SOLIDClean code for mere mortals

{What is software development?

‹ Software development is not (only) programming

‹ Agile Software Development: Principles, Patterns, and Practices

‹ The Pragmatic Programmer

‹ Manifesto for Software Craftsmanship

Software requirements

‹ Notoriously fluid

‹ Changes in scope

‹ Changes in functionalities

‹ Changes in environments

‹ The only constant is change

‹ We should embrace change!

{

{Software Rot

‹ Occurs to any software that survives the first version

‹ Rigidity

‹ Fragility

‹ Immobility

‹ Viscosity

SOLID Principles

‹ Introduced by Robert C. Martin (Uncle Bob)

‹ An acronym of acronyms

‹ Not a piece of code

‹ Tool for “code smell” detection

{

SOLID Principles

‹ Single Responsibility Principle

‹ Open Closed Principle

‹ Liskov Substitution Principle

‹ Interface Segregation Principle

‹ Dependency Inversion Principle

{

SOLID

‹ Single Responsibility Principle

‹ Single Level of abstraction

‹ Just one reason to change

‹ Antithesis of the “God” object

{

SRP IN ACTION

SOLID

‹ Open Closed Principle

‹ Inspired from work on Eiffel

‹ Open for extensions

‹ Closed for modification

‹ Use polymorphic behaviours

{

OCP IN ACTION

SOLID

‹ Liskov Substitution Principle

‹ Named after Barbara Liskov

‹ Subclasses should be substitutable for their base classes.

‹ Design by Contract

‹ A Circle is not an Ellipse

{

LSP IN ACTION

SOLID

‹ Interface Segregation Principle

‹ It’s not always about the `interface` keyword

‹ An interface should have a single purpose

‹ An interface should define a client

{

ISP IN ACTION

SOLID

‹ Dependency Inversion‹ Depend upon abstractions.‹ Do not depend upon concretions.‹ Object creation problems – use

object factories.‹ The principle behind Inversion-of-

control and Dependency Injection

{

DIP IN ACTION

Bonus Principle: YAGNI

‹ You Ain’t Gonna Need It

‹ Just-in-time implementation

‹ Avoid architecture astronauts

‹ Simpler code is easier to refactor

‹ Keep it as simple as possible, but not simpler

{

Questions?• Complete the electronic evaluation

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