是否可以使用私有js构造函数在节点-addon中创建ObjectWrap，并且只能在c++中进行实例化？

Question

我目前正在使用node.js在c++中使用node-addon-api (Napi)编写一个node-addon-api (Napi)插件。从我在不同的文档和教程中看到的情况来看，每个objet都必须扩展Napi::ObjectWrap才能被视为js对象。然后可以在js中调用构造函数。但是，如果我希望这个特定的对象仅由另一个对象提供，并将js构造函数变为私有，又会怎样呢？考虑到这个案子

class Provided: public Napi::ObjectWrap<Provided> {
public:
   // Init function for exports
   static Init(Napi::Env, Napi::Object exports);
   // what if I want my constructor to have a value instead of a CallbackInfo and only allow instantiation from c++ ?
   Provided(std::string value);
private:
   std::string m_value;
};

class MyProvider: public Napi::ObjectWrap<MyProvider> {
public:
   // Init function for exports
   static Init(Napi::Env, Napi::Object exports) {
      Napi::Function func = DefineClass(env, "provider", {InstanceMethod("getProvided", &MyProvider::GetProvided)});

      constructor = Napi::Persistent(func);
      constructor.SupressDestruct();

      exports.Set("Provider", func);
      return exports;
   }
   MyProvider(Napi::CallbackInfo const&): Napi::ObjectWrap<MyProvider>(info) {
       this->m_provided = Provided("my value");

   }
private:
   Provided m_provided;
   static Napi::FunctionReference constructor;
}

如何能够在提供的构造函数中不包含Napi::CallbackInfo

Answer 1

我的解决方案是使用data参数DefineClass来传递我的参数(在我的例子中，只有一个，但我想您可以通过任意数量的容器传递数组/向量/任何容器)。然后，我创建了一个“提供”类的实例并返回它。但有一个例子比我的解释更有价值：

class Provided: public Napi::ObjectWrap<Provided> {
public:
   // Factory for a JavaScript class instance
   static Create(Napi::Env env, std::string &myString) {
      // Pass the argument(s) as last DefineClass argument
      Napi::Function func = DefineClass(env, "provided", {InstanceMethod("getString", &MyProvider::GetString)}, &myString);
   };
   Provided(const Napi::CallbackInfo &info) {
      // And get the c++ object back in the constructor.
      // It requires a cast as it goes through being a void pointer.
      myValue = *(std::string *)info.Data();
   };
private:
   std::string myValue;
   Napi::Value GetString(const Napi::CallbackInfo &info) {
      return Napi::String::New(info.Env(), myValue);
   };
};

class MyProvider: public Napi::ObjectWrap<MyProvider> {
public:
   // Init function for exports
   static Init(Napi::Env env, Napi::Object exports) {
      Napi::Function func = DefineClass(env, "provider", {InstanceMethod("getProvided", &MyProvider::GetProvided)});

      constructor = Napi::Persistent(func);
      constructor.SupressDestruct();

      exports.Set("Provider", func);
      return exports;
   }
   MyProvider(Napi::CallbackInfo const&): Napi::ObjectWrap<MyProvider>(info) {
      // Use the "Factory" to create an object instance.
      m_provided = Provided::Create(info.Env(), "my value");

   }
private:
   Provided m_provided;
   static Napi::FunctionReference constructor;
}