The Flaws of Inheritance

Step-by-Step Tutorial: Understanding Composition Over Inheritance

1. Understanding Inheritance and Composition:

• Inheritance: Inheritance is when a class contains functionality that you want to reuse, and you create a subclass to extend this functionality.
• Composition: Composition is an alternative to inheritance where classes simply use the code they need without inheriting from a parent class.

2. Example of Inheritance:

• In the provided example, there is an Image class representing an RGB image with methods like resize, flip horizontally/vertically, save, and load.
• Subclasses like JpgImage, PngImage, and BmpImage inherit from the Image class to implement their versions of load and save methods.

3. Issues with Inheritance:

• Inheritance can lead to issues when changes are needed in the code structure.
• Changes in the parent class can break existing functionality in child classes, leading to maintenance challenges.

4. Introduction to Composition:

• Composition is a design approach where classes are composed of other classes or objects, rather than inheriting from a parent class.
• It allows for more flexibility and avoids the pitfalls of inheritance.

5. Implementing Composition:

• Instead of inheriting from a parent class, classes are composed of the necessary objects.
• Methods in the classes no longer access parent class methods directly but receive the required objects as parameters.

6. Using Interfaces for Abstraction:

• Interfaces define a contract specifying the methods that classes implementing the interface must provide.
• Interfaces allow for abstraction without the constraints of inheritance.

7. Benefits of Interfaces:

• Interfaces provide a lightweight way to define contracts between classes.
• They allow for flexibility in implementing methods without the rigid structure of inheritance.

8. Dependency Injection for Flexibility:

• Dependency Injection is a design pattern where objects are passed into a class rather than created within it.
• It allows for greater flexibility and testability in the codebase.

9. Applying Composition in Your Code:

• When designing classes, consider using composition over inheritance for better code maintainability and flexibility.
• Use interfaces to define contracts between classes and reduce dependencies on inheritance.

10. Best Practices for Design:

• Avoid deep inheritance hierarchies and opt for composition where possible.
• Use interfaces to define clear contracts between classes and promote code flexibility.

By following these steps and understanding the concepts of composition over inheritance, you can design more flexible and maintainable code structures in your projects.