How to use DefineAccessorProperty

[qazwsxedckll]

What I am trying to do is when property of an object is accessed in javascript, some value in go can be returned and when the property is assigned in javascript, the value in go can be changed.

The go value is very complicated so ToValue() does not work.

So I wrote something like

o.DefineAccessorProperty("key", vm.ToValue(getPropertyValue), vm.ToValue(setPropertyValue), goja.FLAG_TRUE, goja.FLAG_TRUE)

But getPropertyValue and setPropertyValue cannot get the name of the property which is key or this in javascript.

Something like this in v8

class Point {
 public:
  Point(int x, int y) : x_(x), y_(y) { }
  int x_, y_;
}

point_templ->SetAccessor(v8::String::NewFromUtf8(isolate, "x"),
                         GetPointX, SetPointX);
point_templ->SetAccessor(v8::String::NewFromUtf8(isolate, "y"),
                         GetPointY, SetPointY);

void GetPointX(Local<String> property,
               const PropertyCallbackInfo<Value>& info) {
  v8::Local<v8::Object> self = info.Holder();
  v8::Local<v8::External> wrap =
      v8::Local<v8::External>::Cast(self->GetInternalField(0));
  void* ptr = wrap->Value();
  int value = static_cast<Point*>(ptr)->x_;
  info.GetReturnValue().Set(value);
}

void SetPointX(v8::Local<v8::String> property, v8::Local<v8::Value> value,
               const v8::PropertyCallbackInfo<void>& info) {
  v8::Local<v8::Object> self = info.Holder();
  v8::Local<v8::External> wrap =
      v8::Local<v8::External>::Cast(self->GetInternalField(0));
  void* ptr = wrap->Value();
  static_cast<Point*>(ptr)->x_ = value->Int32Value();
}

Or maybe Proxy can do the job?

This is my final result

var (
	i  interface{}
	vm *goja.Runtime
)

func main() {
	vm = goja.New()
	o := vm.NewObject()
	o.DefineAccessorProperty("a", vm.ToValue(getter), vm.ToValue(setter), goja.FLAG_FALSE, goja.FLAG_FALSE)
	vm.Set("o", o)

	vm.RunString(`o.a = 1`)
	fmt.Printf("i: %v\n", i)

	i = 3
	fmt.Printf("o.Get(\"a\").Export(): %v\n", o.Get("a").Export())
}

func getter(call goja.FunctionCall) goja.Value {
	return vm.ToValue(i)
}

func setter(call goja.FunctionCall) goja.Value {
	i = call.Arguments[0].Export()
	return goja.Null()
}

Is this how it supposed to use?

Is it right to return goja.Null() in func setter?

[dop251]

Sorry, I don't understand exactly what you're trying to achieve. DefineAccessorProperty just mirrors Object.defineProperty allowing you to do the same from Go code, rather than from JS.

The setter return value is ignored, you can simply return nil.