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The scary fairy tale about MVC or How to stop w...
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Andrey Savchenko
May 31, 2013
Programming
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The scary fairy tale about MVC or How to stop worrying and start to write ruby code
Hotcode conference, 5 May 2013
Andrey Savchenko
May 31, 2013
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Transcript
The scary fairy tale about MVC How to stop worrying
and start to write ruby code or
Andrey Savchenko @ptico @ptico_eng Aejis
Cast • Little Red Riding Hood - developer • Grandmother
- customers • The map - MVC • Compass - Rails And others…
nce upon a time, a little girl goes trough the
scary wood to deliver pies to her grandmother. O
here she met the Damn Horrible Human nicknamed «The Wolf»
T
here you are going, little girl? he asked. I’m going
to deliver pies to my grandma – she answered. W –
have a present for you – wolf said. Take this
map and this compass: it works very well for me. I
None
he girl took gifts and moved on. And have lost
in the wood. Because the compass was point to the wolf’s grandmother and map defines the ways not applicable for little girls. T
THE END
Moral: the tools which works for other person may doesn’t
work for you
MVC is a good example
What’s wrong with MVC?
It has only three letters MVC
One of them superfluous MVC
Application should know nothing about representation
Another one means a little bit more than nothing MVC
The controller should delegate the work that needs to be
done to other objects; it coordinates or controls the activity. It should not do much work itself. GRASP controller definition
So, what’s left?
The model M
M
M
M
None
Please, rise your hand if you have this kind of
models
So, this is a moment when we should start writing
the Ruby code
What does it mean?
Lets take a look at our daily gems
carrierwave
state_machine
resque
Ok, i catch the idea, lets start!
Wait a minute - we need some weapons
Metrics
Metrics • WPM - WTFs per minute
Metrics • WPM - WTFs per minute • SLOC/M -
Source lines of code per method
Metrics • WPM - WTFs per minute • SLOC/M -
Source lines of code per method • SLOC/C - Source lines of code per class
Overall complexity ((AVG(SLOC/M) + SLOC/C)^WPM)/100
Overall complexity If you have > 10 – i have
a bad news for you
Principles • SOLID
Principles • SOLID • YAGNI
Principles • SOLID • YAGNI • KISS
Secret weapon: Testability
The simpler your objects to test - the easier they
can be changed and reused
The more complex your objects is - the harder to
test them
Got it! What about strategy?
Strategies:
Use-case strategy
Use-case strategy • Doesn’t work with Rails • Requires to
build your own stack • But once you build this – its bullet-proof
Onion strategy
None
Onion strategy • Do work with Rails • Layer can
be just Plain Old Ruby Object • Layers is hard to naming
Onion strategy Model Controller View
Onion strategy Model Controller View Presenter
Onion strategy Model Controller View Presenter Form object
Onion strategy Model Controller View Presenter Form object Repository
Onion strategy Model Controller View Presenter Form object Repository Service
Onion strategy Model Controller View Presenter Form object Repository Service
Validator
Attribution: http://www.flickr.com/photos/42255449@N00/7177978063/ http://www.flickr.com/photos/normanbleventhalmapcenter/2674605704/ Thank you!
Questions? Andrey Savchenko Aejis* * we are hiring** ** if
you understand the problem described in talk