Programming for Game Design by Wallace Wang & Tonnetta Walcott

Author:Wallace Wang & Tonnetta Walcott
Language: eng
Format: epub
ISBN: 9798868801907
Publisher: Apress

Notice that the Plant class defines an x and y property along with an init() method that sets an initial value of 55 for x and 66 for y. Then the Car class inherits from the Plant class. Even though the Car class is completely empty (the “pass” command does nothing), the Car class inherits everything defined in the Plant class. That means the Car class inherits a value of 55 for its x property and a value of 66 for its y property.

The init() function creates a new object (ford) from the Car class. Then it prints the x and y properties of the ford object to show that it inherited the value of 55 for x and the value of 66 for y even though the Car class itself does nothing. The Car class simply copied everything in the Plant class.

Simply inheriting everything defined in one class isn’t useful since you might as well just use the class that defines everything. The more common use for inheritance is to extend (hence the keyword “extends”) a class by inheriting code from one class but adding new code as well.

Suppose you wanted to define a Car class with an x and y property to define a location but also a speed property to define how fast it’s going. A clumsy way would be to create a class that defines an x and y property like this:class Plant:

var x: int

var y: int

func _init():

x = 55

y = 66

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