From Stupid to Solid Code

FROM STUPID TO SOLID CODE

March 28, 2015

FLORIN OLARIU

CENTRIC IT SOLUTION ROMANIA

ABOUT ME

• I’m working in field since 1996

• I’ve started as Java developer– I’m SCJP certified

• I’ve continued as team leader for a mixt team(Java/.NET

developers working with Waterfall methodologies)

• I’ve continued with .NET technologies since in 2003– I’m MCPD Windows Forms 2.0 certified – since 2006

– I’m MCPD Windows Forms 4.0 certified – since 2010

– I’m MCPD Web Forms 4.0 certified – since 2011

• Technical Lead/Scrum Master in Centric

March 28, 2015TITLE PRESENTATION

WHAT ABOUT?

Don't Be Stupid, Grasp Solid


AGENDA


STUPID CODE


Stupid code, seriously?

STUPID CODE

• Singleton

• Tight coupling

• Untestability

• Premature optimization

• Indescriptive naming

• Duplication


SINGLETON

• The most well-known pattern used• Program using global state are very difficult to test

• Program that rely on global state hide their dependencies


TIGHT COUPLING

• Aka : strong coupling

• The main goal is to reduce coupling between modules• Difficult to reuse

• Hard to test

• Coupling - the degree to which each program module relies

on each one of the other modules.


http://en.wikipedia.org/wiki/Coupling_(computer_programming)

UNTESTABILITY

• The unit tests should be easy

• Untestability is cause by tight coupling


PREMATURE OPTIMIZATION

• Donald Knuth said: premature optimization is the root of all

evil. There is only cost, and no benefit.

• Two rules to optimize an application:• don't do it;

• (for experts only!) don't do it yet.


INDESCRIPTIVE NAMING

• Programming languages are for humans.

• “Any fool can write code that a computer can understand.

Good programmers write code that humans can understand.”

– Martin Fowler


DUPLICATION

• DRY – don’t repeat yourself

• KISS – keep it simple(stupid)

• Be lazy in the right way – write code only once.


CODING KATA - INTRO


CODING KATA - INTRO


CODING KATA - INTRO

• KATA – came from martial arts

• Dave Thomas – has introduced Kata as learning technique


DEMO - I

• Fibonacci – Kata TDD


SOLID PRINCIPLES

• Single Responsibility Principle - SRP

• Open-Closed Principle - OCP

• Liskov Principle - LSP

• Interface Segregation Principle - ISP

• Dependency Inversion Principle - DIP


JENGA GAME


SOLID


SINGLE RESPONSIBILITY PRINCIPLE

A class should have

only one reason to

change.


SINGLE RESPONSIBILITY


SINGLE RESPONSIBILITY - TIPS

• Split big classes

• Use layers

• Avoid god classes

• Write straightforward comments


OPEN-CLOSED PRINCIPLE - OCP

Software entities

should be open for

extension and closed

for modification.


OPEN-CLOSED PRINCIPLE


OPEN-CLOSED PRINCIPLE - TIPS

• Make all members variables private

• No global variables

• Avoid setters (as much as possible)


LISKOV SUBSTITUTION PRINCIPLE



• LSP states that objects in a

program should

be replaceable with

instances of their subtypes

without altering the

correctness of the program.








INTERFACE SEGREGATION PRINCIPLE



•ISP states

that many client-

specific interfaces are

better than one general-

purpose interface.



•You should not have to

implement methods that you

don't use. Enforcing ISP

gives you low coupling,

and high cohesion.


DEPENDENCY INVERSION PRINCIPLE



•DIP has 2 key points:



•DIP has 2 key points:–Abstractions should not depend upon

details – both should depend on

abstractions

–Details should not depend upon

abstraction – details should depend

on abstractions



•Note•DIP is not the same like

Dependency Injection



•Note•Dependency Injection is about

how one object knows about

another dependent object.



•Note•In other words, it is about how

one object acquires a

dependency.


http://martinfowler.com/articles/dipInTheWild.html


•http://stackoverflow.com/questi

ons/6766056/dip-vs-di-vs-ioc


http://stackoverflow.com/questions/6766056/dip-vs-di-vs-ioc

ON MORE THING…


SMILES


SMILES

• Give a man a program, frustrate him for a day. Teach a man to

program frustrate him for a lifetime - Muhammad Waseem


SMILES



• What is the object-oriented way of getting rich?


SMILES



• What is the object-oriented was of getting rich? Inheritance of

course.


SMILES




course.

• Walking on water and developing software to specification are

easy ….


SMILES




course.

• Walking on water and developing software to specification are

easy as long as both are frozen.


CONCLUSIONS

• Use your brain

• Writing SOLID code is not that hard

• Avoid STUPID code


QUESTIONS?

THANK YOU!

March 28, 2015

FLORIN OLARIU

[email protected]

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