SOLID Principles

These are one of the oldest guidelines of system design. But they are very much applicable even today

1 The Single Reusability Principle

• It states that a group of functions in a module/ file should have only one reason to change.
• Restating, Code that changes together lives together.
• Make the software system follow the hierarchy of the organization not allow them

2 The Open-Closed Principle

• Make software systems easy to be changed by ability to allow changes by adding new code over changing existing code.
• Create a new class by extending a class over adding more functions to the existing class

3 The Liskov Substitution Principle

• A software should be designed using interchangeable parts (Plugin architecture) And the interchangeable parts need to be follow rules specific to that plugin.
• In terms of OOPs All interchangeable classes need to implement the same interface.
• Due to this, the classes that are dependent on these interchangeable classes will always have the data/ methods that they depend on.

4 ISP: The Interface Segregation Principle

• Do not depend on the things that you do not use.
• If it is necessary add interfaces between such relationships which will invert the dependency.

5 Dependency inversion principle

• Don’t refer to volatile concrete classes
• Don’t derive from volatile concrete classes.
• Don’t override concrete functions
• If any of these is necessary to be done create an interface and use it as an agreement which both need to always follow