The document discusses the open closed principle of object-oriented programming and design, which states that software entities like classes should be open for extension but closed for modification. This means that once a class is complete, its implementation can only be modified to fix errors, and new features require creating a new class rather than changing the existing one. An example is given to illustrate how applying the principle avoids issues that can arise from modifying existing classes, like breaking single responsibility, tests, APIs, and applications.

1. Open Closed Principle

2. ●
OOP and OOD
●
Open Closed Principle
●
The Idea
●
Problems Solved
●
Example and Discussion

3. Object Oriented Programming

4. Object-oriented programming (OOP) is a
programming paradigm that represents
concepts as "objects" that have data fields
(attributes that describe the object) and
associated procedures known as methods.

5. Object Oriented Design

6. Object-oriented design is the process of
planning a system of interacting objects for the
purpose of solving a software problem.

7. Open Closed Principle

8. "software entities (classes, modules,
functions, etc.) should be open for extension,
but closed for modification"

9. The idea was that once completed, the
implementation of a class could only be
modified to correct errors; new or changed
features would require that a different class be
created.

10. Class keeps growing when requirements are
increased, which is to add new functionalities
to it.

11. Break single responsibility at some point

12. Break existing test and public API

13. Break application

14. Example

15. Discussion

16. When to know if a class is completed?

17. When to know that we are applying OCP?

18. What do I do if business logic has changed?