.. _doc_c_sharp_differences:

C# API differences to GDScript
==============================

This is a (incomplete) list of API differences between C# and GDScript.

General differences
-------------------

As explained in the :ref:`doc_c_sharp`, C# generally uses ``PascalCase`` instead
of the ``snake_case`` used in GDScript and C++.

Global scope
------------

Global functions and some constants had to be moved to classes, since C#
does not allow declaring them in namespaces.
Most global constants were moved to their own enums.

Constants
^^^^^^^^^

Global constants were moved to their own enums.
For example, ``ERR_*`` constants were moved to the ``Error`` enum.

Special cases:

=======================  ===========================================================
GDScript                 C#
=======================  ===========================================================
``SPKEY``                ``GD.SpKey``
``TYPE_*``               ``Variant.Type`` enum
``OP_*``                 ``Variant.Operator`` enum
=======================  ===========================================================

Math functions
^^^^^^^^^^^^^^

Math global functions, like ``abs``, ``acos``, ``asin``, ``atan`` and ``atan2``, are
located under ``Mathf`` as ``Abs``, ``Acos``, ``Asin``, ``Atan`` and ``Atan2``.
The ``PI`` constant can be found as ``Mathf.Pi``.

Random functions
^^^^^^^^^^^^^^^^

Random global functions, like ``rand_range`` and ``rand_seed``, are located under ``GD``.
Example: ``GD.RandRange`` and ``GD.RandSeed``.

Other functions
^^^^^^^^^^^^^^^

Many other global functions like ``print`` and ``var2str`` are located under ``GD``.
Example: ``GD.Print`` and ``GD.Var2Str``.

Exceptions:

===========================  =======================================================
GDScript                     C#
===========================  =======================================================
``weakref(obj)``             ``Object.WeakRef(obj)``
``is_instance_valid(obj)``   ``Object.IsInstanceValid(obj)``
===========================  =======================================================

Tips
^^^^

Sometimes it can be useful to use the ``using static`` directive. This directive allows
to access the members and nested types of a class without specifying the class name.

Example:

.. code-block:: csharp

    using static Godot.GD;

    public class Test
    {
        static Test()
        {
            Print("Hello"); // Instead of GD.Print("Hello");
        }
    }

Export keyword
--------------

Use the ``[Export]`` attribute instead of the GDScript ``export`` keyword.
This attribute can also be provided with optional :ref:`PropertyHint<enum_@GlobalScope_PropertyHint>` and ``hintString`` parameters.
Default values can be set by assigning a value.

Example:

.. code-block:: csharp

    using Godot;

    public class MyNode : Node
    {
        [Export]
        private NodePath _nodePath;

        [Export]
        private string _name = "default";

        [Export(PropertyHint.Range, "0,100000,1000,or_greater")]
        private int _income;

        [Export(PropertyHint.File, "*.png,*.jpg")]
        private string _icon;
    }

Signal keyword
--------------

Use the ``[Signal]`` attribute to declare a signal instead of the GDScript ``signal`` keyword.
This attribute should be used on a `delegate`, whose name signature will be used to define the signal.

.. code-block:: csharp

    [Signal]
    delegate void MySignal(string willSendsAString);

See also: :ref:`doc_c_sharp_signals`.

`onready` keyword
-----------------

GDScript has the ability to defer the initialization of a member variable until the ready function
is called with `onready` (cf. :ref:`doc_gdscript_onready_keyword`).
For example:

.. code-block:: gdscript

    onready var my_label = get_node("MyLabel")

However C# does not have this ability. To achieve the same effect you need to do this.

.. code-block:: csharp

    private Label _myLabel;

    public override void _Ready()
    {
        _myLabel = GetNode<Label>("MyLabel");
    }

Singletons
----------

Singletons are available as static classes rather than using the singleton pattern.
This is to make code less verbose than it would be with an ``Instance`` property.

Example:

.. code-block:: csharp

    Input.IsActionPressed("ui_down")

However, in some very rare cases this is not enough. For example, you may want
to access a member from the base class ``Godot.Object``, like ``Connect``.
For such use cases we provide a static property named ``Singleton`` that returns
the singleton instance. The type of this instance is ``Godot.Object``.

Example:

.. code-block:: csharp

    Input.Singleton.Connect("joy_connection_changed", this, nameof(Input_JoyConnectionChanged));

String
------

Use ``System.String`` (``string``). Most of Godot's String methods are
provided by the ``StringExtensions`` class as extension methods.

Example:

.. code-block:: csharp

    string upper = "I LIKE SALAD FORKS";
    string lower = upper.ToLower();

There are a few differences, though:

* ``erase``: Strings are immutable in C#, so we cannot modify the string
  passed to the extension method. For this reason, ``Erase`` was added as an
  extension method of ``StringBuilder`` instead of string.
  Alternatively, you can use ``string.Remove``.
* ``IsSubsequenceOf``/``IsSubsequenceOfi``: An additional method is provided,
  which is an overload of ``IsSubsequenceOf``, allowing you to explicitly specify
  case sensitivity:

.. code-block:: csharp

  str.IsSubsequenceOf("ok"); // Case sensitive
  str.IsSubsequenceOf("ok", true); // Case sensitive
  str.IsSubsequenceOfi("ok"); // Case insensitive
  str.IsSubsequenceOf("ok", false); // Case insensitive

* ``Match``/``Matchn``/``ExprMatch``: An additional method is provided besides
  ``Match`` and ``Matchn``, which allows you to explicitly specify case sensitivity:

.. code-block:: csharp

  str.Match("*.txt"); // Case sensitive
  str.ExprMatch("*.txt", true); // Case sensitive
  str.Matchn("*.txt"); // Case insensitive
  str.ExprMatch("*.txt", false); // Case insensitive

Basis
-----

Structs cannot have parameterless constructors in C#. Therefore, ``new Basis()``
initializes all primitive members to their default value. Use ``Basis.Identity``
for the equivalent of ``Basis()`` in GDScript and C++.

The following method was converted to a property with a different name:

====================  ==============================================================
GDScript              C#
====================  ==============================================================
``get_scale()``       ``Scale``
====================  ==============================================================

Transform2D
-----------

Structs cannot have parameterless constructors in C#. Therefore, ``new Transform2D()``
initializes all primitive members to their default value.
Please use ``Transform2D.Identity`` for the equivalent of ``Transform2D()`` in GDScript and C++.

The following methods were converted to properties with their respective names changed:

====================  ==============================================================
GDScript              C#
====================  ==============================================================
``get_rotation()``    ``Rotation``
``get_scale()``       ``Scale``
====================  ==============================================================

Plane
-----

The following method was converted to a property with a *slightly* different name:

================  ==================================================================
GDScript          C#
================  ==================================================================
``center()``      ``Center``
================  ==================================================================

Rect2
-----

The following field was converted to a property with a *slightly* different name:

================  ==================================================================
GDScript          C#
================  ==================================================================
``end``           ``End``
================  ==================================================================

The following method was converted to a property with a different name:

================  ==================================================================
GDScript          C#
================  ==================================================================
``get_area()``    ``Area``
================  ==================================================================

Quat
----

Structs cannot have parameterless constructors in C#. Therefore, ``new Quat()``
initializes all primitive members to their default value.
Please use ``Quat.Identity`` for the equivalent of ``Quat()`` in GDScript and C++.

The following methods were converted to a property with a different name:

=====================  =============================================================
GDScript               C#
=====================  =============================================================
``length()``           ``Length``
``length_squared()``   ``LengthSquared``
=====================  =============================================================

Array
-----

*This is temporary. PoolArrays will need their own types to be used the way they are meant to.*

=====================  ==============================================================
GDScript               C#
=====================  ==============================================================
``Array``              ``Godot.Collections.Array``
``PoolIntArray``       ``int[]``
``PoolByteArray``      ``byte[]``
``PoolFloatArray``     ``float[]``
``PoolStringArray``    ``String[]``
``PoolColorArray``     ``Color[]``
``PoolVector2Array``   ``Vector2[]``
``PoolVector3Array``   ``Vector3[]``
=====================  ==============================================================

``Godot.Collections.Array<T>`` is a type-safe wrapper around ``Godot.Collections.Array``.
Use the ``Godot.Collections.Array<T>(Godot.Collections.Array)`` constructor to create one.

Dictionary
----------

Use ``Godot.Collections.Dictionary``.

``Godot.Collections.Dictionary<T>`` is a type-safe wrapper around ``Godot.Collections.Dictionary``.
Use the ``Godot.Collections.Dictionary<T>(Godot.Collections.Dictionary)`` constructor to create one.

Variant
-------

``System.Object`` (``object``) is used instead of ``Variant``.

Communicating with other scripting languages
--------------------------------------------

This is explained extensively in :ref:`doc_cross_language_scripting`.

Yield
-----

Something similar to GDScript's ``yield`` with a single parameter can be achieved with
C#'s `yield keyword <https://docs.microsoft.com/en-US/dotnet/csharp/language-reference/keywords/yield>`_.

The equivalent of yield on signal can be achieved with async/await and ``Godot.Object.ToSignal``.

Example:

.. code-block:: csharp

  await ToSignal(timer, "timeout");
  GD.Print("After timeout");

Other differences
-----------------

``preload``, as it works in GDScript, is not available in C#.
Use ``GD.Load`` or ``ResourceLoader.Load`` instead.

Other differences:

================  ==================================================================
GDScript          C#
================  ==================================================================
``Color8``        ``Color.Color8``
``is_inf``        ``float.IsInfinity``
``is_nan``        ``float.IsNaN``
``dict2inst``     TODO
``inst2dict``     TODO
================  ==================================================================