Open-Closed Principle         

Quickstart Guide         

SOLID

“ Software entities (classes, modules, functions, etc.) should be open for extension, but closed for modification. “

https://en.wikipedia.org/wiki/Open%E2%80%93closed_principle

Add new functionality without changing the existing code

What do we aim for ?

No need to disturb its clients

Dependency

Flow of Control

“Protect Controller from changes of Presenter”

For example, we should ...

Concept

Meyer's open/closed principle

Inheritance

Problem：Tight Coupling

the subclasses depend on implementation details of their parent class.

Meyer's open/closed principle

Inheritance

Example 1-1

Overriding...

Multiple Inheritance...

Concept

Robert C. Martin's open/closed principle

 Polymorphic

Interface

allow different implementations which you can easily substitute without changing the code that uses them.

Robert C. Martin's open/closed principle

 Polymorphic

“Composition over inheritance”

Robert C. Martin's open/closed principle

 Polymorphic

Example 2-1

Consider it ....

Robert C. Martin's open/closed principle

 Polymorphic

Example 2-1

Consider it ....

! Keyword Class shouldn't consider the implementation detail of file/api reader.

Change the implementation detail of reader will influence Keyword

! File/Api reader can't be reused.

It may violate DRY in future

Robert C. Martin's open/closed principle

 Polymorphic

Example 2-2

Make accountability clear