How can I send a C++ String to node.js?

Question

Im very new to making C++ addons for node.js

So my Question is: Is there a way for an addon-function to return a String? And if so, How? Further Explaining:

Lets say i have a string called std::string testString in my C++ Source File. When given following JS code:

const myAddon = require('path'); console.log(myAddon.myFunc());

It should output the data testString holds.

Sorry if something isnt understandable, this is my first Question here.

Edit: const char* myChar = "Hello World"; would also be okay. Top Priority is to send any kind of Text.

Does this answer your question? How do I use std::string in a C++ Addon for Node.js? — Botje
– Botje, Commented Aug 10, 2020 at 19:11
@Botje it kind of helped, but i want to understand how it works too. So a Simple Showcase of Logging the ancient "Hello World" to the console would be the best. Still thanks for the afford of replying :) Edit: The If Statements and other functions used there confuse me what is actually needed, and what is only there bc of the Question-Authors Goal. Thats the Point im trying to make — PersonWhoLikesCPP
– PersonWhoLikesCPP, Commented Aug 11, 2020 at 7:51
Returning a string from a function in a C++ addon is the hello world in the documentation. Did you try following that? What did not work? — Botje
– Botje, Commented Aug 11, 2020 at 8:03
@Botje Logging Text as const char* does work perfectly fine: args.GetReturnValue().Set(String::NewFromUtf8(isolate, myChar).ToLocalChecked()); where myChar is type const char*. Doing this directly with std::string doesnt work ofcourse. But atleast i can now send text to my js file, Thanks! — PersonWhoLikesCPP
– PersonWhoLikesCPP, Commented Aug 11, 2020 at 8:22
See std::string::c_str() to get a const char * out of a std::string — Botje
– Botje, Commented Aug 11, 2020 at 8:24

Botje · Accepted Answer · 2020-08-11 08:29:34Z

0

Here is an adapted version of the hello world example in the documentation:

#include <node.h>
#include <string>

namespace demo {

using v8::FunctionCallbackInfo;
using v8::Isolate;
using v8::Local;
using v8::Object;
using v8::String;
using v8::Value;

std::string testString; // value is set elsewhere.

void MyFunc(const FunctionCallbackInfo<Value>& args) {
  Isolate* isolate = args.GetIsolate();
  args.GetReturnValue().Set(String::NewFromUtf8(
      isolate, testString.c_str()).ToLocalChecked());
}

void Initialize(Local<Object> exports) {
  // this would be a good spot to set testString
  NODE_SET_METHOD(exports, "myFunc", MyFunc);
}

NODE_MODULE(NODE_GYP_MODULE_NAME, Initialize)

}

answered Aug 11, 2020 at 8:29

Botje

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