Chandler Freeman Chandler Freeman - 2 months ago 10
Node.js Question

How do I update my function to use the new v8 FunctionTemplates?

I have some code that used V8 FunctionTemplates. It is part of an older Node.js module that acts as a wrapper for a C++ library.

void NNet::PrototypeInit(Local<FunctionTemplate> t)
{
...

t->InstanceTemplate()->SetAccessor(Nan::New<String>("training_algorithm").ToLocalChecked(), GetTrainingAlgorithm, SetTrainingAlgorithm);
t->InstanceTemplate()->SetAccessor(Nan::New<String>("learning_rate").ToLocalChecked(), GetLearningRate, SetLearningRate);
t->InstanceTemplate()->SetAccessor(Nan::New<String>("learning_momentum").ToLocalChecked(), GetLearningMomentum, SetLearningMomentum);
t->InstanceTemplate()->SetAccessor(Nan::New<String>("layers").ToLocalChecked(), GetLayerArray);
}


However, when the code is run, the compiler gives these errors.

In static member function ‘static void NNet::PrototypeInit(v8::Local<v8::FunctionTemplate>)’:
error: invalid conversion from ‘Nan::NAN_GETTER_RETURN_TYPE (*)(v8::Local<v8::String>, Nan::NAN_GETTER_ARGS_TYPE) {aka void (*)(v8::Local<v8::String>, const Nan::PropertyCallbackInfo<v8::Value>&)}’ to ‘v8::AccessorGetterCallback {aka void (*)(v8::Local<v8::String>, const v8::PropertyCallbackInfo<v8::Value>&)}’ [-fpermissive]
t->InstanceTemplate()->SetAccessor(Nan::New<String>("training_algorithm").ToLocalChecked(), GetTrainingAlgorithm, SetTrainingAlgorithm);
^
error: initializing argument 2 of ‘void v8::ObjectTemplate::SetAccessor(v8::Local<v8::String>, v8::AccessorGetterCallback, v8::AccessorSetterCallback, v8::Local<v8::Value>, v8::AccessControl, v8::PropertyAttribute, v8::Local<v8::AccessorSignature>)’ [-fpermissive]
void SetAccessor(
^
error: invalid conversion from ‘Nan::NAN_SETTER_RETURN_TYPE (*)(v8::Local<v8::String>, v8::Local<v8::Value>, Nan::NAN_SETTER_ARGS_TYPE) {aka void (*)(v8::Local<v8::String>, v8::Local<v8::Value>, const Nan::PropertyCallbackInfo<void>&)}’ to ‘v8::AccessorSetterCallback {aka void (*)(v8::Local<v8::String>, v8::Local<v8::Value>, const v8::PropertyCallbackInfo<void>&)}’ [-fpermissive]
t->InstanceTemplate()->SetAccessor(Nan::New<String>("training_algorithm").ToLocalChecked(), GetTrainingAlgorithm, SetTrainingAlgorithm);


The documentation for the V8 engine says

The following example shows how to use a FunctionTemplate:
*
* \code
* v8::Local<v8::FunctionTemplate> t = v8::FunctionTemplate::New();
* t->Set("func_property", v8::Number::New(1));
*
* v8::Local<v8::Template> proto_t = t->PrototypeTemplate();
* proto_t->Set("proto_method", v8::FunctionTemplate::New(InvokeCallback));
* proto_t->Set("proto_const", v8::Number::New(2));
*
* v8::Local<v8::ObjectTemplate> instance_t = t->InstanceTemplate();
* instance_t->SetAccessor("instance_accessor", InstanceAccessorCallback);
* instance_t->SetNamedPropertyHandler(PropertyHandlerCallback, ...);
* instance_t->Set("instance_property", Number::New(3));
*
* v8::Local<v8::Function> function = t->GetFunction();
* v8::Local<v8::Object> instance = function->NewInstance();
* \endcode


but I'm not sure how to use this to fix my function. Any ideas?

Answer

Solution was to use

  Nan::SetAccessor(t->InstanceTemplate(), Nan::New<String>("training_algorithm").ToLocalChecked(), GetTrainingAlgorithm, SetTrainingAlgorithm);
  Nan::SetAccessor(t->InstanceTemplate(), Nan::New<String>("learning_rate").ToLocalChecked(), GetLearningRate, SetLearningRate);
  Nan::SetAccessor(t->InstanceTemplate(), Nan::New<String>("learning_momentum").ToLocalChecked(), GetLearningMomentum, SetLearningMomentum);
  Nan::SetAccessor(t->InstanceTemplate(), Nan::New<String>("layers").ToLocalChecked(), GetLayerArray);

instead. This was changed from nan library version 1 to version 2.

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