Explain what is Composition over Inheritance?

Composition over inheritance is a principle in object-oriented programming that suggests favoring composition (combining objects or components) over inheritance (creating class hierarchies) to achieve code reuse, flexibility, and maintainability. It encourages the use of object composition as a more flexible alternative to inheritance for building complex systems.

Inheritance is a mechanism where a class inherits properties, methods, and behavior from a parent class. It establishes an “is-a” relationship between classes, creating a hierarchical structure. While inheritance can be useful in certain scenarios, it has some limitations:

  1. Rigid class hierarchies: Inheritance creates a fixed and often inflexible hierarchy of classes. Subclasses are tightly coupled to their parent class, limiting the flexibility to change or extend the behavior of individual classes.
  2. Code duplication and bloating: Inheritance can lead to code duplication and bloating when classes inherit irrelevant or unnecessary behavior from their parent classes. Inherited methods and attributes may not always be applicable or desired for a subclass, resulting in inefficient or cluttered code.
  3. Fragile base class problem: Inheritance can introduce fragility in the codebase. Modifying the base class can inadvertently affect its subclasses, potentially causing unintended consequences and requiring extensive testing and refactoring.

Composition, on the other hand, involves combining or assembling objects or components to create more complex behaviors or structures. Instead of relying on an “is-a” relationship, composition establishes a “has-a” relationship, where objects are composed of other objects to achieve their functionality.

Advantages of composition over inheritance include:

  1. Flexibility and modularity: Composition allows for greater flexibility and modularity in building systems. Objects can be composed or decomposed based on specific requirements, making it easier to modify or extend functionality without affecting the entire codebase.
  2. Code reuse: Composition promotes code reuse by combining existing components to create new objects or behaviors. Objects can be composed of multiple smaller, reusable components, resulting in more modular and reusable code.
  3. Separation of concerns: Composition allows for better separation of concerns by delegating specific responsibilities to individual objects or components. Each component can focus on its specific functionality, making the codebase more maintainable and easier to understand.
  4. Reduced coupling: Composition reduces the coupling between classes compared to inheritance. Objects are loosely coupled through interfaces or contracts, allowing for more flexibility in swapping or modifying components without affecting other parts of the system.

Overall, composition over inheritance promotes a more flexible, modular, and maintainable codebase by emphasizing the combination and reuse of smaller, specialized components. It allows for greater control and adaptability in building complex systems while avoiding the limitations and drawbacks associated with rigid class hierarchies.

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