Native Abstractions for Node.js (NAN)

The Nan::MakeCallback() functions are deprecated in Node.js 10+ because they do not provide a mechanism to preserve async context.

Recommendation: Use the AsyncResource class and AsyncResource::runInAsyncScope instead of Nan::MakeCallback or v8::Function#Call() to ensure compatibility with async_hooks, domains, and async debugging.

NAN_DEPRECATED
v8::Local<v8::Value> Nan::MakeCallback(v8::Local<v8::Object> target,
                                       v8::Local<v8::Function> func,
                                       int argc,
                                       v8::Local<v8::Value>* argv);

NAN_DEPRECATED
v8::Local<v8::Value> Nan::MakeCallback(v8::Local<v8::Object> target,
                                       v8::Local<v8::String> symbol,
                                       int argc,
                                       v8::Local<v8::Value>* argv);

NAN_DEPRECATED
v8::Local<v8::Value> Nan::MakeCallback(v8::Local<v8::Object> target,
                                       const char* method,
                                       int argc,
                                       v8::Local<v8::Value>* argv);

If you are attempting to compile against Node.js 0.12 on OSX using modern compilers, you may encounter a V8 header error where CreateHandle is a protected member of v8::HandleScope.

Error Example:

CXX(target) Release/obj.target/accessors/cpp/accessors.o
In file included from ../cpp/accessors.cpp:9:
In file included from ../../nan.h:51:
In file included from /Users/ofrobots/.node-gyp/0.12.18/include/node/node.h:61:
/Users/ofrobots/.node-gyp/0.12.18/include/node/v8.h:5800:54: error: 'CreateHandle' is a protected member of 'v8::HandleScope'
  return Handle<T>(reinterpret_cast<T*>(HandleScope::CreateHandle(
                                        ~~~~~~~~~~~~~^~~~~~~~~~~~~~

Workarounds:

1. Use an older compiler compatible with the Node.js 0.12 era.
2. Apply a source patch to your local V8 headers (corresponding to Node 0.12) to make v8::Handle a friend of v8::HandleScope.

You can implement a factory pattern where a JavaScript function returns new instances of a wrapped C++ class. This is done by creating a Nan::ObjectWrap class and providing a static method (e.g., NewInstance) that uses Nan::NewInstance to return a new object.

C++ Implementation Pattern

1. Inherit from Nan::ObjectWrap.
2. Set InstanceTemplate()->SetInternalFieldCount(1).
3. Implement a New method to handle IsConstructCall() (for new MyObject()) and non-construct calls (for factory usage).
4. Use obj->Wrap(info.This()) inside the constructor logic.

class MyFactoryObject : public Nan::ObjectWrap {
 public:
  static NAN_MODULE_INIT(Init) {
    v8::Local<v8::FunctionTemplate> tpl = Nan::New<v8::FunctionTemplate>(New);
    tpl->InstanceTemplate()->SetInternalFieldCount(1);

    Nan::SetPrototypeMethod(tpl, "getValue", GetValue);

    constructor().Reset(Nan::GetFunction(tpl).ToLocalChecked());
  }

  static NAN_METHOD(NewInstance) {
    v8::Local<v8::Function> cons = Nan::New(constructor());
    double value = info[0]->IsNumber() ? Nan::To<double>(info[0]).FromJust() : 0;
    const int argc = 1;
    v8::Local<v8::Value> argv[1] = {Nan::New(value)};
    info.GetReturnValue().Set(Nan::NewInstance(cons, argc, argv).ToLocalChecked());
  }

  inline double value() const { return value_; }

 private:
  explicit MyFactoryObject(double value = 0) : value_(value) {}
  ~MyFactoryObject() {}

  static NAN_METHOD(New) {
    if (info.IsConstructCall()) {
      double value = info[0]->IsNumber() ? Nan::To<double>(info[0]).FromJust() : 0;
      MyFactoryObject * obj = new MyFactoryObject(value);
      obj->Wrap(info.This());
      info.GetReturnValue().Set(info.This());
    } else {
      const int argc = 1;
      v8::Local<v8::Value> argv[argc] = {info[0]};
      v8::Local<v8::Function> cons = Nan::New(constructor());
      info.GetReturnValue().Set(Nan::NewInstance(cons, argc, argv).ToLocalChecked());
    }
  }

  static NAN_METHOD(GetValue) {
    MyFactoryObject* obj = ObjectWrap::Unwrap<MyFactoryObject>(info.Holder());
    info.GetReturnValue().Set(obj->value_);
  }

  static inline Nan::Persistent<v8::Function> & constructor() {
    static Nan::Persistent<v8::Function> my_constructor;
    return my_constructor;
  }

  double value_;
};

NAN_MODULE_INIT(Init) {
  MyFactoryObject::Init(target);
  Nan::Set(target,
    Nan::New<v8::String>("newFactoryObjectInstance").ToLocalChecked(),
    Nan::GetFunction(
      Nan::New<v8::FunctionTemplate>(MyFactoryObject::NewInstance)).ToLocalChecked()
  );
}

NODE_MODULE(wrappedobjectfactory, Init)