Cross-language scripting

Godot allows you to mix and match scripting languages to suit your needs. This means a single project can define nodes in both C# and GDScript. This page will go through the possible interactions between two nodes written in different languages.

The following two scripts will be used as references throughout this page.

extends Node

var str1 : String = "foo"
var str2 : String setget ,get_str2

func get_str2() -> String:
    return "foofoo"

func print_node_name(node : Node) -> void:
    print(node.get_name())

func print_array(arr : Array) -> void:
    for element in arr:
        print(element)

func print_x_times(msg : String, n : int) -> void:
    for i in range(n):
        print(msg)
public class MyCSharpNode : Node
{
    public String str1 = "bar";
    public String str2 { get { return "barbar"; } }

    public void PrintNodeName(Node node)
    {
        GD.Print(node.GetName());
    }

    public void PrintArray(String[] arr)
    {
        foreach (String element in arr)
        {
            GD.Print(element);
        }
    }

    public void PrintNTimes(String msg, int n)
    {
        for (int i = 0; i < n; ++i)
        {
            GD.Print(msg);
        }
    }
}

Istanziare nodi

If you're not using nodes from the scene tree, you'll probably want to instantiate nodes directly from the code.

Instantiating C# nodes from GDScript

Using C# from GDScript doesn't need much work. Once loaded (see Classes as resources), the script can be instantiated with new().

var my_csharp_script = load("res://path_to_cs_file.cs")
var my_csharp_node = my_csharp_script.new()
print(my_csharp_node.str2) # barbar

Avvertimento

When creating .cs scripts, you should always keep in mind that the class Godot will use is the one named like the .cs file itself. If that class does not exist in the file, you'll see the following error: Invalid call. Nonexistent function `new` in base.

For example, MyCoolNode.cs should contain a class named MyCoolNode.

You also need to check your .cs file is referenced in the project's .csproj file. Otherwise, the same error will occur.

Instantiating GDScript nodes from C#

From the C# side, everything work the same way. Once loaded, the GDScript can be instantiated with GDScript.New().

GDScript MyGDScript = (GDScript) GD.Load("res://path_to_gd_file.gd");
Object myGDScriptNode = (Godot.Object) MyGDScript.New(); // This is a Godot.Object

Here we are using an Object, but you can use type conversion like explained in Type conversion and casting.

Accessing fields

Accessing C# fields from GDScript

Accessing C# fields from GDScript is straightforward, you shouldn't have anything to worry about.

print(my_csharp_node.str1) # bar
my_csharp_node.str1 = "BAR"
print(my_csharp_node.str1) # BAR

print(my_csharp_node.str2) # barbar
# my_csharp_node.str2 = "BARBAR" # This line will hang and crash

Note that it doesn't matter if the field is defined as a property or an attribute. However, trying to set a value on a property that does not define a setter will result in a crash.

Accessing GDScript fields from C#

As C# is statically typed, accessing GDScript from C# is a bit more convoluted, you will have to use Object.Get() and Object.Set(). The first argument is the name of the field you want to access.

GD.Print(myGDScriptNode.Get("str1")); // foo
myGDScriptNode.Set("str1", "FOO");
GD.Print(myGDScriptNode.Get("str1")); // FOO

GD.Print(myGDScriptNode.Get("str2")); // foofoo
// myGDScriptNode.Set("str2", "FOOFOO"); // This line won't do anything

Keep in mind that when setting a field value you should only use types the GDScript side knows about. Essentially, you want to work with built-in types as described in Basi di GDScript or classes extending Object.

Calling methods

Calling C# methods from GDScript

Again, calling C# methods from GDScript should be straightforward. The marshalling process will do its best to cast the arguments to match function signatures. If that's impossible, you'll see the following error: Invalid call. Nonexistent function `FunctionName`.

my_csharp_node.PrintNodeName(self) # myGDScriptNode
# my_csharp_node.PrintNodeName() # This line will fail.

my_csharp_node.PrintNTimes("Hello there!", 2) # Hello there! Hello there!

my_csharp_node.PrintArray(["a", "b", "c"]) # a, b, c
my_csharp_node.PrintArray([1, 2, 3]) # 1, 2, 3

Calling GDScript methods from C#

To call GDScript methods from C# you'll need to use Object.Call(). The first argument is the name of the method you want to call. The following arguments will be passed to said method.

myGDScriptNode.Call("print_node_name", this); // my_csharp_node
// myGDScriptNode.Call("print_node_name"); // This line will fail silently and won't error out.

myGDScriptNode.Call("print_n_times", "Hello there!", 2); // Hello there! Hello there!

// When dealing with functions taking a single array as arguments, we need to be careful.
// If we don't cast it into an object, the engine will treat each element of the array as a separate argument and the call will fail.
String[] arr = new String[] { "a", "b", "c" };
// myGDScriptNode.Call("print_array", arr); // This line will fail silently and won't error out.
myGDScriptNode.Call("print_array", (object)arr); // a, b, c
myGDScriptNode.Call("print_array", (object)new int[] { 1, 2, 3 }); // 1, 2, 3
// Note how the type of each array entry does not matter as long as it can be handled by the marshaller

Avvertimento

As you can see, if the first argument of the called method is an array, you'll need to cast it as object. Otherwise, each element of your array will be treated as a single argument and the function signature won't match.

Ereditarietà

A GDScript file may not inherit from a C# script. Likewise, a C# script may not inherit from a GDScript file. Due to how complex this would be to implement, this limitation is unlikely to be lifted in the future. See this GitHub issue for more information.