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94 lines
2.9 KiB
ReStructuredText
94 lines
2.9 KiB
ReStructuredText
.. _doc_c_sharp_features:
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Features
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============
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This page provied an overview over the commonly used features of both C# and Godot
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and how they are used together.
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Type Conversion and Casting
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---------------------------
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C# is a statically typed language. Therefore you can't do the following:
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.. code-block:: csharp
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var mySprite = GetNode("MySprite")
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mySprite.SetFrame(0)
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The method ``GetNode()`` returns a ``Node`` instance.
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You must explicitly convert it to the desired derived type, ``Sprite`` in this case.
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For this, you have various options in C#.
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**Casting and Type Checking**
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Throws ``InvalidCastException`` if the returned node cannot be casted to Sprite.
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You would use it instead of the ``as`` operator if you are pretty sure it won't fail.
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.. code-block:: csharp
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Sprite mySprite = (Sprite)GetNode("MySprite");
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mySprite.SetFrame(0);
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**Using the AS operator**
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The ``as`` operator returns null if the node cannot be casted to Sprite,
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and for this reason it cannot be used with value types.
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.. code-block:: csharp
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Sprite mySprite = GetNode("MySprite") as Sprite;
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// Only call SetFrame() is mySprite is not null
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mySprite?.SetFrame(0);;
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**Type checking using the IS operator**
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To check if the node can be casted to Sprite, you can use the ``is`` operator.
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The ``is`` operator returns false if the node cannot be casted to Sprite,
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otherwise it returns true.
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.. code-block:: csharp
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if (GetNode("MySprite") is Sprite)
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{
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// Yup, it's a sprite!
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}
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For more advanced type checking, you can look into `Pattern Matching <https://docs.microsoft.com/en-us/dotnet/csharp/pattern-matching>`_.
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Signals
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-------
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For a complete C# example, see the **Handling a signal** section in the step by step :ref:`doc_scripting` tutorial.
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You can use ``Connect("SomeSignal", someObject, "SomeMethod")`` to connect to signals.
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``AddUserSignal("SignalName")`` is used to define custom signals.
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Emitting signals is done with ``EmitSignal("SignalName")``. Params can be given, like ``EmitSignal("SignalName", arg1, arg2, ...)``.
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**Custom signals**
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.. code-block:: csharp
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:emphasize-lines: 5, 10
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:linenos:
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public class ExampleScript : Node
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{
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public override void _Ready()
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{
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AddUserSignal("YourSignal");
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}
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public override void _Process(float delta)
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{
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EmitSignal("YourSignal");
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}
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}
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Above in line 5, ``AddUserSignal()`` is used to define the new custom signal ``YourSignal``.
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In line 10 ``EmitSignal()`` is used to emit that custom signal on every frame in ``_Process()``.
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Make sure that ``AddUserSignal()`` is always executed before any calls using that signal (``EmitSignal()`` and ``Connect()``).
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If you are using both ``AddUserSignal()`` and ``Connect()`` or ``EmitSignal()`` in ``_Ready()``, this is especially important as load order of your node may change,
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and thus the order in which your various ``_Ready()`` functions are called.
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