godot-docs/tutorials/scripting/gdscript/gdscript_exports.rst

.. _doc_gdscript_exports:

GDScript exports
================

Introduction to exports
-----------------------

In Godot, class members can be exported. This means their value gets saved along
with the resource (such as the :ref:`scene <class_PackedScene>`) they're
attached to. They will also be available for editing in the property editor.
Exporting is done by using the ``@export`` annotation::

    extends Button

    @export var number = 5
    
In that example the value `5` will be saved and visible in the property editor.

An exported variable must be initialized to a constant expression or have a type specifier
in the variable. Some of the export annotations have a specific type and don't need the variable to be typed (see the
*Examples* section 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.

Exporting can only be done with built-in types or objects derived from the :ref:`Resource class <class_Resource>`.

.. note::

    Exporting properties can also be done in other languages such as C#.
    The syntax varies depending on the language.

Basic use
---------

If the exported value assigns a constant or constant expression,
the type will be inferred and used in the editor.

::

    @export var number = 5

If there's no default value, you can add a type to the variable.

::

    @export var number: int

Export works with resource types.

::

    @export var character_face: Texture
    @export var scene_file: PackedScene

There are many resource types that can be used this way, try e.g.
the following to list them:

::

    @export var resource: Resource

Integers and strings hint enumerated values.

    # Editor will enumerate as 0, 1 and 2.
    @export_enum("Warrior", "Magician", "Thief") var character_class

If type is String, editor will enumerate with string names.

::

    @export_enum("Rebecca", "Mary", "Leah") var character_name: String

Named enum values
-----------------

Editor will enumerate as THING_1, THING_2, ANOTHER_THING.

::

    enum NamedEnum {THING_1, THING_2, ANOTHER_THING = -1}
    @export var x: NamedEnum

Strings as paths
----------------

String as a path to a file.

::

    @export_file var f

String as a path to a directory.

::

    @export_dir var f

String as a path to a file, custom filter provided as hint.

::

    @export_file("*.txt") var f

Using paths in the global filesystem is also possible,
but only in scripts in tool mode.

String as a path to a PNG file in the global filesystem.

::

    @export_global_file("*.png") var tool_image

String as a path to a directory in the global filesystem.

::

    @export_global_dir var tool_dir

The multiline annotation tells the editor to show a large input
field for editing over multiple lines.

::

    @export_multiline var text

Limiting editor input ranges
----------------------------

Allow integer values from 0 to 20.

::

    @export_range(0, 20) var i

Allow integer values from -10 to 20.

::

    @export_range(-10, 20) var j

Allow floats from -10 to 20 and snap the value to multiples of 0.2.

::

    @export_range(-10, 20, 0.2) var k: float

The limits can be only for the slider if you add the hints "or_greater" and/or "or_lesser".

::

    @export_range(0, 100, 1, "or_greater", "or_lesser")
    
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_exp_range(100, 1000, 20) var l

Floats with easing hint
-----------------------

Display a visual representation of the 'ease()' function
when editing.

::

    @export_exp_easing var transition_speed

Colors
------

Regular color given as red-green-blue-alpha value.

::

    @export var col: Color

Color given as red-green-blue value (alpha will always be 1).

::

    @export_color_no_alpha var col: Color

Nodes
-----

Nodes can't be directly exported. Instead you need to export
a node path, then use that node path with `get_node()`

::

    @export var node_path: NodePath
    var node = get_node(node_path)

If you want to limit the types of nodes, you can use the @export_node_path annotation.

::

    @export_node_path(Button, TouchScreenButton) var some_button

Resources
---------

::

    @export var resource: Resource

In the Inspector, you can then drag and drop a resource file
from the FileSystem dock into the variable slot.

Opening the inspector dropdown may result in an
extremely long list of possible classes to create, however.
Therefore, if you specify an extension of Resource such as:

    @export var resource: AnimationNode

The drop-down menu will be limited to AnimationNode and all
its inherited classes.

It must be noted that even if the script is not being run while in the
editor, the exported properties are still editable. This can be used
in conjunction with a :ref:`script in "tool" mode <doc_gdscript_tool_mode>`.

Exporting bit flags
-------------------

Integers used as bit flags can store multiple ``true``/``false`` (boolean)
values in one property. By using the ``@export_flags`` annotation, they
can be set from the editor::

    # Set any of the given flags from the editor.
    @export_flags("Fire", "Water", "Earth", "Wind") var spell_elements = 0

You must provide a string description for each flag. 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).

Export annotations are also provided for the physics and render layers defined in the project settings::

    @export_flags_2d_physics var layers_2d_physics
    @export_flags_2d_render var layers_2d_render
    @export_flags_3d_physics var layers_3d_physics
    @export_flags_3d_render var layers_3d_render

Using bit flags requires some understanding of bitwise operations.
If in doubt, use boolean variables instead.

Exporting arrays
----------------

Exported arrays can have initializers, but they must be constant expressions.

If the exported array specifies a type which inherits from Resource, the array
values can be set in the inspector by dragging and dropping multiple files
from the FileSystem dock at once.

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 = [[1.0, 2.0], [3.0, 4.0]]

You can omit the default value, but then it would be null if not assigned.

::

    export(Array) var b
    export(Array, PackedScene) var scenes

Arrays with specified types which inherit from resource can be set by
drag-and-dropping multiple files from the FileSystem dock.

::

    export(Array, Texture) var textures
    export(Array, PackedScene) var scenes

Typed arrays also work, only initialized empty:

::

    export var vector3s = PackedVector3Array()
    export var strings = PackedStringArray()

Default value can include run-time values, but can't
be exported.

::

    var c = [a, 2, 3]

Setting exported variables from a tool script
---------------------------------------------

When changing an exported variable's value from a script in
:ref:`doc_gdscript_tool_mode`, the value in the inspector won't be updated
automatically. To update it, call
:ref:`property_list_changed_notify() <class_Object_method_property_list_changed_notify>`
after setting the exported variable's value.

Advanced exports
----------------

Not every type of export can be provided on the level of the language itself to
avoid unnecessary design complexity. The following describes some more or less
common exporting features which can be implemented with a low-level API.

Before reading further, you should get familiar with the way properties are
handled and how they can be customized with
:ref:`_set() <class_Object_method__get_property_list>`,
:ref:`_get() <class_Object_method__get_property_list>`, and
:ref:`_get_property_list() <class_Object_method__get_property_list>` methods as
described in :ref:`doc_accessing_data_or_logic_from_object`.

.. seealso:: For binding properties using the above methods in C++, see
             :ref:`doc_binding_properties_using_set_get_property_list`.

.. warning:: The script must operate in the ``tool`` mode so the above methods
             can work from within the editor.