Solved my problem. I had to use point_constructor->InstanceTemplate() only
to set the internal field count. To set the methods I need to use
point_constructor->PrototypeTemplate().
Still struggling a bit to understand *why* it has to be that way. V8
internals is kind of a mystery.
On Monday, November 7, 2016 at 1:14:14 PM UTC-2, George Marques wrote:
>
> I'm trying to embed V8 5.4 into a game engine. I want to expose the engine
> types to JavaScript as ES6 classes.
>
> I am actually able to do that, but when I extend the class in JavaScript
> the methods are not being overridden by the JS code.
>
> Here's a sample of how I am doing it:
>
> class Point {
> public:
> int x;
> int y;
> int sum() { return x + y; }
> };
>
>
> void PointConstructor(const FunctionCallbackInfo<Value>& args) {
> Isolate* isolate = args.GetIsolate();
> if (!args.IsConstructCall()) {
> isolate->ThrowException(String::NewFromUtf8(isolate, "Can only be
> called as constructor."));
> return;
> }
>
> Point* p = new Point();
> p->x = args[0]->IntegerValue();
> p->y = args[1]->IntegerValue();
>
>
> args.This()->SetInternalField(0, External::New(isolate, p));
> }
>
>
> void PointSum(const FunctionCallbackInfo<Value>& args) {
> Local<External> field = Local<External>::Cast(args.This()->
> GetInternalField(0));
> Point* p = static_cast<Point*>(field->Value());
>
> args.GetReturnValue().Set(p->sum());
> }
>
>
> int main(int argc, char* argv[]) {
> // ... initialize V8
>
> // Create the global object with print function for test
> Local<ObjectTemplate> global = ObjectTemplate::New(isolate);
> global->Set(String::NewFromUtf8(isolate, "print"), FunctionTemplate::New
> (isolate, PrintCallback));
>
> // Create the point constructor template
> Local<FunctionTemplate> point_constructor = FunctionTemplate::New(
> isolate, PointConstructor);
> Local<ObjectTemplate> point_template = point_constructor->
> InstanceTemplate();
> point_template->SetInternalFieldCount(1);
> point_template->Set(String::NewFromUtf8(isolate, "sum"),
> FunctionTemplate::New(isolate, PointSum));
> point_template->SetHandler(NamedPropertyHandlerConfiguration(NamedGet));
>
> // Add the constructor to the global object as the type
> global->Set(String::NewFromUtf8(isolate, "Point"), point_constructor);
>
> // ... compile and run code.
> }
>
>
> And here is the Java Script code:
>
> class MyPoint extends Point {
> sum() {
> return 25;
> }
> }
>
> var p = new MyPoint(2, 3);
> print(p.sum()) // Prints 5, using the native function
>
>
> My problem is that the sum() method of the child type is not called if
> the parent method is native. Is there a way to enforce the overriding?
>
>
--
--
v8-users mailing list
[email protected]
http://groups.google.com/group/v8-users
---
You received this message because you are subscribed to the Google Groups
"v8-users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
