Introduction to Design Principles
Object-oriented design principles are fundamental concepts and guidelines used in software development process to create well structured, scalable and maintainable code using object oriented programming languages like Java, C++, Python, and others. These principles help software designers and developers build systems that are easy to understand, extend, and modify. Here is an introduction to some of the key object oriented design principles:
- Encapsulation is the concept of bundling data (attributes) and methods (functions) that operate on that data into a single unit called a class. This helps hide the internal details of a class from external code and provides a clear interface for interacting with the object.
- Inheritance is a mechanism that allows one class (subclass or derived class) to inherit properties and behaviors (attributes and methods) from another class (superclass or base class). It promotes code reuse and the creation of specialized classes.
- Abstraction is the process of simplifying complex systems by breaking them down into smaller, more manageable parts. In OOP, this is achieved through classes and objects. It allows developers to focus on essential characteristics of an object while hiding irrelevant details.
- Polymorphism means the ability of objects to take on multiple forms. In OOP, this is achieved through method overriding and method overloading. It allows different classes to implement the same method in a way that is specific to their individual needs.
Single Responsibility Principle (SRP)
- SRP states that a class should have only one reason to change. In other words, a class should have a single responsibility or job. This principle promotes code modularity and makes classes easier to maintain.
Open/Closed Principle (OCP)
- OCP suggests that a class should be open for extension but closed for modification. This means that you can add new functionality to a class without altering its existing code. Achieving this often involves using interfaces, abstract classes, and design patterns like the Strategy Pattern.
Liskov Substitution Principle (LSP)
- LSP states that objects of a derived class should be able to replace objects of the base class without affecting the correctness of the program. In other words, subclasses should be true extensions of their parent classes, preserving the same interface.
Interface Segregation Principle (ISP)
- ISP advises that clients should not be forced to depend on interfaces they do not use. It encourages the creation of specific, smaller interfaces tailored to the needs of the clients, rather than one large, monolithic interface.
Dependency Inversion Principle (DIP)
- DIP advocates that high-level modules should not depend on low-level modules. Both should depend on abstractions (interfaces or abstract classes). It promotes loose coupling and makes the system more flexible and maintainable.
Composition Over Inheritance
- This principle suggests that it is often better to use composition (combining smaller objects) rather than relying solely on inheritance for code reuse. Composition can lead to more flexible and maintainable code.
Don’t Repeat Yourself (DRY)
- DRY encourages developers to avoid duplicating code by promoting code reuse. When code is duplicated, it becomes harder to maintain and update, and increases the risk of bugs.
Law of Demeter (LoD) or Principle of Least Knowledge
- LoD states that an object should only interact with its immediate neighbors, meaning it should not have knowledge of the internal structure of other objects. This reduces dependencies and improves system stability.
By following these object oriented design principles, software developers can create well-organized, modular, and adaptable code that is easier to understand and maintain, ultimately leading to more robust and efficient software systems. These principles are not strict rules but rather guidelines that help developers make informed design decisions based on the principles of OOP.