emergent design - php jo'burg 2015

c a k e s , s h o w e r s a n d e l e c t r i c i a n s

EMERGENT DESIGN

Rouan Wilsenach @rouanw

thoughtworks.com

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It is not enough for code to work.

- Robert Martin

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WHY DESIGN ?

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11 ANDY GREENBERG/WIRED

12Steve Jurvetson

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Easy to learn Fast to changeFewer bugs

WHY EMERGENT ?

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15https://www.flickr.com/photos/jshj/4619958228

16https://www.flickr.com/photos/chrisny2/4637837938

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Build. Measure. Learn.

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emerge

verb • become apparent

https://www.flickr.com/photos/schnappi/2321628609

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not

become well-designed

https://www.flickr.com/photos/evaysucamara/5438832695

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a change made in analysis for $1 would cost thousands

to fix in production

- The change curve

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a change made in analysis for $1 would cost thousands

to fix in production

- The change curve

SIMPLICITYWhat is good design?

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Why is this so hard? - Every developer, ever

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a system made out of genuinely simple parts, is going to be able to

affect the greatest change with the least work

- Rich Hickey

25http://martinfowler.com/bliki/BeckDesignRules.html

AWAY FROM !

THE CODE

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Talk about it

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Draw something

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Know your challenges

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Where are we going?

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IN FRONT OF !

THE CODE

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refactoring

noun • a change made to the internal structure of software to

make it easier to understand and cheaper to modify without

changing its observable behaviour

http://martinfowler.com/bliki/DefinitionOfRefactoring.html

BEFOREPreparatory refactoring

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Make the change easy (warning: this may be hard), then make the easy change

- Kent Beck

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You must kill all your darlings

- William Faulkner

DURINGContinuous refactoring

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Don’t forget the last step

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Talk through it

AFTERTake a step back

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When writing code we should always be

thinking of the reader - Martin Fowler

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Always leave the campground cleaner than you found it.

- The boy scout rule, Robert Martin

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Perfect is the enemy of good.

- Voltaire

SOME TECHNIQUES

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Code smells

https://www.flickr.com/photos/ericparker/11245157393

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Side effects

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Refactor to patterns

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Clean code is a hygiene factor

https://www.flickr.com/photos/tambako/2515141429

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There are only two hard things in Computer Science: cache invalidation

and naming things. - Phil Karlton

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Small things are easier to understand

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SOLID

S ingle responsibility principle

Open/closed principle…

RECAPAgain! Again!

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Build. Measure. Learn.

Working code is not enough

change the change curve

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Simplicity

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In front of the code

Away from the code

SOME RESOURCES

Articles

• http://martinfowler.com/articles/designDead.html

• http://martinfowler.com/bliki/BeckDesignRules.html

• bit.ly/nf-ead-all (Neal Ford)

Videos

• http://www.infoq.com/presentations/Simple-Made-Easy (Rich Hickey)

• https://vimeo.com/16955608 (Neal Ford)

Books

• http://www.amazon.com/Clean-Code-Handbook-Software-Craftsmanship/dp/0132350882 (Uncle Bob)

• http://www.amazon.com/Extreme-Programming-Explained-Embrace-Edition/dp/0321278658 (Kent Beck)

News

• http://www.wired.com/2015/07/hackers-remotely-kill-jeep-highway/

• http://motherboard.vice.com/en_uk/read/how-is-critical-life-or-death-software-tested

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a m e t a p h o r m a s h - u p

EMERGENT DESIGN

Rouan Wilsenach @rouanw

thoughtworks.com