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
20 Years of BDD
tastapod
PRO
0
88
The best programmer I know
tastapod
PRO
2
390
How to bake a change
tastapod
PRO
0
540
The Most Dangerous Phrase
tastapod
PRO
7
6.3k
Rethinking Transformation
tastapod
PRO
1
420
CUPID - for joyful coding
tastapod
PRO
5
7.6k
agility at scale - a meeting of mindsets
tastapod
PRO
1
600
SWARMing into action
tastapod
PRO
0
400
Deliberate Advice
tastapod
PRO
3
1.5k
Other Decks in Technology
See All in Technology
Rustから学ぶ 非同期処理の仕組み
skanehira
1
140
5年目から始める Vue3 サイト改善 #frontendo
tacck
PRO
3
220
自作JSエンジンに推しプロポーザルを実装したい!
sajikix
1
190
未経験者・初心者に贈る!40分でわかるAndroidアプリ開発の今と大事なポイント
operando
5
710
「どこから読む?」コードとカルチャーに最速で馴染むための実践ガイド
zozotech
PRO
0
520
AI開発ツールCreateがAnythingになったよ
tendasato
0
130
企業の生成AIガバナンスにおけるエージェントとセキュリティ
lycorptech_jp
PRO
2
190
CDK CLIで使ってたあの機能、CDK Toolkit Libraryではどうやるの?
smt7174
4
190
品質視点から考える組織デザイン/Organizational Design from Quality
mii3king
0
210
Terraformで構築する セルフサービス型データプラットフォーム / terraform-self-service-data-platform
pei0804
1
190
LLM時代のパフォーマンスチューニング:MongoDB運用で試したコンテキスト活用の工夫
ishikawa_pro
0
160
複数サービスを支えるマルチテナント型Batch MLプラットフォーム
lycorptech_jp
PRO
1
780
Featured
See All Featured
Templates, Plugins, & Blocks: Oh My! Creating the theme that thinks of everything
marktimemedia
31
2.5k
Speed Design
sergeychernyshev
32
1.1k
Typedesign – Prime Four
hannesfritz
42
2.8k
XXLCSS - How to scale CSS and keep your sanity
sugarenia
248
1.3M
Keith and Marios Guide to Fast Websites
keithpitt
411
22k
Fashionably flexible responsive web design (full day workshop)
malarkey
407
66k
Helping Users Find Their Own Way: Creating Modern Search Experiences
danielanewman
29
2.9k
A Tale of Four Properties
chriscoyier
160
23k
Build The Right Thing And Hit Your Dates
maggiecrowley
37
2.9k
RailsConf 2023
tenderlove
30
1.2k
Gamification - CAS2011
davidbonilla
81
5.4k
Learning to Love Humans: Emotional Interface Design
aarron
273
40k
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!