Node v0.12 Addons and V8: Returning new objects from exposed functions

[blazs]

Hi,

suppose I have wrapped a vector TJsVec and there's a function static void multiply(const v8::FunctionCallbackInfo<v8::Value>& Args); that returns a new TJsVec, scaled by a scalar:

void TJsVec::multiply(const FunctionCallbackInfo<Value>& Args) {

  Isolate* Isolate = Isolate::GetCurrent();

  HandleScope Scope(Isolate);

  

  /* error checking -- make sure Args.Length() >= 1 and Args[0] is a number */ 

  TJsVec* JsVec = ... /* unwraps the object */ 

  const double Scalar = Args[0]->NumberValue();

  TFloatVector ResV; // ResV = JsVec->Vec * Scalar 

   ... /* scales JsVec->Vec by scalar using internal linear algebra library */

  

   TJsVec* JsResV = new TJsVec(ResV);

   JsResV->Wrap(Args.Holder()); // (1)

   // (2) 

   Args.GetReturnValue().Set(JsResV); // (3)

}

Note that TJsVec is derived from node::ObjectWrap, i.e. we have class TJsVec : public node::ObjectWrap { ... };.

I have several questions regarding this code:

 (*) What exactly does the line JsResV->Wrap(Args.Holder()) do? Why do we pass it Args.Holder()?

 (*) What does Args.GetReturnValue().Set(JsResV); do? 

 (*) And, most important, suppose I executed Javascript function in the place (2). Could V8 garbage-collected JsResV? I.e. is object elligible for delition at (2) -- immediately after creation and before the function "returns" it in (3)? 

Furher, should I move the line (3) immediately after creating the object? 

Blaz.