1. SOLID Principles with Easy Examples | OOPs SOLID Principles Interview Question - Low Level Design

Concept && Coding - by Shrayansh

26 May 202219:02

Summary

TLDRThe video script discusses the SOLID principles of object-oriented programming, which are crucial for writing understandable, flexible, and maintainable code. It provides examples of how each principle, such as Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, and Dependency Inversion, can be applied to avoid code duplication and complexity. The script uses relatable examples like a market invoice system and a keyboard interface to illustrate these principles in action, emphasizing the importance of good coding practices for software development.

Takeaways

📘 The video discusses the SOLID principles of object-oriented programming, which are guidelines to make software designs more understandable, flexible, and maintainable.
🔑 The Single Responsibility Principle is highlighted, emphasizing that a class should have only one reason to change, meaning one job or responsibility.
🔄 Open/Closed Principle is explained, advocating for classes to be open for extension but closed for modification, allowing the addition of new functionality without altering existing code.
🔗 The Liskov Substitution Principle is touched upon, stating that derived classes should be substitutable for their base classes without affecting the correctness of the program.
🔄 Dependency Inversion Principle is mentioned, suggesting that high-level modules should not depend on low-level modules but rather on abstractions (e.g., interfaces).
🛠️ The video provides examples to illustrate the principles, such as creating an Invoice class that calculates total price based on price and quantity, demonstrating the Single Responsibility Principle.
📚 The script mentions the importance of keeping classes focused on a single task to prevent the need for changes in multiple places when requirements shift.
📈 The concept of extending functionality without modifying existing code is illustrated through examples, such as adding new features to a class without altering its core logic.
🔍 The video script addresses the challenges of adhering to the SOLID principles in real-world scenarios, such as when changes in business requirements necessitate breaking the principles.
🛑 The script uses the example of a Vehicle class to explain how the Liskov Substitution Principle can be violated if a subclass does not maintain the same behavior as its parent class.
🔗 The Dependency Inversion Principle is exemplified by showing how implementing interfaces can lead to more flexible and maintainable code by reducing direct dependencies between classes.

Q & A

What is the main topic of the video script?
-The main topic of the video script is the SOLID principles of object-oriented programming, with a focus on explaining each principle and providing examples of how they can be applied in software development.
What does SOLID stand for in software development?
-SOLID is an acronym for five design principles intended to make software designs more understandable, flexible, and maintainable. The principles are Single Responsibility, Open/Closed, Liskov Substitution, Interface Segregation, and Dependency Inversion.
What is the Single Responsibility Principle?
-The Single Responsibility Principle states that a class should have only one reason to change, meaning it should only have one job or responsibility.
Can you provide an example from the script that illustrates the Single Responsibility Principle?
-An example given in the script is a class named 'Invoice' that calculates the total price based on the price and quantity of items. This class follows the Single Responsibility Principle as its only job is to handle the calculation logic.
What is the Open/Closed Principle?
-The Open/Closed Principle states that software entities should be open for extension but closed for modification, meaning that you should be able to extend the functionality without changing the existing code.
How does the script explain the Liskov Substitution Principle?
-The script does not explicitly mention the Liskov Substitution Principle, but it can be inferred from the discussion on extending classes without modifying them, which aligns with the principle that subclasses should be substitutable for their base classes without affecting the correctness of the program.
What does the Interface Segregation Principle suggest?
-The Interface Segregation Principle suggests that no client should be forced to depend on methods it does not use, which means that interfaces should be small and client-specific.
Can you give an example from the script that demonstrates the Dependency Inversion Principle?
-While the script does not provide a direct example, the Dependency Inversion Principle can be related to the discussion on depending on abstractions rather than concrete implementations, which is a way to reduce the dependency of one class on another.
What is the purpose of the examples provided in the script?
-The purpose of the examples in the script is to illustrate how the SOLID principles can be applied in practical programming scenarios to create more maintainable, flexible, and understandable code.
How does the script address the issue of code duplication?
-The script addresses the issue of code duplication by emphasizing the benefits of the SOLID principles, such as reducing complexity and avoiding duplication by adhering to the Single Responsibility Principle and Open/Closed Principle.
What is the significance of understanding SOLID principles in software development?
-Understanding SOLID principles is significant in software development as it helps in creating a robust and scalable architecture, making the code easier to maintain, extend, and understand, which ultimately leads to higher quality software.

Outlines

00:00

📘 Introduction to SOLID Principles

The first paragraph introduces the SOLID principles of object-oriented programming, which are crucial for creating understandable, flexible, and maintainable code. The speaker discusses the importance of these principles in software development and provides a brief overview of the Single Responsibility Principle, one of the five SOLID principles. The paragraph sets the stage for a deeper dive into each principle through examples and explanations.

05:02

🔍 Exploring the Open/Closed Principle

The second paragraph delves into the Open/Closed Principle, emphasizing that software entities should be open for extension but closed for modification. The speaker uses the example of a dance class to illustrate how this principle can be applied to create flexible and adaptable code. The paragraph discusses the benefits of adhering to this principle, such as preventing the need for changes in existing code when new functionality is required.

10:03

🛠 The Liskov Substitution Principle

In the third paragraph, the Liskov Substitution Principle is explored, which states that derived classes should be substitutable for their base classes without affecting the correctness of the program. The speaker provides an example involving a motorcycle and its engines to demonstrate how this principle ensures that objects of a superclass can be replaced with objects of a subclass without causing errors or unexpected behavior in the program.

15:05

🔗 Understanding the Interface Segregation Principle

The fourth paragraph discusses the Interface Segregation Principle, which advises that no client should be forced to depend on methods it does not use. The speaker explains this principle with the example of a restaurant employee who should not be burdened with unrelated tasks. The paragraph highlights the importance of creating fine-grained interfaces that allow clients to depend only on the methods they need, thus improving the maintainability and flexibility of the code.

Mindmap

Keywords

💡SOLID Principles

SOLID is an acronym for five design principles that intend to make software designs more understandable, flexible, and maintainable. In the context of the video, SOLID principles are likely discussed to emphasize good coding practices that lead to more robust and scalable applications. The script mentions 'SOLID' explicitly, indicating it as a central theme.

💡Single Responsibility Principle

This principle states that a class should have only one reason to change, meaning it should only have one job or responsibility. In the video, the concept is exemplified through the idea of a class that calculates an invoice, which is a single task and thus adheres to this principle.

💡Open/Closed Principle

This principle suggests that software entities should be open for extension but closed for modification. The script discusses this in the context of adding new features to a class without modifying its existing code, which is a core aspect of this principle.

💡Liskov Substitution Principle

This principle is about ensuring that derived classes can be substituted for their base classes without affecting the correctness of the program. The script seems to touch on this by mentioning the importance of child classes being able to replace their parent classes without issues.

💡Interface Segregation Principle

This principle argues for the segregation of an interface into client-specific interfaces, thus making it more specific to the client's needs. The script may refer to this principle when discussing the design of interfaces that are tailored to particular classes and not overly generalized.

💡Dependency Inversion Principle

This principle involves two points: high-level modules should not depend on low-level modules, and both should depend on abstractions. The script hints at this principle when it talks about classes depending on interfaces rather than concrete implementations.

💡Invoice

An invoice is a document issued by a seller to a buyer, indicating the products, quantities, and agreed prices for products or services. In the script, the invoice is used as an example to illustrate the application of the Single Responsibility Principle.

💡Class

In object-oriented programming, a class is a blueprint for creating objects. It is a template that defines the properties and methods that the object will have. The script frequently refers to classes and their responsibilities, especially in the context of the SOLID principles.

💡Method

A method is a function that is associated with an object or a class. It describes the behavior of an object. In the script, methods like calculating the total price or printing an invoice are mentioned, showing how they contribute to the functionality of a class.

💡Interface

An interface in programming defines a contract for methods that must be implemented by a class. The script discusses interfaces in the context of the Dependency Inversion Principle, emphasizing the importance of depending on abstractions rather than concrete classes.

💡Abstraction

Abstraction is a concept where you focus on the essential characteristics of an object or a class, ignoring the irrelevant details. The script touches on this concept when it talks about high-level modules depending on abstractions, which is part of the Dependency Inversion Principle.

Highlights

Introduction to the SOLID principles, which are fundamental to object-oriented design and should be well-known to developers.

Explanation of the Single Responsibility Principle, emphasizing that a class should have only one reason to change.

The importance of reducing duplicate code and the benefits it brings to maintainability and flexibility in software development.

Discussion on how the principles help in reducing complexity and making the software more understandable and flexible.

An example of applying the Single Responsibility Principle in a class design, illustrating how it simplifies the class's purpose.

The concept of Open/Closed Principle, stating that software entities should be open for extension but closed for modification.

How to apply the Open/Closed Principle to allow for extending the functionality without modifying the existing code.

Liskov Substitution Principle and its role in ensuring that derived classes can replace their base classes without affecting the correctness of the program.

The importance of creating flexible and reusable code by following the Liskov Substitution Principle.

Explanation of the Interface Segregation Principle, highlighting the need for creating narrow, client-specific interfaces.

How to avoid implementing unnecessary functions in a class by adhering to the Interface Segregation Principle.

Dependency Inversion Principle and its significance in depending on abstractions, not on concretions.

The benefits of the Dependency Inversion Principle in making the system more modular and easier to extend.

Practical examples of how the SOLID principles can be applied in real-world software development scenarios.

The impact of SOLID principles on code readability, maintainability, and the ease of adding new features to a system.

Discussion on the challenges faced when applying the SOLID principles and how to overcome them for better software design.

The role of SOLID principles in promoting good coding practices and their importance in professional software development.

Encouragement for developers to share and discuss their experiences with the SOLID principles to foster better coding practices.