The SOLID Principles of Object-Oriented Design
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Master SOLID design principles to build highly maintainable, testable, and robust object-oriented software architectures.
#oop#architecture#design-patterns#solid#best-practices
What is SOLID?
SOLID is an acronym representing five core design principles for building robust software architectures:
- Single Responsibility Principle (SRP): A class should have one, and only one, reason to change.
- Open/Closed Principle (OCP): Software entities (classes, modules) should be open for extension but closed for modification.
- Liskov Substitution Principle (LSP): Subtypes must be substitutable for their base types without altering program correctness.
- Interface Segregation Principle (ISP): Clients should not be forced to depend on interfaces they do not use (prefer multiple thin interfaces over one bloated interface).
- Dependency Inversion Principle (DIP): High-level modules should not depend on low-level modules; both should depend on abstractions (interfaces).
DIP Violation & Refactored Solution (Python)
python
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# ❌ VIOLATION: High-level LightBulb depends on low-level Switch directly
class LightBulb:
def turn_on(self): pass
class Switch:
def __init__(self, bulb: LightBulb):
self.bulb = bulb # Direct dependency coupling
#
# REFACTORED: Both depend on a common abstract interface
from abc import ABC, abstractmethod
class Switchable(ABC):
@abstractmethod
def turn_on(self): pass
class BetterLightBulb(Switchable):
def turn_on(self): print("Bulb glowing!")
class BetterSwitch:
def __init__(self, device: Switchable):
self.device = device # Decoupled! Fits any Switchable device (bulbs, fans, heaters)Discussion
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