| language | contributors | filename | |||
|---|---|---|---|---|---|
GDScript |
|
learngdscript.gd |
GDScript is a dynamically typed scripting language made specifically for free and open source game engine Godot. GDScript's syntax is similar to Python's. Its main advantages are ease of use and tight integration with the engine. It's a perfect fit for game development.
# Single-line comments are written using hash symbol.
"""
Multi-line
comments
are
written
using
docstrings.
"""
# Script file is a class in itself and you can optionally define a name for it.
class_name MyClass
# Inheritance
extends Node2D
# Member variables
var x = 8 # int
var y = 1.2 # float
var b = true # bool
var s = "Hello World!" # String
var a = [1, false, "brown fox"] # Array - similar to list in Python,
# it can hold different types
# of variables at once.
var d = {
"key" : "value",
42 : true
} # Dictionary holds key-value pairs.
var p_arr = PoolStringArray(["Hi", "there", "!"]) # Pool arrays can
# only hold a certain type.
# Built-in vector types:
var v2 = Vector2(1, 2)
var v3 = Vector3(1, 2, 3)
# Constants
const ANSWER_TO_EVERYTHING = 42
const BREAKFAST = "Spam and eggs!"
# Enums
enum { ZERO, ONE , TWO, THREE }
enum NamedEnum { ONE = 1, TWO, THREE }
# Exported variables are visible in the inspector.
export(int) var age
export(float) var height
export var person_name = "Bob" # Export type hints are unnecessary
# if you set a default value.
# Functions
func foo():
pass # pass keyword is a placeholder for future code
func add(first, second):
return first + second
# Printing values
func printing():
print("GDScript ", "is ", " awesome.")
prints("These", "words", "are", "divided", "by", "spaces.")
printt("These", "words", "are", "divided", "by", "tabs.")
printraw("This gets printed to system console.")
# Math
func doing_math():
var first = 8
var second = 4
print(first + second) # 12
print(first - second) # 4
print(first * second) # 32
print(first / second) # 2
print(first % second) # 0
# There are also +=, -=, *=, /=, %= etc.,
# however no ++ or -- operators.
print(pow(first, 2)) # 64
print(sqrt(second)) # 2
printt(PI, TAU, INF, NAN) # built-in constants
# Control flow
func control_flow():
x = 8
y = 2 # y was originally a float,
# but we can change its type to int
# using the power of dynamic typing!
if x < y:
print("x is smaller than y")
elif x > y:
print("x is bigger than y")
else:
print("x and y are equal")
var a = true
var b = false
var c = false
if a and b or not c: # alternatively you can use &&, || and !
print("This is true!")
for i in range(20): # GDScript's range is similar to Python's
print(i) # so this will print numbers from 0 to 19
for i in 20: # unlike Python, you can loop over an int directly
print(i) # so this will also print numbers from 0 to 19
for i in ["two", 3, 1.0]: # iterating over an array
print(i)
while x > y:
printt(x, y)
y += 1
x = 2
y = 10
while x < y:
x += 1
if x == 6:
continue # 6 won't get printed because of continue statement
prints("x is equal to:", x)
if x == 7:
break # loop will break on 7, so 8, 9 and 10 won't get printed
match x:
1:
print("Match is similar to switch.")
2:
print("However you don't need to put cases before each value.")
3:
print("Furthermore each case breaks on default.")
break # ERROR! Break statement is unnecessary!
4:
print("If you need fallthrough use continue.")
continue
_:
print("Underscore is a default case.")
# ternary operator (one line if-else statement)
prints("x is", "positive" if x >= 0 else "negative")
# Casting
func casting_examples():
var i = 42
var f = float(42) # cast using variables constructor
var b = i as bool # or using "as" keyword
# Override functions
# By a convention built-in overridable functions start with an underscore,
# but in practice you can override virtually any function.
# _init is called when object gets initialized
# This is the object's constructor.
func _init():
# Initialize object's internal stuff here.
pass
# _ready gets called when script's node and
# its children have entered the scene tree.
func _ready():
pass
# _process gets called on every frame.
func _process(delta):
# The delta argument passed to this function is a number of seconds,
# which passed between the last frame and the current one.
print("Delta time equals: ", delta)
# _physics_process gets called on every physics frame.
# That means delta should be constant.
func _physics_process(delta):
# Simple movement using vector addition and multiplication.
var direction = Vector2(1, 0) # or Vector2.RIGHT
var speed = 100.0
self.global_position += direction * speed * delta
# self refers to current class instance
# When overriding you can call parent's function using the dot operator
# like here:
func get_children():
# Do some additional things here.
var r = .get_children() # call parent's implementation
return r
# Inner class
class InnerClass:
extends Object
func hello():
print("Hello from inner class!")
func use_inner_class():
var ic = InnerClass.new()
ic.hello()
ic.free() # use free for memory cleanupextends Node2D
var sprite # This variable will hold the reference.
# You can get references to other nodes in _ready.
func _ready() -> void:
# NodePath is useful for accessing nodes.
# Create NodePath by passing String to its constructor:
var path1 = NodePath("path/to/something")
# Or by using NodePath literal:
var path2 = @"path/to/something"
# NodePath examples:
var path3 = @"Sprite" # relative path, immediate child of the current node
var path4 = @"Timers/Firerate" # relative path, child of the child
var path5 = @".." # current node's parent
var path6 = @"../Enemy" # current node's sibling
var path7 = @"/root" # absolute path, equivalent to get_tree().get_root()
var path8 = @"/root/Main/Player/Sprite" # absolute path to Player's Sprite
var path9 = @"Timers/Firerate:wait_time" # accessing properties
var path10 = @"Player:position:x" # accessing subproperties
# Finally, to get a reference use one of these:
sprite = get_node(@"Sprite") as Sprite # always cast to the type you expect
sprite = get_node("Sprite") as Sprite # here String gets
# implicitly casted to NodePath
sprite = get_node(path3) as Sprite
sprite = get_node_or_null("Sprite") as Sprite
sprite = $Sprite as Sprite
func _process(delta):
# Now we can reuse the reference in other places.
prints("Sprite has global_position of", sprite.global_position)
# Use onready keyword to assign a value to
# a variable just before _ready executes.
# This is a commonly used syntax sugar.
onready var tween = $Tween as Tween
# You can export NodePath, so you can assign it within the inspector.
export var nodepath = @""
onready var reference = get_node(nodepath) as NodeSignal system is Godot's implementation of the observer programming pattern. Here's an example:
class_name Player extends Node2D
var hp = 10
signal died() # define signal
signal hurt(hp_old, hp_new) # signals can take arguments
func apply_damage(dmg):
var hp_old = hp
hp -= dmg
emit_signal("hurt", hp_old, hp) # emit signal and pass arguments
if hp <= 0:
emit_signal("died")
func _ready():
# connect signal "died" to function "_on_death" defined in self
self.connect("died", self, "_on_death")
func _on_death():
self.queue_free() # destroy Player on deathGDScript can optionally use static typing.
extends Node
var x: int # define typed variable
var y: float = 4.2
var z := 1.0 # infer type based on default value using := operator
onready var node_ref_typed := $Child as Node
export var speed := 50.0
const CONSTANT := "Typed constant."
func _ready() -> void:
# function returns nothing
x = "string" # ERROR! Type can't be changed!
return
func join(arg1: String, arg2: String) -> String:
# function takes two Strings and returns a String
return arg1 + arg2
func get_child_at(index: int) -> Node:
# function takes an int and returns a Node
return get_children()[index]
signal example(arg: int) # ERROR! Signals can't take typed arguments!