Understanding and Applying the SOLID Principles

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Hierarchy of Pattern Knowledge 🔗

Design Patterns
- Strategy Pattern
  Define a family of algorithms, encapsulate each one, and make them interchangeable.
  A client using a strategy can change that strategy while it is in use.
Object-Oriented Principles
- Encapsulate what varies.
- Favor composition over inheritance.
- Program to interfaces rather than implementations.
Object-Oriented Basics
- Classes and objects
- Inheritance
- Polymorphism
- Encapsulation
- Abstraction

Design Smells 🔗

Signs and symptoms of poor design.

Name	Symptom
Rigidity	The system is difficult to change. Every change triggers an endless sequence of further changes.
Fragility	Changing one part of the system breaks several other, unrelated parts.
Immobility	It is difficult to separate the system into components that can be reused in other systems.
Viscosity	Viscosity is high when adding a workaround is easier than adding code that follows the design.
Needless Complexity	There are many complicated code structures that are not needed now but might be useful someday.
Needless Repetition	The code looks as if two programmers wrote it using copy and paste.
Opacity	The complexity of the expression creates particular difficulties in understanding the original author's intent.

Dependency Management 🔗

Design smells arise from

unmanaged dependencies

.

Unmanaged dependencies

A
tangled mass of coupling
: spaghetti code.

Object-oriented languages provide various mechanisms for managing dependencies.

Interfaces: contracts that reduce dependencies between objects.
Polymorphism: enables a module to invoke methods dynamically.

Object-Oriented Design Principles 🔗

The SOLID principles by Robert C. Martin
The GRASP principles by Craig Larman
Program to interfaces rather than implementations (Interface-Oriented Programming).
Favor object composition over class inheritance.
Encapsulate what varies.

The SOLID principles 🔗

S
ingle Responsibility Principle —
SRP
O
pen-Closed Principle —
OCP
L
iskov Substitution Principle —
LSP
I
nterface Segregation Principle —
ISP
D
ependency Inversion Principle —
DIP

Understanding and Applying the SOLID Principles | PromleeBlog