#LyX 2.0 created this file. For more info see http://www.lyx.org/ \lyxformat 413 \begin_document \begin_header \textclass article \use_default_options true \maintain_unincluded_children false \language english \language_package default \inputencoding auto \fontencoding global \font_roman default \font_sans default \font_typewriter default \font_default_family default \use_non_tex_fonts false \font_sc false \font_osf false \font_sf_scale 100 \font_tt_scale 100 \graphics default \default_output_format default \output_sync 0 \bibtex_command default \index_command default \paperfontsize default \use_hyperref false \papersize default \use_geometry false \use_amsmath 1 \use_esint 1 \use_mhchem 1 \use_mathdots 1 \cite_engine basic \use_bibtopic false \use_indices false \paperorientation portrait \suppress_date false \use_refstyle 0 \index Index \shortcut idx \color #008000 \end_index \secnumdepth 3 \tocdepth 3 \paragraph_separation indent \paragraph_indentation default \quotes_language english \papercolumns 1 \papersides 1 \paperpagestyle default \tracking_changes false \output_changes false \html_math_output 0 \html_css_as_file 0 \html_be_strict false \end_header \begin_body \begin_layout Title GD Scripting Language (GDScript) \end_layout \begin_layout Section Introduction \end_layout \begin_layout Standard GDScript is a high level, dynamically typed programming language used to create content. It uses a syntax that is very similar to the Python language (blocks are indent-based) and it's goal is to be very optimal and tigthly integrated with the engine, allowing great flexibility for content creation and integratio n. \end_layout \begin_layout Section Example \end_layout \begin_layout Standard Some people can learn better by just taking a look at the syntax, so here's a simple example of how it looks. \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout #a file is a class! \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #inheritance \end_layout \begin_layout Plain Layout extends BaseClass \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #member variables \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout var a=5 \end_layout \begin_layout Plain Layout var s="Hello" \end_layout \begin_layout Plain Layout var arr=[1,2,3] \end_layout \begin_layout Plain Layout var dict={"key":"value", 2:3} \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #constants \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout const answer=42 \end_layout \begin_layout Plain Layout const thename="Charly" \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #built-in vector types \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout var v2 = Vector2(1,2) \end_layout \begin_layout Plain Layout var v3 = Vector3(1,2,3) \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #function \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout func some_function(param1,param2): \end_layout \begin_layout Plain Layout var local_var=5 \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout if param1 < local_var: \end_layout \begin_layout Plain Layout print(param1) \end_layout \begin_layout Plain Layout elif param2 > 5: \end_layout \begin_layout Plain Layout print(param2) \end_layout \begin_layout Plain Layout else: \end_layout \begin_layout Plain Layout print("fail!") \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout for i in range(20): \end_layout \begin_layout Plain Layout print(i) \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout while(param2!=0): \end_layout \begin_layout Plain Layout param2-=1 \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout var local_var2 = param1+3 \end_layout \begin_layout Plain Layout return local_var2 \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #subclass \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout class Something: \end_layout \begin_layout Plain Layout var a=10 \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #constructor \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout func _init(): \end_layout \begin_layout Plain Layout print("constructed!") \end_layout \begin_layout Plain Layout var lv = Something.new() \end_layout \begin_layout Plain Layout print(lv.a) \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout \end_layout \end_inset \end_layout \begin_layout Section Language \end_layout \begin_layout Subsection Identifiers \end_layout \begin_layout Standard Any string that restricts itself to alphabetic characters ('a' to 'z' and 'A' to 'Z'), digits ('0' to '9') and '_' qualifies as an identifier. As an extra restriction, identifiers must not begin with a digit. Identifiers are case-sensitive ('foo' is different to 'FOO'). \end_layout \begin_layout Subsection Keywords \end_layout \begin_layout Standard The following is the list of keywords supported by the language. Since keywords are reserved words (tokens), they can't be used as identifiers. \end_layout \begin_layout Subsection Operators \end_layout \begin_layout Standard The following is the list of supported operators and their precedence (TODO, change since this was made to reflect python operators) \end_layout \begin_layout Standard \begin_inset Tabular \begin_inset Text \begin_layout Plain Layout Operator \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Note \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout x[index] \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Subscription, Highest Priority \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout x.attribute \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Attribute Reference \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout extends \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Instance Type Checker \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout ~ \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Bitwise NOT \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout -x \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Negative \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout * / % \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Mult / Div / Remainder \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout + - \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Addition / Substraction \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout << >> \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Bit Shifting \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout & \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Bitwise AND \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout ^ \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Bitwise XOR \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout | \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Bitwise OR \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout < > == != >= <= \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Comparisons \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout in \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Content Test \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout ! not \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Boolean NOT \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout and && \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Boolean AND \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout or || \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Boolean OR \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout = += -= *= /= ^= &= |= \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Assignment, Lowest Priority \end_layout \end_inset \end_inset \end_layout \begin_layout Subsection Literals \end_layout \begin_layout Standard \begin_inset Tabular \begin_inset Text \begin_layout Plain Layout Literal \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Name \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 45 \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Base 10 Integer \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 0x8F51 \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Base 16 (hex) Integer \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 3.14, 58.1e-10 \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Floating Point Number (real) \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout 'Hello', \begin_inset Quotes eld \end_inset Hi \begin_inset Quotes erd \end_inset \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Strings \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout @'Hello', @'Hi' \end_layout \end_inset \begin_inset Text \begin_layout Plain Layout Internationalized Strings \end_layout \end_inset \end_inset \end_layout \begin_layout Subsection Comments \end_layout \begin_layout Standard Anything from a '#' to the end of the line is ignored and is considered a comment. \end_layout \begin_layout Standard \begin_inset listings lstparams "language=Python" inline false status open \begin_layout Plain Layout # This is a comment \end_layout \end_inset \end_layout \begin_layout Section Built-in Types \end_layout \begin_layout Subsection Basic Bult-In Types \end_layout \begin_layout Standard A variable in GDScript can be assigned many of several built-in types. \end_layout \begin_layout Subsubsection null \end_layout \begin_layout Standard 'null' is a data type that contains no information, nothing assigned, and it's just empy. It can only be set to one value: 'null'. \end_layout \begin_layout Subsubsection bool \end_layout \begin_layout Standard Boolean data type, can only contain 'true' or 'false'. \end_layout \begin_layout Subsubsection int \end_layout \begin_layout Standard Integer data type, can only contain integer numbers, negative and positive. \end_layout \begin_layout Subsubsection float \end_layout \begin_layout Standard contains a floating point value (real). \end_layout \begin_layout Subsubsection String \end_layout \begin_layout Standard Sequence of characters in unicode format. Strings can contain the standard C escape sequences. \end_layout \begin_layout Subsection Vector Built-In Types \end_layout \begin_layout Subsubsection Vector2/Size2 \end_layout \begin_layout Standard 2D vector type, containing x and y fields. Can alternatively access fields as width and height for readability. Can also be accessed as array. \end_layout \begin_layout Subsubsection Rect2 \end_layout \begin_layout Standard 2D Rectangle type. Contains 2 vectors fields, \begin_inset Quotes eld \end_inset pos \begin_inset Quotes erd \end_inset and size \begin_inset Quotes erd \end_inset . Alternatively contains an \begin_inset Quotes eld \end_inset end \begin_inset Quotes erd \end_inset field which is \begin_inset Quotes eld \end_inset pos+size \begin_inset Quotes erd \end_inset . \end_layout \begin_layout Subsubsection Vector3 \end_layout \begin_layout Standard 3D vector type. Contains x, y and z fields. Can also be accessed as array. \end_layout \begin_layout Subsubsection Matrix32 \end_layout \begin_layout Standard 3x2 matrix used for 2D transforms. \end_layout \begin_layout Subsubsection Plane \end_layout \begin_layout Standard 3D Plane type in normalized form. Contains a \begin_inset Quotes eld \end_inset normal \begin_inset Quotes erd \end_inset vector field and a \begin_inset Quotes eld \end_inset d \begin_inset Quotes erd \end_inset scalar distance. \end_layout \begin_layout Subsubsection Quat \end_layout \begin_layout Standard Quaternion, datatype used for representing a 3D rotation. It's useful for interpolating rotations. \end_layout \begin_layout Subsubsection AABB/Box3 \end_layout \begin_layout Standard Axis Aligned bounding box (or alternatively, 3D box). Contains 2 vectors fields, \begin_inset Quotes eld \end_inset pos \begin_inset Quotes erd \end_inset and size \begin_inset Quotes erd \end_inset . Alternatively contains an \begin_inset Quotes eld \end_inset end \begin_inset Quotes erd \end_inset field which is \begin_inset Quotes eld \end_inset pos+size \begin_inset Quotes erd \end_inset . \end_layout \begin_layout Subsubsection Matrix3 \end_layout \begin_layout Standard 3x3 matrix used for 3D rotation and scale. Contains 3 vector fields x,y and z. Can also be accessed as array of 3D vectors. \end_layout \begin_layout Subsubsection Transform \end_layout \begin_layout Standard 3D Transform, contains a Matrix3 field \begin_inset Quotes eld \end_inset basis \begin_inset Quotes erd \end_inset and a Vector3 field \begin_inset Quotes eld \end_inset origin \begin_inset Quotes erd \end_inset . \end_layout \begin_layout Subsection Engine Built-In Types \end_layout \begin_layout Subsubsection Color \end_layout \begin_layout Standard Color datatype, contains r,g,b,a fields. Can also be accessed as h,s,v for hue/saturation/value. \end_layout \begin_layout Subsubsection Image \end_layout \begin_layout Standard Contains a 2D Image of custom format and allows direct access to the pixels. \end_layout \begin_layout Subsubsection NodePath \end_layout \begin_layout Standard Compiled path to a node, used mainly in the scene system. Can be easily asigned from/to a String. \end_layout \begin_layout Subsubsection RID \end_layout \begin_layout Standard Resource ID (RID). Servers use generic RIDs to reference opaque data. \end_layout \begin_layout Subsubsection Object \end_layout \begin_layout Standard Base class for anything not a built-in type. \end_layout \begin_layout Subsubsection InputEvent \end_layout \begin_layout Standard Events from input devices are contained in very compact form in InputEvent objects. Due to fact they can be received in high amounts from frame to frame, they are optimized in their own datatype. \end_layout \begin_layout Subsection Container Built-In Types \end_layout \begin_layout Subsubsection Array \end_layout \begin_layout Standard Generic sequence of objects. It's size can be changed to anything and starts from index 0. \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout var arr=[] \end_layout \begin_layout Plain Layout arr=[1,2,3] \end_layout \begin_layout Plain Layout arr[0]="Hi!" \end_layout \end_inset \end_layout \begin_layout Standard Arrays are allocated linearly in memory, so they are fast, but very large arrays (more than tens of thousands of elements) may cause fragmentation. There are specialized arrays for some built-in datatypes which do not suffer from this and use much less memory. \end_layout \begin_layout Subsubsection Dictionary \end_layout \begin_layout Standard Associative container which contains values referenced by unique keys. \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout var dict={4:5, "a key":"a value", 28:[1,2,3]} \end_layout \begin_layout Plain Layout dict["Hi!"]=0 \end_layout \end_inset \end_layout \begin_layout Subsubsection ByteArray \end_layout \begin_layout Standard Array of bytes. Can only contains bytes (integers from 0 to 255). Optimized for memory usage, can't fragment the memory. \end_layout \begin_layout Subsubsection IntArray \end_layout \begin_layout Standard Array of integers. Can only contain integers. Optimized for memory usage, can't fragment the memory. \end_layout \begin_layout Subsubsection FloatArray \end_layout \begin_layout Standard Array of floats, can only contain floats. Optimized for memory usage, can't fragment the memory. \end_layout \begin_layout Subsubsection StringArray \end_layout \begin_layout Standard Array of strings, can only contain strings. Optimized for memory usage, can't fragment the memory. \end_layout \begin_layout Subsubsection Vector2Array \end_layout \begin_layout Standard Array of Vector2, can only contain 2D Vectors. Optimized for memory usage, can't fragment the memory. \end_layout \begin_layout Subsubsection Vector3Array \end_layout \begin_layout Standard Array of Vector3, can only contain 3D Vectors. Optimized for memory usage, can't fragment the memory. \end_layout \begin_layout Subsubsection ColorArray \end_layout \begin_layout Standard Array of Color, can only contains colors. Optimized for memory usage, can't fragment the memory. \end_layout \begin_layout Section Data \end_layout \begin_layout Subsection Variables \end_layout \begin_layout Standard Variables can exist as class members or local to functions. They are created with the \begin_inset Quotes eld \end_inset var \begin_inset Quotes erd \end_inset keyword and may be, optionally, be assigned a value upon initialization. \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout var a # datatype is null by default \end_layout \begin_layout Plain Layout var b = 5 \end_layout \begin_layout Plain Layout var c = 3.8 \end_layout \begin_layout Plain Layout var d = b+c # variables are always initialized in order \end_layout \end_inset \end_layout \begin_layout Subsection Constants \end_layout \begin_layout Standard Constants are similar to variables, but must be constants or constant expression s and must be assigned on initialization. \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout const a = 5 \end_layout \begin_layout Plain Layout const b = Vector2(20,20) \end_layout \begin_layout Plain Layout const c = 10+20 # constant expression \end_layout \begin_layout Plain Layout const d = Vector2(20,30).x # constant expression: 20 \end_layout \begin_layout Plain Layout const e = [1,2,3,4][0] # constant expression: 1 \end_layout \begin_layout Plain Layout const f = sin(20) # sin() can be used in constant expression \end_layout \begin_layout Plain Layout const g = x+20 # invalid, not a constant expression! \end_layout \begin_layout Plain Layout \end_layout \end_inset \end_layout \begin_layout Subsection Functions \end_layout \begin_layout Standard Functions always belong to a class. The scope priority for variable look-up is: local -> class member -> global. \begin_inset Quotes eld \end_inset self \begin_inset Quotes erd \end_inset is provided as an option for accessing class members but is not required always (and must \emph on not \emph default be defined as first parameter, like in Python). For performance reasons, functions are not considered class members, so they can't be referenced directly. A function can return at any point. The default return value is null. \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout func myfunction(a,b): \end_layout \begin_layout Plain Layout print(a) \end_layout \begin_layout Plain Layout print(b) \end_layout \begin_layout Plain Layout return a+b # return is optional, otherwise null is returned \end_layout \end_inset \end_layout \begin_layout Subsubsection Statements and Control Flow \end_layout \begin_layout Standard Statements are standard, and can be assignments, function calls, control flow structures, etc (see below). \begin_inset Quotes eld \end_inset ; \begin_inset Quotes erd \end_inset as separator is entirely optional. \end_layout \begin_layout Subsubsection if/else/elif \end_layout \begin_layout Standard Simple conditions are created by using the \emph on if/else/elif \emph default syntax. Parenthesis around statements is allowed but not requiered. Given the nature of the tab-based indentation, elif can be used instead of else:/if: to mantain a level of indentation. \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout if [expression]: \end_layout \begin_layout Plain Layout statement(s) \end_layout \begin_layout Plain Layout elif [expression]: \end_layout \begin_layout Plain Layout statement(s) \end_layout \begin_layout Plain Layout else: \end_layout \begin_layout Plain Layout statement(s) \end_layout \end_inset \end_layout \begin_layout Subsubsection while \end_layout \begin_layout Standard Simple loops are created by using \emph on while \emph default syntax. Loops can be broken using \emph on break \emph default , or continued using \emph on continue \emph default : \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout while [expression]: \end_layout \begin_layout Plain Layout statement(s) \end_layout \end_inset \end_layout \begin_layout Subsubsection for \end_layout \begin_layout Standard To iterate a range, array or table a \emph on for \emph default loop is used. For loops store the index in the loop variable on each iteration. \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout for i in [0,1,2]: \end_layout \begin_layout Plain Layout statement # loop iterates 3 times, i being 0,1 and 2 \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout var dict = {"a":0, "b":1, "c": 2} \end_layout \begin_layout Plain Layout for i in dict: \end_layout \begin_layout Plain Layout print(dict[i]) # loop iterates the keys, i being "a","b" and c". It prints 0, 1 and 2. \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout for i in range(3): \end_layout \begin_layout Plain Layout statement # similar to [0,1,2] but does not allocate an array \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout for i in range(1,3): \end_layout \begin_layout Plain Layout statement # similar to [1,2] but does not allocate an array \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout for i in range(2,8,2): \end_layout \begin_layout Plain Layout statement # similar to [2,4,6] but does not allocate an array \end_layout \begin_layout Plain Layout \end_layout \end_inset \end_layout \begin_layout Section Classes \end_layout \begin_layout Standard By default, the body of a script file is an unnamed class, and it can only be referenced externally as a resource or file. Class syntax is meant to be very compact and can only contain member variables or functions. Static functions are allowed, but not static members (in the spirit of thread safety, since scripts can be initialized in separate threads without the user knowing). In the same way, member variables (including arrays and dictionaries) are initialized every time an instance is created. \end_layout \begin_layout Subsection Class File Example \end_layout \begin_layout Standard Example of a class file, imagine it being stored in a file like myclass.gd. \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout \end_layout \begin_layout Plain Layout var a=5 \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout function print_value_of_a(): \end_layout \begin_layout Plain Layout print(a) \end_layout \begin_layout Plain Layout \end_layout \end_inset \end_layout \begin_layout Subsection Inheritance \end_layout \begin_layout Standard A class-file can inherit from a global class, another file or a subclass inside another file. Multiple inheritance is not allowed. The \begin_inset Quotes eld \end_inset extends \begin_inset Quotes erd \end_inset syntax is used: \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout # extend from some class (global) \end_layout \begin_layout Plain Layout extends SomeClass \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout # optionally, extend from another file \end_layout \begin_layout Plain Layout extends "somefile.gd" \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout # extend from a subclass in another file \end_layout \begin_layout Plain Layout extends "somefile.gd".Subclass \end_layout \end_inset \end_layout \begin_layout Subsection Inheritance Testing \end_layout \begin_layout Standard It is possible to check if an instance inherits from a given class. For this the \begin_inset Quotes eld \end_inset extends \begin_inset Quotes erd \end_inset keyword can be used as an operator instead: \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout static var enemy_class = preload("enemy.gd") # cache the enemy class \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout [..] \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout if ( entity extends enemy_class ): \end_layout \begin_layout Plain Layout entity.apply_damage() \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout \end_layout \end_inset \end_layout \begin_layout Subsection Constructor \end_layout \begin_layout Standard A class can have an optional constructor, a function named \begin_inset Quotes eld \end_inset _init \begin_inset Quotes erd \end_inset that is called when the class is instanced. \end_layout \begin_layout Subsection Sub Classes \end_layout \begin_layout Standard A class file can have subclasses. Syntax should be straightforward: \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout class SomeSubClass: \end_layout \begin_layout Plain Layout var a=5 \end_layout \begin_layout Plain Layout function print_value_of_a(): \end_layout \begin_layout Plain Layout print(a) \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout function _init(): \end_layout \begin_layout Plain Layout var sc = SomeSubClass.new() #instance by calling built-in new \end_layout \begin_layout Plain Layout sc.print_value_of_a() \end_layout \end_inset \end_layout \begin_layout Subsection Classes as Objects \end_layout \begin_layout Standard It may be desired at some point to load a class from a file and then instance it. Since the global scope does not exist, classes must be loaded as a resource. Instancing is done by calling the \begin_inset Quotes eld \end_inset new \begin_inset Quotes erd \end_inset function in a class object: \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout #load the class (loaded every time the script is instanced) \end_layout \begin_layout Plain Layout var MyClass = load("myclass.gd") \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #alternatively, using the preload() function preloads the class at compile time \end_layout \begin_layout Plain Layout var MyClass2 = preload("myclass.gd") \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout function _init(): \end_layout \begin_layout Plain Layout var a = MyClass.new() \end_layout \begin_layout Plain Layout a.somefunction() \end_layout \end_inset \end_layout \begin_layout Subsection Exports \end_layout \begin_layout Standard Class members can be exported. This means their value gets saved along with a scene. If class members have initializers to constant expressions, they will be available for editing in the property editor. Exporting is done by using the export keyword: \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout extends Button \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout export var data # value will be saved \end_layout \begin_layout Plain Layout export var number=5 # also available to the property editor \end_layout \begin_layout Plain Layout \end_layout \end_inset \end_layout \begin_layout Standard One of the fundamental benefits of exporting member variables is to have them visible in the property 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 for more detail in the exported variables: \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout #if the exported value assigns a constant or constant expression, the type will be infered and used in the editor \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout export var number=5 \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #export can take a basic datatype as argument, which will be used in the editor \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout export(int) var number \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #export can also take a resource type as hint \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout export(Texture) var character_face \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #integers and strings hint enumerated values \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout export(int,"Warrior","Magician","Thief") var character_class # (editor will set them as 0,1 and 2) \end_layout \begin_layout Plain Layout export(String,"Rebecca","Mary","Leah") var character_name \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #strings as paths \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout export(String,FILE) var f # string is a path to a file \end_layout \begin_layout Plain Layout export(String,DIR) var f # string is a path to a directory \end_layout \begin_layout Plain Layout export(String,FILE,"*.txt") var f # string is a path to a file, custom filter provided as hint \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #integers and floats hint ranges \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout export(int,20) var i # 0 to 20 allowed \end_layout \begin_layout Plain Layout export(int,-10,20) var j # -10 to 20 allowed \end_layout \begin_layout Plain Layout export(float,-10,20,0.2) var k # -10 to 20 allowed, with stepping of 0.2 \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout #color can hint availability of alpha \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout export(Color,RGB) var col # Color is RGB \end_layout \begin_layout Plain Layout export(Color,RGBA) var col # Color is RGBA \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout \end_layout \end_inset \end_layout \begin_layout Standard 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 \begin_inset Quotes eld \end_inset tool \begin_inset Quotes erd \end_inset ). \end_layout \begin_layout Subsection Static Functions \end_layout \begin_layout Standard A function can be declared static. When static, it has no access to the instance member variables or \begin_inset Quotes eld \end_inset self \begin_inset Quotes erd \end_inset . This is mainly useful to make libraries of helper functions: \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout static func sum2(a,b): \end_layout \begin_layout Plain Layout return a+b \end_layout \end_inset \end_layout \begin_layout Subsection Asserting \end_layout \begin_layout Standard It is possible to assert a condition, which will cause a debugger break if false. Just use the built-in 'assert' function. \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout assert(a==2) \end_layout \begin_layout Plain Layout # if a is not 2, it will generate a debugger break \end_layout \end_inset \end_layout \begin_layout Subsection Tool Mode \end_layout \begin_layout Standard 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 (as long as they don't execute game code or manually avoid doing so). For this, the \begin_inset Quotes eld \end_inset tool \begin_inset Quotes erd \end_inset keyword exists, and must be placed at the top of the file: \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout tool \end_layout \begin_layout Plain Layout extends Button \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout func _init(): \end_layout \begin_layout Plain Layout print("Hello") \end_layout \end_inset \end_layout \begin_layout Subsection Memory Management \end_layout \begin_layout Standard If a class inherits from \emph on Reference \emph default , then instances will be freed when no longer in use. No garbage collector exists, just simple reference counting. By default, all classes that don't define inheritance extend \emph on Reference \emph default . If this is not desired, then a class must inherit \emph on Object \emph default manually and must call instance.free(). To avoid reference cycles that can't be freed, a weakref() function is provided for creating weak references. \end_layout \begin_layout Subsection Function References \end_layout \begin_layout Standard Functions can't be referenced because they are not treated as class members. There are two alternatives to this, though. The \begin_inset Quotes eld \end_inset call \begin_inset Quotes erd \end_inset function or the funcref() helper. \end_layout \begin_layout Standard \begin_inset listings inline false status open \begin_layout Plain Layout instance.call("funcname",args) # call a function by bane \end_layout \begin_layout Plain Layout \end_layout \begin_layout Plain Layout var fr = funcref(instance,"funcname") #create a function ref \end_layout \begin_layout Plain Layout fr.exec(args) \end_layout \end_inset \end_layout \end_body \end_document