在尝试检索时,通过nan传递数组返回未定义

我目前正在使用他们的c ++ / v8系统为NodeJS编写一个本地插件,并试图从Javascript写入一个数组到C ++,然后再检索它。 每当我尝试从数组中检索一个值并将其返回时,它将返回一个空数组 – 正如我最近潜入c ++中,我不确定这是我的误解指针/ c ++基础或NodeJS c ++交互。

我的档案如下:

functions.cc

#include "functions.h" #include <node.h> #include <nan.h> using namespace std; using namespace v8; NAN_METHOD(nothing) { } NAN_METHOD(aString) { info.GetReturnValue().Set(Nan::New("This is a thing.").ToLocalChecked()); } NAN_METHOD(aBoolean) { info.GetReturnValue().Set(false); } NAN_METHOD(aNumber) { info.GetReturnValue().Set(1.75); } NAN_METHOD(anObject) { v8::Local<v8::Object> obj = Nan::New<v8::Object>(); Nan::Set(obj, Nan::New("key").ToLocalChecked(), Nan::New("value").ToLocalChecked()); info.GetReturnValue().Set(obj); } NAN_METHOD(anArray) { v8::Local<v8::Array> arr = Nan::New<v8::Array>(3); Nan::Set(arr, 0, Nan::New(1)); Nan::Set(arr, 1, Nan::New(2)); Nan::Set(arr, 2, Nan::New(3)); info.GetReturnValue().Set(arr); } NAN_METHOD(callback) { v8::Local<v8::Function> callbackHandle = info[0].As<v8::Function>(); Nan::MakeCallback(Nan::GetCurrentContext()->Global(), callbackHandle, 0, 0); } // Wrapper Impl Nan::Persistent<v8::Function> MyObject::constructor; NAN_MODULE_INIT(MyObject::Init) { v8::Local<v8::FunctionTemplate> tpl = Nan::New<v8::FunctionTemplate>(New); tpl->SetClassName(Nan::New("MyObject").ToLocalChecked()); tpl->InstanceTemplate()->SetInternalFieldCount(1); //Nan::SetPrototypeMethod(tpl, "plusOne", PlusOne); Nan::SetPrototypeMethod(tpl, "getArr", arrY); Nan::SetPrototypeMethod(tpl, "PassArray", passArray); Nan::SetPrototypeMethod(tpl, "setArray", SetArray); constructor.Reset(Nan::GetFunction(tpl).ToLocalChecked()); Nan::Set(target, Nan::New("MyObject").ToLocalChecked(), Nan::GetFunction(tpl).ToLocalChecked()); } MyObject::MyObject(v8::Local<v8::Array> value) : value_(value) { } MyObject::~MyObject() { } NAN_METHOD(MyObject::New) { if (info.IsConstructCall()) { v8::Local<v8::Array> arr = Nan::New<v8::Array>(); v8::Local<v8::Array> value = v8::Handle<v8::Array>::Cast(arr); MyObject *obj = new MyObject(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(cons->NewInstance(argc, argv)); } } // NAN_METHOD(MyObject::PlusOne) { // MyObject* obj = Nan::ObjectWrap::Unwrap<MyObject>(info.This()); // obj->value_ += 1; // info.GetReturnValue().Set(obj->value_); // } NAN_METHOD(MyObject::SetArray){ Nan::HandleScope scope; vector<string> result; Handle<Value> val; Local<Array> arr = Nan::New<Array>(); MyObject* obj = ObjectWrap::Unwrap<MyObject>(info.Holder()); if (info[0]->IsArray()) { Handle<Array> jsArray = Handle<Array>::Cast(info[0]); for (unsigned int i = 0; i < jsArray->Length(); i++) { val = jsArray->Get(i); result.push_back(string(*String::Utf8Value(val))); Nan::Set(arr, i, val); } } info.GetReturnValue().Set(obj->value_); } NAN_METHOD(MyObject::arrY){ MyObject* obj = ObjectWrap::Unwrap<MyObject>(info.Holder()); info.GetReturnValue().Set(Local<Array>::Cast(obj->value_)); } NAN_METHOD(MyObject::passArray) { Nan::HandleScope scope; vector<string> result; Handle<Value> val; Local<Array> arr = Nan::New<Array>(); if (info[0]->IsArray()) { Handle<Array> jsArray = Handle<Array>::Cast(info[0]); for (unsigned int i = 0; i < jsArray->Length(); i++) { val = jsArray->Get(i); result.push_back(string(*String::Utf8Value(val))); Nan::Set(arr, i, val); } } MyObject* obj = Nan::ObjectWrap::Unwrap<MyObject>(info.This()); obj->value_ = arr; info.GetReturnValue().Set(obj->value_); } 

functions.h

 #ifndef NATIVE_EXTENSION_GRAB_H #define NATIVE_EXTENSION_GRAB_H #include <nan.h> // Example top-level functions. These functions demonstrate how to return various js types. // Implementations are in functions.cc NAN_METHOD(nothing); NAN_METHOD(aString); NAN_METHOD(aBoolean); NAN_METHOD(aNumber); NAN_METHOD(anObject); NAN_METHOD(anArray); NAN_METHOD(callback); // Example with node ObjectWrap // Based on https://nodejs.org/api/addons.html#addons_wrapping_c_objects but using NAN class MyObject : public Nan::ObjectWrap { public: static NAN_MODULE_INIT(Init); private: explicit MyObject(v8::Local<v8::Array> value); ~MyObject(); static NAN_METHOD(New); static NAN_METHOD(PlusOne); static NAN_METHOD(SetArray); static NAN_METHOD(arrY); static NAN_METHOD(passArray); static Nan::Persistent<v8::Function> constructor; v8::Local<v8::Array> value_; }; #endif 

index.js

 var NativeExtension = require('bindings')('NativeExtension'); module.exports = NativeExtension; console.log(NativeExtension.aString()); var obj = NativeExtension.MyObject([1,2,3]); console.log(NativeExtension.aString()); console.log(obj.PassArray([1, 1, 3])); console.log(obj.getArr()); console.log(obj.setArray()) 

出于testing的目的,代码绝对不是干的,它是基于github提供的nan-boilerplate代码的非剥离版本,可以在这里find 。

重读我自己的代码时,我可以肯定地告诉我的方法命名是不好的 ,所以PassArr应该设置一个数组,并且getArr应该返回由“PassArr”传递的数组。 SetArray是我留下的一个骇人的尝试。

重申一下,我试图实现的function是:

 Javascript Array -> C++ variable C++ variable -> Javascript Array 

但目前的function不会持久我的variables。 运行index.js的结果如下:

 This is a thing. This is a thing. [ 1, 1, 3 ] Console { log: [Function: bound ], info: [Function: bound ], warn: [Function: bound ], error: [Function: bound ], dir: [Function: bound ], time: [Function: bound ], timeEnd: [Function: bound ], trace: [Function: bound trace], assert: [Function: bound ], Console: [Function: Console] } [] 

       

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