Exploring the idea of calling a Node.js callback from within my asynchronous addon function has been an interesting journey. I found inspiration in both synchronous (here) and asynchronous (here) examples to guide me.
However, encountering a Segmentation fault when trying to execute a callback provided to the C++ AsyncWorker child class was quite a challenge.
This is the essence of my code:
#include <nan.h>
#include <functional>
#include <iostream>
#include <exception>
using namespace Nan;
using namespace v8;
using namespace std;
class ScriptWorker : public AsyncWorker {
public:
ScriptWorker(Callback *callback, const std::map<std::string, Callback*>)
: AsyncWorker(callback), script(script), cbs(cbs) {}
~ScriptWorker() {}
void Execute () {
// ------------------------
// Segmentation fault after
// ------------------------
Local<Value> argv[] = {
New<v8::Number>(id)
};
// -------------------------
// Segmentation fault before
// -------------------------
cbs["getUser"]->Call(1, argv);
}
private:
std::string script;
std::map<std::string, Callback*> cbs;
};
NAN_METHOD(Method) {
Local<Object> array = info[0]->ToObject();
Callback *callback = new Callback(info[1].As<Function>());
// Building up callbacks passed in from JavaScript.
// Initially focusing on the "getUser" example.
std::map<std::string, Callback*> cbs;
cbs.insert(std::pair<std::string, Callback*>("getUser",
new Callback(
array->Get(
v8::String::NewFromUtf8(v8::Isolate::GetCurrent(), "getUser")
).As<Function>()
)
));
AsyncQueueWorker(new ScriptWorker(callback, cbs));
}
NAN_MODULE_INIT(Init) {
Nan::Set(target, Nan::New<String>("hello").ToLocalChecked(), Nan::GetFunction(Nan::New<FunctionTemplate>(Method)).ToLocalChecked());
}
NODE_MODULE(hello, Init)
I have a couple of questions lingering in my mind:
- Is it advisable to forego using Nan's AsyncWorker and craft my own solution instead?
- What steps are necessary to configure the Execute function for calling into JavaScript successfully?