Upgrade to Pro
— share decks privately, control downloads, hide ads and more …
Speaker Deck
Speaker Deck
PRO
Sign in
Sign up for free
Why Every Element of SOLID is Wrong
Daniel Terhorst-North
PRO
January 20, 2017
Technology
127
92k
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
Rethinking Transformation
tastapod
PRO
1
52
CUPID - for joyful coding
tastapod
PRO
3
4.2k
agility at scale - a meeting of mindsets
tastapod
PRO
1
290
SWARMing into action
tastapod
PRO
0
280
Deliberate Advice
tastapod
PRO
3
1k
Governing Agile Delivery
tastapod
PRO
14
300
Complexity
tastapod
PRO
12
780
SWARMing
tastapod
PRO
25
2k
How to break the rules - Cucumber mix
tastapod
PRO
10
850
Other Decks in Technology
See All in Technology
Modern Android dependency injection
hugovisser
1
140
History of the ML system in KARTE
kargo113
1
670
FastConnect 冗長性のベスト・プラクティス
ocise
0
140
oakのミドルウェアを書くときの技のらしきもの
toranoana
0
140
Design for Humans: How to make better modernization decisions
indualagarsamy
2
130
RDRA + JavaによるレジャーSaaSプロダクトの要件定義と実装のシームレスな接続
jjebejj
PRO
3
780
What's Data Lake ? Azure Data Lake best practice
ryomaru0825
2
760
Oracle Base Database Service 技術詳細
oracle4engineer
PRO
3
9.2k
Meet passkeys
satotakeshi
1
130
2024卒_freee_エンジニア職(ポテンシャル採用)_説明資料
freee
0
340
Autonomous Database Cloud 技術詳細 / adb-s_technical_detail_jp
oracle4engineer
PRO
10
18k
フィンテック養成勉強会#23
finengine
0
180
Featured
See All Featured
Large-scale JavaScript Application Architecture
addyosmani
499
110k
Thoughts on Productivity
jonyablonski
43
2.3k
Code Review Best Practice
trishagee
43
9.3k
Embracing the Ebb and Flow
colly
73
3.4k
The Invisible Customer
myddelton
110
11k
Keith and Marios Guide to Fast Websites
keithpitt
404
21k
Code Reviewing Like a Champion
maltzj
506
37k
Fireside Chat
paigeccino
12
1.3k
Design by the Numbers
sachag
271
17k
Bootstrapping a Software Product
garrettdimon
296
110k
We Have a Design System, Now What?
morganepeng
35
3k
ParisWeb 2013: Learning to Love: Crash Course in Emotional UX Design
dotmariusz
100
5.9k
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!