somebody was once making some objects and noticed they all had something in common so they made some kind of parent object that these objects could “inherit” from — they are really vague definitions, in Vulcan you can see a lot of classes inherit from a base class

Example of Inheritance

Notice all the child classes get all the "shapes" of its parent class -- in programming that would be similar to reusing properties and methods of the base class

Two types of inheritance

Classical Inheritance

Prototypal Inheritance

- Inheriting from a parent class 

- Inheritance is made at compile time

example: inheritance in java, C#

- Inheriting from an instance of the class: an object

- Inheritance is made on the fly/ dynamically meaning that you are really going back to the super class for those properties, saves on memory

example: Javascript

Example of Inheritance: Animal Kingdom

Animal

Fish

Birds

Mammals

Dogs

People

Example of Inheritance: Animal Kingdom

Animal

Fish

Birds

Mammals

Dogs

People

Platypus

??

Example of Inheritance: Animal Kingdom

Fish

Birds

Mammals

Dogs

People

Platypus

??

with inheritance this can be a problem because if some subclass doesn't fit entirely into the superclasses: what can you do ?

What can you do?

Two options:

1. redefine the class above it, mammals that lay eggs and mammals that give live birth

2. override the method of gives_birth() within that platypus subclass only

recommendations when using inheritance:

1. make sure it passes the IS-A vs. HAS-A test
2. keep the inheritance hierarchy shallow
3. use POCOs — plain old class objects, without methods on them,  just properties (eg: using properties that will always be relevant like first name and last name for a class Person()
   • now we are able to pass this Animal() to a controller who acts on the Animal() and saves the changes — example of using composition with Inheritance

Using Composition

- this is another way to get reusability out of other classes

- not a hierarchy structure

- each composition class can be very specific 

Managing the Complexity — best practice is to use a combination of the two

A TacoTruck() with multiple roles/responsibilities:

- have a TacoTruck class with a property on it called roles: [list]

- have a Role class with a shallow inheritance structure for when another class has more than one role 

- have a property on TacoTruck class called roles

- have a Role class with a shallow inheritance that can be combined into a composiition structure when a class like TacoTruck() has  more than one role