.. _doc_gdscript: GDScript ======== Introduction ------------ *GDScript* is a high level, dynamically typed programming language used to create content. It uses a syntax similar to `Python `_ (blocks are indent-based and many keywords are similar). Its goal is to be optimized for and tightly integrated with Godot Engine, allowing great flexibility for content creation and integration. History ~~~~~~~ In the early days, the engine used the `Lua `__ scripting language. Lua is fast, but creating bindings to an object oriented system (by using fallbacks) was complex and slow and took an enormous amount of code. After some experiments with `Python `__, it also proved difficult to embed. The last third party scripting language that was used for shipped games was `Squirrel `__, but it was dropped as well. At that point, it became evident that a custom scripting language could more optimally make use of Godot's particular architecture: - Godot embeds scripts in nodes. Most languages are not designed with this in mind. - Godot uses several built-in data types for 2D and 3D math. Script languages do not provide this, and binding them is inefficient. - Godot uses threads heavily for lifting and initializing data from the net or disk. Script interpreters for common languages are not friendly to this. - Godot already has a memory management model for resources, most script languages provide their own, which results in duplicate effort and bugs. - Binding code is always messy and results in several failure points, unexpected bugs and generally low maintainability. The result of these considerations is *GDScript*. The language and interpreter for GDScript ended up being smaller than the binding code itself for Lua and Squirrel, while having equal functionality. With time, having a built-in language has proven to be a huge advantage. Example of GDScript ~~~~~~~~~~~~~~~~~~~ Some people can learn better by taking a look at the syntax, so here's a simple example of how GDScript looks. :: # A file is a class! # Inheritance extends BaseClass # (optional) class definition with a custom icon class_name MyClass, "res://path/to/optional/icon.svg" # Member Variables var a = 5 var s = "Hello" var arr = [1, 2, 3] var dict = {"key": "value", 2:3} var typed_var: int var inferred_type := "String" # Constants const ANSWER = 42 const THE_NAME = "Charly" # Enums enum {UNIT_NEUTRAL, UNIT_ENEMY, UNIT_ALLY} enum Named {THING_1, THING_2, ANOTHER_THING = -1} # Built-in Vector Types var v2 = Vector2(1, 2) var v3 = Vector3(1, 2, 3) # Function func some_function(param1, param2): var local_var = 5 if param1 < local_var: print(param1) elif param2 > 5: print(param2) else: print("Fail!") for i in range(20): print(i) while param2 != 0: param2 -= 1 var local_var2 = param1 + 3 return local_var2 # Functions override functions with the same name on the base/parent class. # If you still want to call them, use '.' (like 'super' in other languages). func something(p1, p2): .something(p1, p2) # Inner Class class Something: var a = 10 # Constructor func _init(): print("Constructed!") var lv = Something.new() print(lv.a) If you have previous experience with statically typed languages such as C, C++, or C# but never used a dynamically typed one before, it is advised you read this tutorial: :ref:`doc_gdscript_more_efficiently`. Language -------- In the following, an overview is given to GDScript. Details, such as which methods are available to arrays or other objects, should be looked up in the linked class descriptions. Identifiers ~~~~~~~~~~~ Any string that restricts itself to alphabetic characters (``a`` to ``z`` and ``A`` to ``Z``), digits (``0`` to ``9``) and ``_`` qualifies as an identifier. Additionally, identifiers must not begin with a digit. Identifiers are case-sensitive (``foo`` is different from ``FOO``). Keywords ~~~~~~~~ The following is the list of keywords supported by the language. Since keywords are reserved words (tokens), they can't be used as identifiers. Operators (like ``in``, ``not``, ``and`` or ``or``) and names of built-in types as listed in the following sections are also reserved. Keywords are defined in the `GDScript tokenizer `_ in case you want to take a look under the hood. +------------+---------------------------------------------------------------------------------------------------------------+ | Keyword | Description | +============+===============================================================================================================+ | if | See `if/else/elif`_. | +------------+---------------------------------------------------------------------------------------------------------------+ | elif | See `if/else/elif`_. | +------------+---------------------------------------------------------------------------------------------------------------+ | else | See `if/else/elif`_. | +------------+---------------------------------------------------------------------------------------------------------------+ | for | See for_. | +------------+---------------------------------------------------------------------------------------------------------------+ | do | Reserved for future implementation of do...while loops. | +------------+---------------------------------------------------------------------------------------------------------------+ | while | See while_. | +------------+---------------------------------------------------------------------------------------------------------------+ | match | See match_. | +------------+---------------------------------------------------------------------------------------------------------------+ | switch | Reserved for future implementation. | +------------+---------------------------------------------------------------------------------------------------------------+ | case | Reserved for future implementation. | +------------+---------------------------------------------------------------------------------------------------------------+ | break | Exits the execution of the current ``for`` or ``while`` loop. | +------------+---------------------------------------------------------------------------------------------------------------+ | continue | Immediately skips to the next iteration of the ``for`` or ``while`` loop. | +------------+---------------------------------------------------------------------------------------------------------------+ | pass | Used where a statement is required syntactically but execution of code is undesired, e.g. in empty functions. | +------------+---------------------------------------------------------------------------------------------------------------+ | return | Returns a value from a function. | +------------+---------------------------------------------------------------------------------------------------------------+ | class | Defines a class. | +------------+---------------------------------------------------------------------------------------------------------------+ | extends | Defines what class to extend with the current class. | +------------+---------------------------------------------------------------------------------------------------------------+ | is | Tests whether a variable extends a given class, or is of a given built-in type. | +------------+---------------------------------------------------------------------------------------------------------------+ | as | Cast the value to a given type if possible. | +------------+---------------------------------------------------------------------------------------------------------------+ | self | Refers to current class instance. | +------------+---------------------------------------------------------------------------------------------------------------+ | tool | Executes the script in the editor. | +------------+---------------------------------------------------------------------------------------------------------------+ | signal | Defines a signal. | +------------+---------------------------------------------------------------------------------------------------------------+ | func | Defines a function. | +------------+---------------------------------------------------------------------------------------------------------------+ | static | Defines a static function. Static member variables are not allowed. | +------------+---------------------------------------------------------------------------------------------------------------+ | const | Defines a constant. | +------------+---------------------------------------------------------------------------------------------------------------+ | enum | Defines an enum. | +------------+---------------------------------------------------------------------------------------------------------------+ | var | Defines a variable. | +------------+---------------------------------------------------------------------------------------------------------------+ | onready | Initializes a variable once the Node the script is attached to and its children are part of the scene tree. | +------------+---------------------------------------------------------------------------------------------------------------+ | export | Saves a variable along with the resource it's attached to and makes it visible and modifiable in the editor. | +------------+---------------------------------------------------------------------------------------------------------------+ | setget | Defines setter and getter functions for a variable. | +------------+---------------------------------------------------------------------------------------------------------------+ | breakpoint | Editor helper for debugger breakpoints. | +------------+---------------------------------------------------------------------------------------------------------------+ | preload | Preloads a class or variable. See `Classes as resources`_. | +------------+---------------------------------------------------------------------------------------------------------------+ | yield | Coroutine support. See `Coroutines with yield`_. | +------------+---------------------------------------------------------------------------------------------------------------+ | assert | Asserts a condition, logs error on failure. Ignored in non-debug builds. See `Assert keyword`_. | +------------+---------------------------------------------------------------------------------------------------------------+ | remote | Networking RPC annotation. See :ref:`high-level multiplayer docs `. | +------------+---------------------------------------------------------------------------------------------------------------+ | master | Networking RPC annotation. See :ref:`high-level multiplayer docs `. | +------------+---------------------------------------------------------------------------------------------------------------+ | puppet | Networking RPC annotation. See :ref:`high-level multiplayer docs `. | +------------+---------------------------------------------------------------------------------------------------------------+ | remotesync | Networking RPC annotation. See :ref:`high-level multiplayer docs `. | +------------+---------------------------------------------------------------------------------------------------------------+ | mastersync | Networking RPC annotation. See :ref:`high-level multiplayer docs `. | +------------+---------------------------------------------------------------------------------------------------------------+ | puppetsync | Networking RPC annotation. See :ref:`high-level multiplayer docs `. | +------------+---------------------------------------------------------------------------------------------------------------+ | PI | PI constant. | +------------+---------------------------------------------------------------------------------------------------------------+ | TAU | TAU constant. | +------------+---------------------------------------------------------------------------------------------------------------+ | INF | Infinity constant. Used for comparisons. | +------------+---------------------------------------------------------------------------------------------------------------+ | NAN | NAN (not a number) constant. Used for comparisons. | +------------+---------------------------------------------------------------------------------------------------------------+ Operators ~~~~~~~~~ The following is the list of supported operators and their precedence. +---------------------------------------------------------------+-----------------------------------------+ | **Operator** | **Description** | +---------------------------------------------------------------+-----------------------------------------+ | ``x[index]`` | Subscription, Highest Priority | +---------------------------------------------------------------+-----------------------------------------+ | ``x.attribute`` | Attribute Reference | +---------------------------------------------------------------+-----------------------------------------+ | ``is`` | Instance Type Checker | +---------------------------------------------------------------+-----------------------------------------+ | ``~`` | Bitwise NOT | +---------------------------------------------------------------+-----------------------------------------+ | ``-x`` | Negative / Unary Negation | +---------------------------------------------------------------+-----------------------------------------+ | ``*`` ``/`` ``%`` | Multiplication / Division / Remainder | | | | | | These operators have the same behavior | | | as C++. Integer division is truncated | | | rather than returning a fractional | | | number, and the % operator is only | | | available for ints ("fmod" for floats) | +---------------------------------------------------------------+-----------------------------------------+ | ``+`` | Addition / Concatenation of Arrays | +---------------------------------------------------------------+-----------------------------------------+ | ``-`` | Subtraction | +---------------------------------------------------------------+-----------------------------------------+ | ``<<`` ``>>`` | Bit Shifting | +---------------------------------------------------------------+-----------------------------------------+ | ``&`` | Bitwise AND | +---------------------------------------------------------------+-----------------------------------------+ | ``^`` | Bitwise XOR | +---------------------------------------------------------------+-----------------------------------------+ | ``|`` | Bitwise OR | +---------------------------------------------------------------+-----------------------------------------+ | ``<`` ``>`` ``==`` ``!=`` ``>=`` ``<=`` | Comparisons | +---------------------------------------------------------------+-----------------------------------------+ | ``in`` | Content Test | +---------------------------------------------------------------+-----------------------------------------+ | ``!`` ``not`` | Boolean NOT | +---------------------------------------------------------------+-----------------------------------------+ | ``and`` ``&&`` | Boolean AND | +---------------------------------------------------------------+-----------------------------------------+ | ``or`` ``||`` | Boolean OR | +---------------------------------------------------------------+-----------------------------------------+ | ``if x else`` | Ternary if/else | +---------------------------------------------------------------+-----------------------------------------+ | ``=`` ``+=`` ``-=`` ``*=`` ``/=`` ``%=`` ``&=`` ``|=`` | Assignment, Lowest Priority | +---------------------------------------------------------------+-----------------------------------------+ Literals ~~~~~~~~ +--------------------------+----------------------------------------+ | **Literal** | **Type** | +--------------------------+----------------------------------------+ | ``45`` | Base 10 integer | +--------------------------+----------------------------------------+ | ``0x8F51`` | Base 16 (hex) integer | +--------------------------+----------------------------------------+ | ``3.14``, ``58.1e-10`` | Floating point number (real) | +--------------------------+----------------------------------------+ | ``"Hello"``, ``"Hi"`` | Strings | +--------------------------+----------------------------------------+ | ``"""Hello"""`` | Multiline string | +--------------------------+----------------------------------------+ | ``@"Node/Label"`` | NodePath or StringName | +--------------------------+----------------------------------------+ | ``$NodePath`` | Shorthand for ``get_node("NodePath")`` | +--------------------------+----------------------------------------+ Comments ~~~~~~~~ Anything from a ``#`` to the end of the line is ignored and is considered a comment. :: # This is a comment. Multi-line comments can be created using """ (three quotes in a row) at the beginning and end of a block of text. Note that this creates a string, therefore, it will not be stripped away when the script is compiled. :: """ Everything on these lines is considered a comment. """ Built-in types -------------- Built-in types are stack-allocated. They are passed as values. This means a copy is created on each assignment or when passing them as arguments to functions. The only exceptions are ``Array``\ s and ``Dictionaries``, which are passed by reference so they are shared. (Not ``PoolArray``\ s like ``PoolByteArray`` though, those are passed as values too, so consider this when deciding which to use!) Basic built-in types ~~~~~~~~~~~~~~~~~~~~ A variable in GDScript can be assigned to several built-in types. null ^^^^ ``null`` is an empty data type that contains no information and can not be assigned any other value. bool ^^^^ The Boolean data type can only contain ``true`` or ``false``. int ^^^ The integer data type can only contain integer numbers, (both negative and positive). float ^^^^^ Used to contain a floating point value (real numbers). :ref:`String ` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ A sequence of characters in `Unicode format `_. Strings can contain the `standard C escape sequences `_. GDScript supports :ref:`format strings aka printf functionality `. Vector built-in types ~~~~~~~~~~~~~~~~~~~~~ :ref:`Vector2 ` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 2D vector type containing ``x`` and ``y`` fields. Can also be accessed as array. :ref:`Rect2 ` ^^^^^^^^^^^^^^^^^^^^^^^^^^ 2D Rectangle type containing two vectors fields: ``position`` and ``size``. Alternatively contains an ``end`` field which is ``position+size``. :ref:`Vector3 ` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 3D vector type containing ``x``, ``y`` and ``z`` fields. This can also be accessed as an array. :ref:`Transform2D ` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 3x2 matrix used for 2D transforms. :ref:`Plane ` ^^^^^^^^^^^^^^^^^^^^^^^^^^ 3D Plane type in normalized form that contains a ``normal`` vector field and a ``d`` scalar distance. :ref:`Quat ` ^^^^^^^^^^^^^^^^^^^^^^^^ Quaternion is a datatype used for representing a 3D rotation. It's useful for interpolating rotations. :ref:`AABB ` ^^^^^^^^^^^^^^^^^^^^^^^^ Axis-aligned bounding box (or 3D box) contains 2 vectors fields: ``position`` and ``size``. Alternatively contains an ``end`` field which is ``position+size``. :ref:`Basis ` ^^^^^^^^^^^^^^^^^^^^^^^^^^ 3x3 matrix used for 3D rotation and scale. It contains 3 vector fields (``x``, ``y`` and ``z``) and can also be accessed as an array of 3D vectors. :ref:`Transform ` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ 3D Transform contains a Basis field ``basis`` and a Vector3 field ``origin``. Engine built-in types ~~~~~~~~~~~~~~~~~~~~~ :ref:`Color ` ^^^^^^^^^^^^^^^^^^^^^^^^^^ Color data type contains ``r``, ``g``, ``b``, and ``a`` fields. It can also be accessed as ``h``, ``s``, and ``v`` for hue/saturation/value. :ref:`NodePath ` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Compiled path to a node used mainly in the scene system. It can be easily assigned to, and from, a String. :ref:`RID ` ^^^^^^^^^^^^^^^^^^^^^^ Resource ID (RID). Servers use generic RIDs to reference opaque data. :ref:`Object ` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Base class for anything that is not a built-in type. Container built-in types ~~~~~~~~~~~~~~~~~~~~~~~~ :ref:`Array ` ^^^^^^^^^^^^^^^^^^^^^^^^^^ Generic sequence of arbitrary object types, including other arrays or dictionaries (see below). The array can resize dynamically. Arrays are indexed starting from index ``0``. Starting with Godot 2.1, indices may be negative like in Python, to count from the end. :: var arr = [] arr = [1, 2, 3] var b = arr[1] # This is 2. var c = arr[arr.size() - 1] # This is 3. var d = arr[-1] # Same as the previous line, but shorter. arr[0] = "Hi!" # Replacing value 1 with "Hi!". arr.append(4) # Array is now ["Hi!", 2, 3, 4]. GDScript arrays are allocated linearly in memory for speed. Large arrays (more than tens of thousands of elements) may however cause memory fragmentation. If this is a concern special types of arrays are available. These only accept a single data type. They avoid memory fragmentation and also use less memory but are atomic and tend to run slower than generic arrays. They are therefore only recommended to use for large data sets: - :ref:`PoolByteArray `: An array of bytes (integers from 0 to 255). - :ref:`PoolIntArray `: An array of integers. - :ref:`PoolRealArray `: An array of floats. - :ref:`PoolStringArray `: An array of strings. - :ref:`PoolVector2Array `: An array of :ref:`Vector2 ` objects. - :ref:`PoolVector3Array `: An array of :ref:`Vector3 ` objects. - :ref:`PoolColorArray `: An array of :ref:`Color ` objects. :ref:`Dictionary ` ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Associative container which contains values referenced by unique keys. :: var d = {4: 5, "A key": "A value", 28: [1, 2, 3]} d["Hi!"] = 0 d = { 22: "value", "some_key": 2, "other_key": [2, 3, 4], "more_key": "Hello" } Lua-style table syntax is also supported. Lua-style uses ``=`` instead of ``:`` and doesn't use quotes to mark string keys (making for slightly less to write). Note however that like any GDScript identifier, keys written in this form cannot start with a digit. :: var d = { test22 = "value", some_key = 2, other_key = [2, 3, 4], more_key = "Hello" } To add a key to an existing dictionary, access it like an existing key and assign to it:: var d = {} # Create an empty Dictionary. d.waiting = 14 # Add String "Waiting" as a key and assign the value 14 to it. d[4] = "hello" # Add integer 4 as a key and assign the String "hello" as its value. d["Godot"] = 3.01 # Add String "Godot" as a key and assign the value 3.01 to it. Data ---- Variables ~~~~~~~~~ Variables can exist as class members or local to functions. They are created with the ``var`` keyword and may, optionally, be assigned a value upon initialization. :: var a # Data type is 'null' by default. var b = 5 var c = 3.8 var d = b + c # Variables are always initialized in order. Variables can optionally have a type specification. When a type is specified, the variable will be forced to have always that same type, and trying to assign an incompatible value will raise an error. Types are specified in the variable declaration using a ``:`` (colon) symbol after the variable name, followed by the type. :: var my_vector2: Vector2 var my_node: Node = Sprite.new() If the variable is initialized within the declaration the type can be inferred, so it's possible to omit the type name:: var my_vector2 := Vector2() # 'my_vector2' is of type 'Vector2' var my_node := Sprite.new() # 'my_node' is of type 'Sprite' Type inference is only possible if the assigned value has a defined type, otherwise it will raise an error. Valid types are: - Built-in types (Array, Vector2, int, String, etc.) - Engine classes (Node, Resource, Reference, etc.) - Constant names if they contain a script resource (``MyScript`` if you declared ``const MyScript = preload("res://my_script.gd")``). - Other classes in the same script, respecting scope (``InnerClass.NestedClass`` if you declared ``class NestedClass`` inside the ``class InnerClass`` in the same scope) - Script classes declared with the ``class_name`` keyword. Casting ^^^^^^^ Values assigned to typed variables must have a compatible type. If it's needed to coerce a value to be of a certain type, in particular for object types, you can use the casting operator ``as``. Casting between object types results on the same object if the value is of the same type or a subtype of the casted type. :: var my_node2D: Node2D my_node2D = $Sprite as Node2D # Works since Sprite is subtype of Node2D If the value is not a subtype, the casting operation will result in a ``null`` value. :: var my_node2D: Node2D my_node2D = $Button # Results in 'null' since a Button is not a subtype of Node2D For built-in types, they will be forcibly converted if possible, otherwise the engine will raise an error. :: var my_int: int my_int = "123" as int # The string can be converted to int my_int = Vector2() as int # A Vector2 can't be converted to int, this will cause an error Casting is also useful to have better type-safe variables when interacting with tree:: # will infer the variable to be of type Sprite: var my_sprite := $Character as Sprite # will fail if $AnimPlayer is not an AnimationPlayer, even if it has the method 'play()': ($AnimPlayer as AnimationPlayer).play("walk") Constants ~~~~~~~~~ Constants are similar to variables, but must be constants or constant expressions and must be assigned on initialization. :: const A = 5 const B = Vector2(20, 20) const C = 10 + 20 # Constant expression. const D = Vector2(20, 30).x # Constant expression: 20 const E = [1, 2, 3, 4][0] # Constant expression: 1 const F = sin(20) # sin() can be used in constant expressions. const G = x + 20 # Invalid; this is not a constant expression! Although the type of constants are inferred from the assigned value, it's also possible to add explicit type specification:: const A: int = 5 const B: Vector2 = Vector2() Assigning a value of an incompatible type will raise an error. Enums ^^^^^ Enums are basically a shorthand for constants, and are pretty useful if you want to assign consecutive integers to some constant. If you pass a name to the enum, it would also put all the values inside a constant dictionary of that name. :: enum {TILE_BRICK, TILE_FLOOR, TILE_SPIKE, TILE_TELEPORT} # Is the same as: const TILE_BRICK = 0 const TILE_FLOOR = 1 const TILE_SPIKE = 2 const TILE_TELEPORT = 3 enum State {STATE_IDLE, STATE_JUMP = 5, STATE_SHOOT} # Is the same as: const STATE_IDLE = 0 const STATE_JUMP = 5 const STATE_SHOOT = 6 const State = {STATE_IDLE = 0, STATE_JUMP = 5, STATE_SHOOT = 6} Functions ~~~~~~~~~ Functions always belong to a `class `_. The scope priority for variable look-up is: local → class member → global. The ``self`` variable is always available and is provided as an option for accessing class members, but is not always required (and should *not* be sent as the function's first argument, unlike Python). :: func my_function(a, b): print(a) print(b) return a + b # Return is optional; without it 'null' is returned. A function can ``return`` at any point. The default return value is ``null``. Functions can also have type specification for the arguments and for the return value. Types for arguments can be added in a similar way to variables:: func my_function(a: int, b: String): pass If a function argument has a default value, it's possible to infer the type:: func my_function(int_arg := 42, String_arg := "string"): pass The return type of the function can be specified after the arguments list using the arrow token (``->``):: func my_int_function() -> int: return 0 Functions that have a return type **must** return a proper value. Setting the type as ``void`` means the function doesn't return anything. Void functions can return early with the ``return`` keyword, but they can't return any value. :: void_function() -> void: return # Can't return a value .. note:: Non-void functions must **always** return a value, so if your code have branching statements (such as ``if``/``else`` construct), all the possible paths must have a return. E.g., if you have a ``return`` inside an ``if`` block but not after it, the editor will raise an error because if the block is not executed the function won't have a valid value to return. Referencing Functions ^^^^^^^^^^^^^^^^^^^^^ Contrary to Python, functions are *not* first class objects in GDScript. This means they cannot be stored in variables, passed as an argument to another function or be returned from other functions. This is for performance reasons. To reference a function by name at runtime, (e.g. to store it in a variable, or pass it to another function as an argument) one must use the ``call`` or ``funcref`` helpers:: # Call a function by name in one step. my_node.call("my_function", args) # Store a function reference. var my_func = funcref(my_node, "my_function") # Call stored function reference. my_func.call_func(args) Remember that default functions like ``_init``, and most notifications such as ``_enter_tree``, ``_exit_tree``, ``_process``, ``_physics_process``, etc. are called in all base classes automatically. So there is only a need to call the function explicitly when overloading them in some way. Static functions ^^^^^^^^^^^^^^^^ A function can be declared static. When a function is static it has no access to the instance member variables or ``self``. This is mainly useful to make libraries of helper functions: :: static func sum2(a, b): return a + b Statements and control flow ~~~~~~~~~~~~~~~~~~~~~~~~~~~ Statements are standard and can be assignments, function calls, control flow structures, etc (see below). ``;`` as a statement separator is entirely optional. if/else/elif ^^^^^^^^^^^^ Simple conditions are created by using the ``if``/``else``/``elif`` syntax. Parenthesis around conditions are allowed, but not required. Given the nature of the tab-based indentation, ``elif`` can be used instead of ``else``/``if`` to maintain a level of indentation. :: if [expression]: statement(s) elif [expression]: statement(s) else: statement(s) Short statements can be written on the same line as the condition:: if 1 + 1 == 2: return 2 + 2 else: var x = 3 + 3 return x Sometimes you might want to assign a different initial value based on a boolean expression. In this case ternary-if expressions come in handy:: var x = [value] if [expression] else [value] y += 3 if y < 10 else -1 while ^^^^^ Simple loops are created by using ``while`` syntax. Loops can be broken using ``break`` or continued using ``continue``: :: while [expression]: statement(s) for ^^^ To iterate through a range, such as an array or table, a *for* loop is used. When iterating over an array, the current array element is stored in the loop variable. When iterating over a dictionary, the *index* is stored in the loop variable. :: for x in [5, 7, 11]: statement # Loop iterates 3 times with 'x' as 5, then 7 and finally 11. var dict = {"a": 0, "b": 1, "c": 2} for i in dict: print(dict[i]) for i in range(3): statement # Similar to [0, 1, 2] but does not allocate an array. for i in range(1,3): statement # Similar to [1, 2] but does not allocate an array. for i in range(2,8,2): statement # Similar to [2, 4, 6] but does not allocate an array. for c in "Hello": print(c) # Iterate through all characters in a String, print every letter on new line. match ^^^^^ A ``match`` statement is used to branch execution of a program. It's the equivalent of the ``switch`` statement found in many other languages but offers some additional features. Basic syntax: :: match [expression]: [pattern](s): [block] [pattern](s): [block] [pattern](s): [block] **Crash-course for people who are familiar to switch statements**: 1. Replace ``switch`` with ``match`` 2. Remove ``case`` 3. Remove any ``break``'s. If you don't want to ``break`` by default you can use ``continue`` for a fallthrough. 4. Change ``default`` to a single underscore. **Control flow**: The patterns are matched from top to bottom. If a pattern matches, the corresponding block will be executed. After that, the execution continues below the ``match`` statement. If you want to have a fallthrough you can use ``continue`` to stop execution in the current block and check the ones below it. There are 6 pattern types: - constant pattern constant primitives, like numbers and strings :: match x: 1: print("We are number one!") 2: print("Two are better than one!") "test": print("Oh snap! It's a string!") - variable pattern matches the contents of a variable/enum :: match typeof(x): TYPE_FLOAT: print("float") TYPE_STRING: print("text") TYPE_ARRAY: print("array") - wildcard pattern This pattern matches everything. It's written as a single underscore. It can be used as the equivalent of the ``default`` in a ``switch`` statement in other languages. :: match x: 1: print("It's one!") 2: print("It's one times two!") _: print("It's not 1 or 2. I don't care tbh.") - binding pattern A binding pattern introduces a new variable. Like the wildcard pattern, it matches everything - and also gives that value a name. It's especially useful in array and dictionary patterns. :: match x: 1: print("It's one!") 2: print("It's one times two!") var new_var: print("It's not 1 or 2, it's ", new_var) - array pattern matches an array. Every single element of the array pattern is a pattern itself so you can nest them. The length of the array is tested first, it has to be the same size as the pattern, otherwise the pattern don't match. **Open-ended array**: An array can be bigger than the pattern by making the last subpattern ``..`` Every subpattern has to be comma separated. :: match x: []: print("Empty array") [1, 3, "test", null]: print("Very specific array") [var start, _, "test"]: print("First element is ", start, ", and the last is \"test\"") [42, ..]: print("Open ended array") - dictionary pattern Works in the same way as the array pattern. Every key has to be a constant pattern. The size of the dictionary is tested first, it has to be the same size as the pattern, otherwise the pattern don't match. **Open-ended dictionary**: A dictionary can be bigger than the pattern by making the last subpattern ``..`` Every subpattern has to be comma separated. If you don't specify a value, then only the existence of the key is checked. A value pattern is separated from the key pattern with a ``:`` :: match x: {}: print("Empty dict") {"name": "Dennis"}: print("The name is Dennis") {"name": "Dennis", "age": var age}: print("Dennis is ", age, " years old.") {"name", "age"}: print("Has a name and an age, but it's not Dennis :(") {"key": "godotisawesome", ..}: print("I only checked for one entry and ignored the rest") Multipatterns: You can also specify multiple patterns separated by a comma. These patterns aren't allowed to have any bindings in them. :: match x: 1, 2, 3: print("It's 1 - 3") "Sword", "Splash potion", "Fist": print("Yep, you've taken damage") Classes ~~~~~~~ By default, all script files are unnamed classes. In this case, you can only reference them using the file's path, using either a relative or an absolute path. For example, if you name a script file ``character.gd`` :: # Inherit from Character.gd extends res://path/to/character.gd # Load character.gd and create a new node instance from it var Character = load("res://path/to/character.gd") var character_node = Character.new() Instead, you can give your class a name to register it as a new type in Godot's editor. For that, you use the 'class_name' keyword. You can add an optional comma followed by a path to an image, to use it as an icon. Your class will then appear with its new icon in the editor: :: # Item.gd extends Node class_name Item, "res://interface/icons/item.png" .. image:: img/class_name_editor_register_example.png Here's a class file example: :: # Saved as a file named 'character.gd'. class_name Character var health = 5 func print_health(): print(health) func print_this_script_three_times(): print(get_script()) print(ResourceLoader.load("res://character.gd")) print(Character) .. note:: Godot's class syntax is compact: it can only contain member variables or functions. You can use static functions, but not static member variables. In the same way, the engine initializes variables every time you create an instance, and this includes arrays and dictionaries. This is in the spirit of thread safety, since scripts can be initialized in separate threads without the user knowing. Inheritance ^^^^^^^^^^^ A class (stored as a file) can inherit from - A global class - Another class file - An inner class inside another class file. Multiple inheritance is not allowed. Inheritance uses the ``extends`` keyword: :: # Inherit/extend a globally available class. extends SomeClass # Inherit/extend a named class file. extends "somefile.gd" # Inherit/extend an inner class in another file. extends "somefile.gd".SomeInnerClass To check if a given instance inherits from a given class the ``is`` keyword can be used: :: # Cache the enemy class. const Enemy = preload("enemy.gd") # [...] # Use 'is' to check inheritance. if (entity is Enemy): entity.apply_damage() To call a function in a *base class* (i.e. one ``extend``-ed in your current class), prepend ``.`` to the function name: :: .basefunc(args) This is especially useful because functions in extending classes replace functions with the same name in their base classes. So if you still want to call them, you can use ``.`` like the ``super`` keyword in other languages: :: func some_func(x): .some_func(x) # Calls same function on the parent class. Class Constructor ^^^^^^^^^^^^^^^^^ The class constructor, called on class instantiation, is named ``_init``. As mentioned earlier, the constructors of parent classes are called automatically when inheriting a class. So there is usually no need to call ``._init()`` explicitly. Unlike the call of a regular function like in the above example with ``.some_func``, if the constructor from the inherited class takes arguments, they are passed like this: :: func _init(args).(parent_args): pass This is better explained through examples. Say we have this scenario: :: # State.gd (inherited class) var entity = null var message = null func _init(e=null): entity = e func enter(m): message = m # Idle.gd (inheriting class) extends "State.gd" func _init(e=null, m=null).(e): # Do something with 'e'. message = m There are a few things to keep in mind here: 1. if the inherited class (``State.gd``) defines a ``_init`` constructor that takes arguments (``e`` in this case) then the inheriting class (``Idle.gd``) *has* to define ``_init`` as well and pass appropriate parameters to ``_init`` from ``State.gd`` 2. ``Idle.gd`` can have a different number of arguments than the base class ``State.gd`` 3. in the example above ``e`` passed to the ``State.gd`` constructor is the same ``e`` passed in to ``Idle.gd`` 4. if ``Idle.gd``'s ``_init`` constructor takes 0 arguments it still needs to pass some value to the ``State.gd`` base class even if it does nothing. Which brings us to the fact that you can pass literals in the base constructor as well, not just variables. Eg.: :: # Idle.gd func _init().(5): pass Inner classes ^^^^^^^^^^^^^ A class file can contain inner classes. Inner classes are defined using the ``class`` keyword. They are instanced using the ``ClassName.new()`` function. :: # Inside a class file. # An inner class in this class file. class SomeInnerClass: var a = 5 func print_value_of_a(): print(a) # This is the constructor of the class file's main class. func _init(): var c = SomeInnerClass.new() c.print_value_of_a() Classes as resources ^^^^^^^^^^^^^^^^^^^^ Classes stored as files are treated as :ref:`resources `. They must be loaded from disk to access them in other classes. This is done using either the ``load`` or ``preload`` functions (see below). Instancing of a loaded class resource is done by calling the ``new`` function on the class object:: # Load the class resource when calling load(). var my_class = load("myclass.gd") # Preload the class only once at compile time. const MyClass = preload("myclass.gd") func _init(): var a = MyClass.new() a.some_function() Exports ~~~~~~~ Class members can be exported. This means their value gets saved along with the resource (e.g. the :ref:`scene `) they're attached to. They will also be available for editing in the property editor. Exporting is done by using the ``export`` keyword:: extends Button export var number = 5 # Value will be saved and visible in the property editor. An exported variable must be initialized to a constant expression or have an export hint in the form of an argument to the export keyword (see below). One of the fundamental benefits of exporting member variables is to have them visible and editable in the editor. This way artists and game designers can modify values that later influence how the program runs. For this, a special export syntax is provided. :: # If the exported value assigns a constant or constant expression, # the type will be inferred and used in the editor. export var number = 5 # Export can take a basic data type as an argument which will be # used in the editor. export(int) var number # Export can also take a resource type to use as a hint. export(Texture) var character_face export(PackedScene) var scene_file # Integers and strings hint enumerated values. # Editor will enumerate as 0, 1 and 2. export(int, "Warrior", "Magician", "Thief") var character_class # Editor will enumerate with string names. export(String, "Rebecca", "Mary", "Leah") var character_name # Named Enum Values # Editor will enumerate as THING_1, THING_2, ANOTHER_THING. enum NamedEnum {THING_1, THING_2, ANOTHER_THING = -1} export (NamedEnum) var x # Strings as Paths # String is a path to a file. export(String, FILE) var f # String is a path to a directory. export(String, DIR) var f # String is a path to a file, custom filter provided as hint. export(String, FILE, "*.txt") var f # Using paths in the global filesystem is also possible, # but only in tool scripts (see further below). # String is a path to a PNG file in the global filesystem. export(String, FILE, GLOBAL, "*.png") var tool_image # String is a path to a directory in the global filesystem. export(String, DIR, GLOBAL) var tool_dir # The MULTILINE setting tells the editor to show a large input # field for editing over multiple lines. export(String, MULTILINE) var text # Limiting editor input ranges # Allow integer values from 0 to 20. export(int, 20) var i # Allow integer values from -10 to 20. export(int, -10, 20) var j # Allow floats from -10 to 20, with a step of 0.2. export(float, -10, 20, 0.2) var k # Allow values y = exp(x) where y varies between 100 and 1000 # while snapping to steps of 20. The editor will present a # slider for easily editing the value. export(float, EXP, 100, 1000, 20) var l # Floats with Easing Hint # Display a visual representation of the ease() function # when editing. export(float, EASE) var transition_speed # Colors # Color given as Red-Green-Blue value export(Color, RGB) var col # Color is RGB. # Color given as Red-Green-Blue-Alpha value export(Color, RGBA) var col # Color is RGBA. # Another node in the scene can be exported too. export(NodePath) var node It must be noted that even if the script is not being run while at the editor, the exported properties are still editable (see below for "tool"). Exporting bit flags ^^^^^^^^^^^^^^^^^^^ Integers used as bit flags can store multiple ``true``/``false`` (boolean) values in one property. By using the export hint ``int, FLAGS``, they can be set from the editor: :: # Individually edit the bits of an integer. export(int, FLAGS) var spell_elements = ELEMENT_WIND | ELEMENT_WATER Restricting the flags to a certain number of named flags is also possible. The syntax is similar to the enumeration syntax: :: # Set any of the given flags from the editor. export(int, FLAGS, "Fire", "Water", "Earth", "Wind") var spell_elements = 0 In this example, ``Fire`` has value 1, ``Water`` has value 2, ``Earth`` has value 4 and ``Wind`` corresponds to value 8. Usually, constants should be defined accordingly (e.g. ``const ELEMENT_WIND = 8`` and so on). Using bit flags requires some understanding of bitwise operations. If in doubt, boolean variables should be exported instead. Exporting arrays ^^^^^^^^^^^^^^^^ Exporting arrays works but with an important caveat: While regular arrays are created local to every class instance, exported arrays are *shared* between all instances. This means that editing them in one instance will cause them to change in all other instances. Exported arrays can have initializers, but they must be constant expressions. :: # Exported array, shared between all instances. # Default value must be a constant expression. export var a = [1, 2, 3] # Exported arrays can specify type (using the same hints as before). export(Array, int) var ints = [1,2,3] export(Array, int, "Red", "Green", "Blue") var enums = [2, 1, 0] export(Array, Array, float) var two_dimensional = [[1, 2], [3, 4]] # You can omit the default value, but then it would be null if not assigned. export(Array) var b export(Array, PackedScene) var scenes # Typed arrays also work, only initialized empty: export var vector3s = PoolVector3Array() export var strings = PoolStringArray() # Regular array, created local for every instance. # Default value can include run-time values, but can't # be exported. var c = [a, 2, 3] Setters/getters ~~~~~~~~~~~~~~~ It is often useful to know when a class' member variable changes for whatever reason. It may also be desired to encapsulate its access in some way. For this, GDScript provides a *setter/getter* syntax using the ``setget`` keyword. It is used directly after a variable definition: :: var variable = value setget setterfunc, getterfunc Whenever the value of ``variable`` is modified by an *external* source (i.e. not from local usage in the class), the *setter* function (``setterfunc`` above) will be called. This happens *before* the value is changed. The *setter* must decide what to do with the new value. Vice-versa, when ``variable`` is accessed, the *getter* function (``getterfunc`` above) must ``return`` the desired value. Below is an example: :: var myvar setget my_var_set, my_var_get func my_var_set(new_value): my_var = new_value func my_var_get(): return my_var # Getter must return a value. Either of the *setter* or *getter* functions can be omitted: :: # Only a setter. var my_var = 5 setget myvar_set # Only a getter (note the comma). var my_var = 5 setget ,myvar_get Get/Setters are especially useful when exporting variables to editor in tool scripts or plugins, for validating input. As said *local* access will *not* trigger the setter and getter. Here is an illustration of this: :: func _init(): # Does not trigger setter/getter. my_integer = 5 print(my_integer) # Does trigger setter/getter. self.my_integer = 5 print(self.my_integer) Tool mode ~~~~~~~~~ Scripts, by default, don't run inside the editor and only the exported properties can be changed. In some cases it is desired that they do run inside the editor (as long as they don't execute game code or manually avoid doing so). For this, the ``tool`` keyword exists and must be placed at the top of the file: :: tool extends Button func _ready(): print("Hello") Memory management ~~~~~~~~~~~~~~~~~ If a class inherits from :ref:`class_Reference`, then instances will be freed when no longer in use. No garbage collector exists, just reference counting. By default, all classes that don't define inheritance extend **Reference**. If this is not desired, then a class must inherit :ref:`class_Object` manually and must call instance.free(). To avoid reference cycles that can't be freed, a ``weakref`` function is provided for creating weak references. Alternatively, when not using references, the ``is_instance_valid(instance)`` can be used to check if an object has been freed. Signals ~~~~~~~ It is often desired to send a notification that something happened in an instance. GDScript supports creation of built-in Godot signals. Declaring a signal in GDScript is easy using the `signal` keyword. :: # No arguments. signal your_signal_name # With arguments. signal your_signal_name_with_args(a, b) These signals can be connected in the editor or from code like regular signals. Take the instance of a class where the signal was declared and connect it to the method of another instance: :: func _callback_no_args(): print("Got callback!") func _callback_args(a,b): print("Got callback with args! a: ", a, " and b: ", b) func _at_some_func(): instance.connect("your_signal_name", self, "_callback_no_args") instance.connect("your_signal_name_with_args", self, "_callback_args") It is also possible to bind arguments to a signal that lacks them with your custom values: :: func _at_some_func(): instance.connect("your_signal_name", self, "_callback_args", [22, "hello"]) This is useful when a signal from many objects is connected to a single callback and the sender must be identified: :: func _button_pressed(which): print("Button was pressed: ", which.get_name()) func _ready(): for b in get_node("buttons").get_children(): b.connect("pressed", self, "_button_pressed",[b]) Finally, emitting a custom signal is done by using the Object.emit_signal method: :: func _at_some_func(): emit_signal("your_signal_name") emit_signal("your_signal_name_with_args", 55, 128) some_instance.emit_signal("some_signal") Coroutines with yield ~~~~~~~~~~~~~~~~~~~~~ GDScript offers support for `coroutines `_ via the ``yield`` built-in function. Calling ``yield()`` will immediately return from the current function, with the current frozen state of the same function as the return value. Calling ``resume`` on this resulting object will continue execution and return whatever the function returns. Once resumed the state object becomes invalid. Here is an example: :: func my_func(): print("Hello") yield() print("world") func _ready(): var y = my_func() # Function state saved in 'y'. print("my dear") y.resume() # 'y' resumed and is now an invalid state. Will print: :: Hello my dear world It is also possible to pass values between yield() and resume(), for example: :: func my_func(): print("Hello") print(yield()) return "cheers!" func _ready(): var y = my_func() # Function state saved in 'y'. print(y.resume("world")) # 'y' resumed and is now an invalid state. Will print: :: Hello world cheers! Coroutines & signals ^^^^^^^^^^^^^^^^^^^^ The real strength of using ``yield`` is when combined with signals. ``yield`` can accept two parameters, an object and a signal. When the signal is received, execution will recommence. Here are some examples: :: # Resume execution the next frame. yield(get_tree(), "idle_frame") # Resume execution when animation is done playing. yield(get_node("AnimationPlayer"), "finished") # Wait 5 seconds, then resume execution. yield(get_tree().create_timer(5.0), "timeout") Coroutines themselves use the ``completed`` signal when they transition into an invalid state, for example: :: func my_func(): yield(button_func(), "completed") print("All buttons were pressed, hurray!") func button_func(): yield($Button0, "pressed") yield($Button1, "pressed") ``my_func`` will only continue execution once both the buttons are pressed. Onready keyword ~~~~~~~~~~~~~~~ When using nodes, it's common to desire to keep references to parts of the scene in a variable. As scenes are only warranted to be configured when entering the active scene tree, the sub-nodes can only be obtained when a call to Node._ready() is made. :: var my_label func _ready(): my_label = get_node("MyLabel") This can get a little cumbersome, especially when nodes and external references pile up. For this, GDScript has the ``onready`` keyword, that defers initialization of a member variable until _ready is called. It can replace the above code with a single line: :: onready var my_label = get_node("MyLabel") Assert keyword ~~~~~~~~~~~~~~ The ``assert`` keyword can be used to check conditions in debug builds. These assertions are ignored in non-debug builds. :: # Check that 'i' is 0. assert(i == 0)