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

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WHAT ABOUT?

Don't Be Stupid, Grasp Solid

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AGENDA

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STUPID CODE

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Stupid code, seriously?

STUPID CODE

• Singleton

• Tight coupling

• Untestability

• Premature optimization

• Indescriptive naming

• Duplication

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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

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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.

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UNTESTABILITY

• The unit tests should be easy

• Untestability is cause by tight coupling

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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.

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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

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DUPLICATION

• DRY – don’t repeat yourself

• KISS – keep it simple(stupid)

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

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CODING KATA - INTRO

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CODING KATA - INTRO

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CODING KATA - INTRO

• KATA – came from martial arts

• Dave Thomas – has introduced Kata as learning technique

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DEMO - I

• Fibonacci – Kata TDD

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SOLID PRINCIPLES

• Single Responsibility Principle - SRP

• Open-Closed Principle - OCP

• Liskov Principle - LSP

• Interface Segregation Principle - ISP

• Dependency Inversion Principle - DIP

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JENGA GAME

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SOLID

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SINGLE RESPONSIBILITY PRINCIPLE

A class should have

only one reason to

change.

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SINGLE RESPONSIBILITY

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SINGLE RESPONSIBILITY - TIPS

• Split big classes

• Use layers

• Avoid god classes

• Write straightforward comments

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OPEN-CLOSED PRINCIPLE - OCP

Software entities

should be open for

extension and closed

for modification.

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OPEN-CLOSED PRINCIPLE

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OPEN-CLOSED PRINCIPLE - TIPS

• Make all members variables private

• No global variables

• Avoid setters (as much as possible)

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LISKOV SUBSTITUTION PRINCIPLE

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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.

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LISKOV SUBSTITUTION PRINCIPLE

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LISKOV SUBSTITUTION PRINCIPLE

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LISKOV SUBSTITUTION PRINCIPLE

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INTERFACE SEGREGATION PRINCIPLE

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INTERFACE SEGREGATION PRINCIPLE

•ISP states

that many client-

specific interfaces are

better than one general-

purpose interface.

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INTERFACE SEGREGATION PRINCIPLE

•You should not have to

implement methods that you

don't use. Enforcing ISP

gives you low coupling,

and high cohesion.

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DEPENDENCY INVERSION PRINCIPLE

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DEPENDENCY INVERSION PRINCIPLE

•DIP has 2 key points:

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DEPENDENCY INVERSION PRINCIPLE

•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

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DEPENDENCY INVERSION PRINCIPLE

•Note•DIP is not the same like

Dependency Injection

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DEPENDENCY INVERSION PRINCIPLE

•Note•Dependency Injection is about

how one object knows about

another dependent object.

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DEPENDENCY INVERSION PRINCIPLE

•Note•In other words, it is about how

one object acquires a

dependency.

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DEPENDENCY INVERSION PRINCIPLE

•http://stackoverflow.com/questi

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

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ON MORE THING…

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SMILES

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SMILES

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

program frustrate him for a lifetime - Muhammad Waseem

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SMILES

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

program frustrate him for a lifetime - Muhammad Waseem

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

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SMILES

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

program frustrate him for a lifetime - Muhammad Waseem

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

course.

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SMILES

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

program frustrate him for a lifetime - Muhammad Waseem

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

course.

• Walking on water and developing software to specification are

easy ….

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SMILES

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

program frustrate him for a lifetime - Muhammad Waseem

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

course.

• Walking on water and developing software to specification are

easy as long as both are frozen.

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CONCLUSIONS

• Use your brain

• Writing SOLID code is not that hard

• Avoid STUPID code

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QUESTIONS?

THANK YOU!

March 28, 2015

FLORIN OLARIU

florin.olariu@centric.eu