How to decouple, how to develop, how to choose the correct technology, few DDD concepts, and why BDD is so important. How to Think... http://rome.codemotionworld.com/2014/wp-content/themes/codemotion/detail-talk.php?detail=75

1. Codemotion ROME
@bit_shark
Andrea Giuliano
Think horizontallydo not use lighters to open beers
Giulio De Donato
andreagiuliano.it welcometothebundle.com
@liuggio
11-12 april 2014

2. Think
horizontally
@bit_shark @liuggio#codemotion
hint
We won't use technicisms and acronyms.
Please see the references, we have had a lot of inspiration

3. thinking ideal
@bit_shark @liuggio#codemotion
Given an application with certain requirements
which is the technology that fit the application requirements?

4. thinking real
@bit_shark @liuggio#codemotion
Given an application with certain requirements,
I’m guru on Java I’ll use Java.

5. think too much…
… at the same technology
@bit_shark @liuggio#codemotion
What’s wrong here?
I’m developing a tech-centric application
I’m fitting business requirements with technical boundaries

6. rethink to
the origin
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But what about our preferred technology?
Was it the coolest? The most requested for working? Or trivially the simplest?

7. think about
laziness
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A developer should choose
not the simplest tech
The developer laziness drive the
developer to reuse its code!

8. different thoughts
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A language can lack on some structural characteristic
(polymorphism, strong typing)

9. think with ease
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The success of a language is it’s distributability
(cheap, easy, zero-conf)?

10. a thought for thought
@bit_shark @liuggio#codemotion
There are successful application written in lacking languages
The success of the business make the success of the application

11. thinking relational
@bit_shark @liuggio#codemotion
EAV
thousand of libraries choose the relational
model instead of schemaless
• simplicity to distribute and install
• even though some arguable tech detail

12. think to aim
the success
@bit_shark @liuggio#codemotion
nosql
Using the right technology in some
cases could lead to a wrong choice

13. Shaggio theorem
@bit_shark @liuggio#codemotion
Hypothesis: supposing a developer knows every technology
and make a good choice for a complex application
Thesis: whatever will be the choice could be the wrong choice
…we are thinking to the app
as a one big global ‘entity'

14. think modular
@bit_shark @liuggio#codemotion
we want to split the application in as many
as possible modules choosing the “right”
technology for each module

15. think…
@bit_shark @liuggio#codemotion
• Split the business needs in subsets… a subset could be composed by services...
• Spit and conquer and Object Oriented Design
• If you have to implement a complex system, don’t implement a complex
system, implement a lot of simple systems

16. think procedural
@bit_shark @liuggio#codemotion
developing with procedural is misleading, at the beginning
you feel powerful, fast…

17. think WTF!
@bit_shark @liuggio#codemotion
• How many times you will modify the application, did you think about Maintenance costs?
• Procedural is when you create a fast program (at the beginning) but difficult to maintain.
“Tragically, the very same forces that make it so easy
to add new features to a brand new Rails
application are the ones that start to hold you back
as the number of features grows.” cit. Matt Wynne

18. think connected
Time
Feature
😊
😁
😰
🏃
@bit_shark @liuggio#codemotion

19. think connected
Time
Feature
😊
😁
😰
🏃
@bit_shark @liuggio#codemotion
• The procedural code is sick with a disease called "code connected”
• Object-oriented programming is not immune
• Time increases exponentially with the addition of new features.

20. think “Operation”
@bit_shark @liuggio#codemotion
All the programs are difficult to maintain, but decoupled software is easier
How to understand if my code is decoupled?
If you modify here and you don’t break over there.

21. Time
Feature
think maintainability
@bit_shark @liuggio#codemotion
TDD

22. Time
Feature
think maintainability
@bit_shark @liuggio#codemotion
TDD
• Modularity is the main concept of Object Oriented Design
• The trend has changed (90 years ago), now we have to focus on maintainability
• The overhead of testing before code is smaller than you think and the real adding
value is the way you develop better your application

23. Think back to ‘89
@bit_shark @liuggio#codemotion
responsability driven approach!
SOLID principles
• R. Wirfs-Brock, B. Wilkerson, “Object-Oriented Design: A Responsibility-Driven Approach”
• Single responsibility principle Uncle Bob
• Create a module coupling things that changes together?
• Modules that communicates, but how?

24. think tell don’t ask
Matt Wayne, Uncle Bob, Alec Sharp and Martin Fowler
@bit_shark @liuggio#codemotion

25. think behaviour
@bit_shark @liuggio#codemotion
dependency injection
• Modules that communicate via protocols
• Modules that exhibit a behavior not their data
• Data are the guts of the module, they must not be exposed
• All the public functions are API, let's take care and give them a meaning.
• Each module should have its own explicit dependencies

26. think and code
@bit_shark @liuggio#codemotion
1. An employee has always a name and a salary!
2. The salary is always greater than zero!
3. A company could add an employee

27. think and code
@bit_shark @liuggio#codemotion
1. An employee has always a name and a salary!
2. The salary is always greater than zero!
3. A company could add an employee

28. @bit_shark @liuggio#codemotion
think invariant
1. An employee has always a name and a salary!
2. The salary is always greater than zero!
3. A company could add an employee

29. @bit_shark @liuggio#codemotion
think consistent
1. An employee has always a name and a salary!
2. The salary is always greater than zero!
3. A company could add an employee

30. @bit_shark @liuggio#codemotion
think business language
3. A company could hire an employee
1. An employee has always a name and a salary!
2. The salary is always greater than zero!
3. A company could add an employee

31. think behaviour not data
@bit_shark @liuggio#codemotion
Bdd!
specification

32. think
Behaviour
Driven
Development
@bit_shark @liuggio#codemotion
That's why with BDD (stories and specs) you
are more forced not to test the application
but you focus on describe the behaviors.
With BDD you tend to describes the behavior
before coding, you specify what a function
should do.

33. think behaviour
defer implementation
@bit_shark @liuggio#codemotion

34. think onion
@bit_shark @liuggio#codemotion
hexagonal
Database as implementation detail
Framework as implementation detail

35. think to clean the Architecture
Application goal: separation of concerns
Easy substitution of obsolete elements without affecting others components of the architecture

36. Andrea Giuliano
@bit_shark
andreagiuliano.it
Giulio De Donato
@liuggio
welcometothebundle.com
T h i n k y o u !
Thank

37. References
https://farm3.staticflickr.com/2491/4193434786_306120fe90_b.jpg
https://farm8.staticflickr.com/7185/13732796883_58bb40fae9_b.jpg
https://farm8.staticflickr.com/7290/12859759305_51e8685d43_b.jpg
https://www.flickr.com/photos/lovezonero/5304831965/sizes/l/
http://i.imgur.com/xl9v1on.jpg
https://farm4.staticflickr.com/3404/3633209399_467123a6ca_o.jpg
https://farm1.staticflickr.com/188/391815999_2725ca688c_b.jpg
https://farm2.staticflickr.com/1116/1486403962_d055d8b1f9_o.jpg
https://farm4.staticflickr.com/3055/2852526965_bee2642e0f_o.jpg
- Growing Object-Oriented Software by Guided by Tests, Steve Freeman, Nat Pryce
- Implementing Domain-Driven Design by Vaughn Vernon
- Unbreakable Domain Models by Mathias Verraes
- Uncle Bob the clean Architecture http://blog.8thlight.com/uncle-bob/2012/08/13/
the-clean-architecture.html
- DDD community
- Matt Wayne GoRuCo 2012 Hexagonal Rails by Matt Wynne
- Implementing Domain-Driven Design with Spring and vFabric Wes Williams, Vaughn
Vernon
- The RSpec Book Behaviour-Driven Development with RSpec, Cucumber, and Friends
by David Chelimsky, Dave Astels, Zach Dennis, Aslak Hellesøy, Bryan Helmkamp,
Dan North
- Alberto Brandolini http://www.slideshare.net/ziobrando/
https://farm6.staticflickr.com/5134/5449083311_9a856145fa_b.jpg
https://farm3.staticflickr.com/2583/3752448573_4cc6a2698a_b.jpg
https://farm4.staticflickr.com/3325/3420223723_2805816861_b.jpg
https://farm1.staticflickr.com/118/313590022_25c580474c_b.jpg
https://farm4.staticflickr.com/3274/2886945884_8dfa5d849f_b.jpg
https://farm5.staticflickr.com/4013/4290367973_c58749d73f_b.jpg
https://farm9.staticflickr.com/8327/8091221482_dce187e288_b.jpg
https://farm1.staticflickr.com/48/108484055_b07800b7c7_b.jpg
https://farm8.staticflickr.com/7115/7445550970_32ac507395_b.jpg
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