[inheritance] 상속 with 예제

 

In OOP languages, classes can extend existing classes to inherit their behavior. At the same time, they can changeand extendthe behavior.

 

*reminder : A class is an abstraction and represents a consistent combination of state(instance variables or “fields”) and operations to alter this state (“methods”).

 

Lets start with the class represents "Animal" which has age and food state, and next_day, feed, is_alive, make_noise methods

there is a unified diagram to represent class : unified modeling language (UML)

Now, let's create concrete animal classes (cat, dog) that inherit above Animal class

OOP languages support Polymorphism so make_noise is dynamically “dispatched”.

It can be decided at the runtime of a program, depending on the type of the receiver object, which implementation of a specific method needs to be invoked.

But It does not make sense to instantiate Animal, how can we prevent it? 

=> abstraction base class!

 

 

An abstract base class can provide functionality that is relevant for subclasses without being constructable(cannot be instantiated). Define abstract methods in an abstract base class to indicate that subclasses must implement a particular method (template methods).

 

Private : __food is only visible from within the class and subclasses 

Protected : _hunger is only visible from within the class and subclasses in the same module - in Python only by convention! 

Public : make_noise is visible to any other class

 

 

 

Let’s Implement Kangaroos ! it has baby in pouch