overview.md

Overview

This will be a living doc which will provide an overview of key concepts in the godot-go bidnings.

GDScript Language Feature Mapping

There are a lot of language features supported by GDScript that does not map cleanly to Go.

Default Parameter Value

Default parameters are currently not supported.

Class Inheritance

Go does not support classical class inheritance. Instead, composition with struct embedding is used in it's place. Lets take a look at the following example user-defined class:

type PlayerCharacter struct {
	CharacterBody2DImpl
}

// interface test evidence
var _ CharacterBody2D = &PlayerCharacter{}

The user-defined PlayerCharacter class extends the CharacterBody2D interface by embedding the CharacterBody2DImpl struct. Following the definition of CharacterBody2DImpl we see the following definition:

type CharacterBody2DImpl struct {
	PhysicsBody2DImpl
}

We see that CharacterBody2DImpl embeds the PhysicsBody2DImpl struct, which implements the PhysicsBody2D interface.

Virtual Methods

Go does not natively support virtual functions or struct methods. Insteead, a method name prefix convention will be implemented. The current implementation ignores all virtual methods on existing Godot classes.

func (e *Example) V_Ready() { ... }

...

// register the function with Godot
ClassDBBindMethodVirtual(t, "V_Ready", "_ready", nil, nil)

(NOT YET IMPLEMENTED) The eventual best practice will be the following example:

func (e *Example) V_Example_Ready() { ... }

...

// register the function with Godot
ClassDBBindMethodVirtual(t, "V_Example_Ready", "_ready", nil, nil)

• V_ denotes this this is a virtual function.
• Example_ matches the name of the class. godot-go should panic if the registered method does not follow this pattern.
• Ready matches _ready gdscript method.

Default Argument Values

Go does not support default parameter values. Default argument will show up in the godocs comments, but it will not be implemented directly in the code.

Static Methods

Go does not support static methods in structs. Registering static methods is not supported.

Static Variables

Go does not support static variables in structs. (NOT YET IMPLEMENTED) Global variables can be registered as gdscript static variables.

Packed Arrays

Works fine and partially tested in the tests.

Coroutines

Go does not support coroutines; this means we do not have acess to await (or yield). Without a coroutine alternative, a cumbersome pattern of chaining method calls will be required. (NOT YET IMPLEMENTED) Instead, we have goroutines to wrap signal and callable.

Built-in Types

Basic Built-in Types

GDScript Type	Go Type	Description
null	nil
bool	bool
int	int64	All method parameters that use variations of uint and int will be converted to int64 before passing over the value to Godot.
float	float64	float32 will convert to float64 before passing over the value to Godot.
String	String	There are helper functions to convert to go native string.
StringName	StringName	There are helper functions to convert to go native string.
NodePath	NodePath

Vector Built-in Types

GDScript Type	Go Type
Vector2	Vector2
Vector2i	Vector2i
Rect2	Rect2
Vector3	Vector3
Vector3i	Vector3i
Transform2D	Transform2D
Plane	Plane
Quaternion	Quaternion
AABB	AABB
Basis	Basis
Transform3D	Transform3D

Engine built-in Types

GDScript Type	Go Type
Color	Color
RID	RID
Object	Object

Container Built-in Types

GDScript Type	Go Type	Description
Array	Array	(NOT YET IMPLEMENTED) []Variant.
PackedByteArray	PackedByteArray	(NOT YET IMPLEMENTED) []byte.
PackedInt32Array	PackedInt32Array	(NOT YET IMPLEMENTED) []int32.
PackedInt64Array	PackedInt64Array	(NOT YET IMPLEMENTED) []int64.
PackedFloat32Array	PackedFloat32Array	(NOT YET IMPLEMENTED) []float32.
PackedFloat64Array	PackedFloat64Array	(NOT YET IMPLEMENTED) []float64.
PackedStringArray	PackedStringArray	(NOT YET IMPLEMENTED) []string.
PackedVector2Array	PackedVector2Array	(NOT YET IMPLEMENTED) []Vector2.
PackedVector3Array	PackedVector3Array	(NOT YET IMPLEMENTED) []Vector3.
PackedColorArray	PackedColorArray	(NOT YET IMPLEMENTED) []color.
Dictionary	Dictionary	No additional work needed.
Signal	Signal	No additional work needed.
Callable	Callable	No additional work needed.