Properties

Part of the Object Oriented Programming section of Coddy's GDScript journey. Lesson 6 of 65.

The variables a class declares are its properties (also called member variables): the data every object carries. Declare them at the top of the class, each with a type and a starting value:

# player.gd
class_name Player
extends RefCounted

var player_name: String = "Hero"
var level: int = 1
var hp: float = 100.0
var inventory: Array[String] = []

A property declared without a value starts at the default of its type: 0 for int, "" for String, false for bool and an empty array for Array[String].

Outside the class you read and change a property with a dot. Inside the class's methods you use its name:

var p := Player.new()
p.level += 1
p.inventory.append("sword")
print(p.level) # 2
print(p.inventory) # ["sword"]

Every object gets its own copy of each property, arrays included: the [] creates a new empty array for each player, so another player's inventory stays empty.

The type is checked: p.level = "max" is an error reported before the program runs, because level holds an int.

Challenge

Easy

Complete the class Player in player.gd. Declare these properties:

player_name, a String that starts as "Hero"
level, an int that starts at 1
hp, an int that starts at 100
inventory, an Array[String] that starts empty

Then complete the method describe(). It returns NAME (level LEVEL, HP hp): ITEMS, where ITEMS is the inventory joined with ", ", or no items when the inventory is empty.

The supplied code reads a name for one player, then how many commands follow, then the commands: hit AMOUNT, item NAME or level. It changes the player's properties directly and finally prints describe() for that player and for a second player it never changed. For Ada and the commands hit 30, item sword, level and item shield it prints:

Ada (level 2, 70 hp): sword, shield
Hero (level 1, 100 hp): no items

Your code goes in player.gd. main.gd holds the supplied input/output code and cannot be edited.

Try it yourself

extends Node

func _ready():
	# Supplied input/output code: keep it as it is
	var hero := Player.new()
	hero.player_name = OS.read_string_from_stdin()
	var guest := Player.new()
	var count := int(OS.read_string_from_stdin())
	for i in count:
		var parts := OS.read_string_from_stdin().split(" ")
		match parts[0]:
			"hit":
				hero.hp -= int(parts[1])
			"item":
				hero.inventory.append(parts[1])
			"level":
				hero.level += 1
	print(hero.describe())
	print(guest.describe())

Test yourself

This lesson includes a short quiz. Start the lesson to answer it and track your progress.

All lessons in Object Oriented Programming

3Inheritance

Basic Inheritance The super Keyword Method Overriding Inheritance Chains Type Checks with is Recap - Employee Hierarchy

6Special Methods

Virtual Methods Introduction The _to_string Method Custom Iterators Recap - Custom List

9Design Patterns Part 1

Intro to Design Patterns Singleton Pattern Factory Pattern Observer Pattern Strategy Pattern

12Final Challenges

E-learning Platform Banking System Game Character Development Vehicle Rental Service

Practice on your own: Online GDScript compiler