如何更新我的函数以使用新的 v8 FunctionTemplates？答案

【问题标题】：How do I update my function to use the new v8 FunctionTemplates?如何更新我的函数以使用新的 v8 FunctionTemplates？
【发布时间】：2015-10-28 05:25:51
【问题描述】：

我有一些使用 V8 FunctionTemplates 的代码。它是旧 Node.js 模块的一部分，充当 C++ 库的包装器。

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);
}

但是，当代码运行时，编译器会给出这些错误。

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);

V8 引擎的文档说

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

但我不确定如何使用它来修复我的功能。有什么想法吗？

【问题讨论】：

标签： c++ node.js v8 node.js-addon

【解决方案1】：

SetTrainingAlgorithm 的签名是：

void SetTrainingAlgorithm(v8::Local<v8::String>,
                          const Nan::PropertyCallbackInfo<v8::Value>&);

但应该是：

void SetTrainingAlgorithm(v8::Local<v8::String>,
                          const v8::PropertyCallbackInfo<v8::Value>&);

不是同一个命名空间。

【讨论】：

【解决方案2】：

解决方案是使用

  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);

相反。这已从 nan 库版本 1 更改为版本 2。

【讨论】：