How should I instantiate a Go struct to return it in a method and then use it on GDScript?

[pafuent]

I have this Go code...

type Bar struct {
	gd.Class[Bar, gd.Object]

	Message gd.String
}

type Foo struct {
	gd.Class[Foo, gd.Object]
}

func (k *Bar) GetBar(ctx gd.Context, message gd.String) gd.Object {
	return gd.Create(ctx, &Bar{Message: message}).AsObject()
}

...then on a GDScript I create a Foo instance and call GetBar...

	var foo: Foo = Foo.new()
	var bar = foo.GetBar("Hello!!!")
	print(bar.Message)

...but when I run it a got this error: SCRIPT ERROR: Invalid get index 'Message' (on base: 'null instance').

Reading the code I think the problem is here. This line always return true due to the previous line, so I always get native.(T) instead of ptr

If I change GetBar to be like this...

func (k *Bar) GetBar(ctx gd.Context, message gd.String) gd.Object {
	ptr := new(Bar)
	object := ctx.API.ClassDB.ConstructObject(ctx, ctx.StringName(strings.TrimPrefix(reflect.TypeOf(ptr).Elem().Name(), "class")))
	object.Set(ctx.StringName("Message"), ctx.Variant(message))
	ptr.SetPointer(object.AsPointer())
	return ptr.AsObject()
}

...it's works as I expect.

Also I'm wondering how I should write GetBar to not call object.Set(ctx.StringName("Message"), ctx.Variant(message)) to set the value of Message on bar. In other words: Is there a way to set Message on Go Bar instance instead of using Object.Set?

[Splizard]

I would expect this to work:

func (k *Bar) GetBar(godot gd.Context, message gd.String) gd.Object {
	var result = gd.Create(godot, new(Bar))
        result.Message = message
        return result.AsObject()
}

You should only pass uninitialised pointers to gd.Create (as indicated in the function's comment).

[pafuent]

I tried that, but returns the error that I mentioned before: SCRIPT ERROR: Invalid get index 'Message' (on base: 'null instance').

[pafuent]

I got it working using Pin()

func (f *Foo) GetBar(ctx gd.Context, message gd.String) gd.Object {
	if f.ctx.API == nil {
		f.ctx = f.Pin()
	}
	var result = gd.Create(f.ctx, new(Bar))
	result.Message = message.Copy(f.ctx)
	return result.AsObject()
}

If I got it correctly, what I'm doing here is to tie Bar instance to a context that will be hold and handled by Foo.

[Splizard]

@pafuent I have made some changes around gd.Context to hopefully improve the experience here, you can do the following now and I can confirm this works with the latest master:

func (f *Foo) GetBar(message gd.String) gd.Object {
	var result = gd.Create(f.Temporary, new(Bar)) // temporary reference.
	result.Message = message.Copy(result.KeepAlive) // keeps the copy alive for the lifetime of 'result'
	return result.AsObject() // godot gains ownership of the object.
}

[TeddyDD]

Does it needs to be returned as gd.Object or can you return the struct directly?

[Splizard]

At the moment, a gd.Object but in future, other values will be supported.