Acronym. Design principles. Object-oriented paradigm.
Aim: maintainability, reusable, scale, flexibility.
The principles are a subset of many principles promoted by American software engineer and instructor Robert C. Martin. Implementing them can help create more maintainable, scalable, and robust systems. Apply them judiciously; too rigid and they over-complicate. They are guidelines, not laws.
Single Responsibility Principle (SRP)
A class should have a single responsibility — one "reason to change". Divide at class level.
Example: File (read, write) versus a FileRead class and a FileWrite class.
A class should have only one job. If a class assumes multiple responsibilities, it becomes more difficult to maintain and understand.
Open/Closed Principle (OCP)
Open for extension but closed for modification.
Software entities (classes, modules, functions, etc.) should be open for extension but closed for modification. The behavior of a module can be extended without modifying its source code. Typically this is achieved using interfaces or abstract classes.
Liskov Substitution Principle (LSP)
Objects in a program should be replaceable with instances of their subtypes without altering the correctness of that program. This extends OCP to subclassing: a subclass can stand in for its parent class without any issues.
Interface Segregation Principle (ISP)
No client should be forced to depend on methods it does not use. Interfaces should be specific to the client that uses them, rather than one general-purpose interface. This reduces the side effects of changes and avoids clients implementing methods they don't need.
Dependency Inversion Principle (DIP)
High-level modules should not depend on low-level modules. Both should depend on abstractions. Additionally, abstractions should not depend on details; details should depend on abstractions. This reduces the direct dependency between high-level and low-level modules.
