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Functions

Any Kotlin, Java, or Scala function can be registered as long as its parameters and return type can be converted to a Variant. Annotate ordinary project functions with @Register. Compatible overrides of Godot functions are recognized from the base class.

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@Script
class RotatingCube : Node3D() {
    @Register
    fun announceReady() {
        println("I am ready!")
    }

    override fun _ready() {
        announceReady()
    }
}

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@Script
public class RotatingCube extends Node3D {
    @Register
    public void announceReady() {
        System.out.println("I am ready!");
    }

    @Override
    public void _ready() {
        announceReady();
    }
}

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@Script
class RotatingCube extends Node3D {
  @Register
  def announceReady(): Unit = {
    println("I am ready!")
  }

  override def _ready(): Unit = {
    announceReady()
  }
}

Naming

Function names should follow the usual style of the language you use. For consistency with Godot's style, your functions are actually registered as snake_case. Therefore, a function called doSomething() is usable in GDScript as do_something().

Virtual functions

Virtual functions such as _ready, _process, and _physics_process are declared as overridable functions. Override one to provide its behavior. Because it is already a Godot function, the inherited declaration identifies it without an additional @Register.

Arguments count

Godot limits the allowed argument count of functions to 16. Thus, this binding also has this limitation. If you want to pass more than 16 parameters in a function, you need to wrap them in a container (like a custom container class or a VariantArray or Dictionary).

Customization

@Register only selects an ordinary function. Add a more specific annotation when the function has additional behavior. For example, @Rpc selects the function through its registration meta-annotation and configures its networking behavior at the same time.

See the registration guide for how function selection changes between modes.