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

Summary

The 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.