overrated, design for use! DIP
leads to a different kind of dependency, dependency on DI frameworks! Wrong Goal Principle
Dependency Inversion Principle See how far you get combining simple
classes new is the new new! Assemble into small components that Fit In Your Head Write simple code!
Single Responsibility Open/Closed Liskov Substitution Interface Segregation Dependency Inversion
Single Responsibility Open/Closed Liskov Substitution Interface Segregation Dependency Inversion Too
much to remember!
Single Responsibility Open/Closed Liskov Substitution Interface Segregation Dependency Inversion Write
simple code!