OOPS Question
Explain SOLID principles in Object Oriented Design .

Question

OOPS Question

Explain SOLID principles in Object Oriented Design .

Accepted Answer

The SOLID principle is an acronym of the five principles which is given below :

1) Single Responsibility Principle (SRP)
2) Open/Closed Principle
3) Liskov’s Substitution Principle (LSP)
4) Interface Segregation Principle (ISP)
5) Dependency Inversion Principle (DIP)

Uses of SOLID design principles :

1) The SOLID principle helps in reducing tight coupling.
2) Tight coupling means a group of classes are highly dependent on one another which we should avoid in our code.
3) Opposite of tight coupling is loose coupling and our code is considered as a good code when it has loosely-
coupled classes.
4) Loosely coupled classes minimize changes in your code, helps in making code more reusable,
maintainable,flexible and stable.

Explaining the 5 SOLID principles one by one :

1) Single Responsibility Principle : This principle states that “a class should have only one reason to change” which
means every class should have a single responsibility or single job or single purpose.
Use layers in your application and break God classes into smaller classes or modules.

2) Open/Closed Principle : This principle states that “software entities (classes, modules, functions, etc.) should be
open for extension, but closed for modification” which means you should be able to extend a class behavior, without
modifying it. Using this principle separates the existing code from the modified code so it provides better stability,
maintainability and minimizes changes as in your code.

3) Liskov’s Substitution Principle : According to this principle “Derived or child classes must be substitutable for their
base or parent classes“. This principle ensures that any class that is the child of a parent class should be usable in
place of its parent without any unexpected behavior.

4) Interface Segregation Principle : This principle is the first principle that applies to Interfaces instead of classes in
SOLID and it is similar to the single responsibility principle. It states that “do not force any client to implement an
interface which is irrelevant to them“. Here your main goal is to focus on avoiding fat interface and give preference to
many small client-specific interfaces.

5) Dependency Inversion Principle : Two key points are here to keep in mind about this principle
a) High-level modules/classes should not depend on low-level modules/classes. Both should depend upon
abstractions.
b) Abstractions should not depend upon details. Details should depend upon abstractions.

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