node js callback from native C++ code is throwing errors - c++

Question

I am trying to implement event listeners. Node js will subscribe to the events (using C++ function). When the event occurs, C++ should inform node js.
JS code:
pal.subscribeEvent("ONSTATECHANGE", function(a) { console.log("Event received for ONSTATECHAN";});
function kcb (a) {
console.log("KCB .....ONSTATECHAN"+JSON.stringify(a));
}
pal.subscribeEvent("ONSTATECHANGE", kcb);
C++ code:
struct deviceNapi {
Napi::Env env; // to store JS Function Env
Napi::Function jsCallback; // to Store JS function
};
//std::multimap<int, Napi::Function> deviceEventMgmt;
std::multimap<int, struct deviceNapi> deviceEventMgmt;
Napi::Value PAL::subscribeEvent(const Napi::CallbackInfo& info) {
Napi::Env env = info.Env();
int eventID = info[0].As<Napi::Number>().Int32Value();
deviceNapi obj;
obj.env = env;
obj.jsCallback = info[1].As<Napi::Function>();
deviceEventMgmt.insert(std::make_pair(eventID, obj));
/*Napi::Function jsCallback = info[1].As<Napi::Function>();
deviceEventMgmt.insert(std::make_pair(eventID, jsCallback));*/
}
void ProcessDeviceEvent(int evt, DeviceEvtData data) {
switch(evt) {
case ONSTATECHANGE:
for(auto it = deviceEventMgmt.begin(); it != deviceEventMgmt.end(); it ++) {
if(it->first == ENUM_VERIZON_DEVICE_PENDING_RESET) {
Napi::Env env = it.second.env;
Napi::Object ret = Napi::Object::New(env);
ret.Set("reason", Napi::String::New(env, data.resetReason));
ret.Set("time", Napi::Number::New(env, data.seconds));
it->second.jsCallback.Call(ret);
}
}
/*for(auto it = deviceEventMgmt.begin(); it != deviceEventMgmt.end(); it ++) {
if(it->first == ENUM_VERIZON_DEVICE_PENDING_RESET) {
it->second.Call();
}
}*/
break;
default:
std::cout << "ProcessDeviceEvent : Currently not handling evt : " << evt << std::endl;
break;
}
}
C++ code is throwing below errors while compiling
../PAL.cpp: In member function 'Napi::Value PAL:: subscribeEvent(const Napi::CallbackInfo&)':
../PAL.cpp:1915:13: error: use of deleted function 'deviceNapi::deviceNapi()'
deviceNapi obj;
^~~
../PAL.cpp:1903:8: note: 'deviceNapi::deviceNapi()' is implicitly deleted because the default definition would be ill-formed:
struct deviceNapi {
^~~~~~~~~~
../PAL.cpp:1903:8: error: no matching function for call to 'Napi::Env::Env()'
Can any one please help me to how to fix this problem of storing Node function env into C++ map. I need to save the env so that I can send the response when calling Node callback.

Answer 1

Napi::Env doesn't have a default constructor so your deviceNapi struct's default constructor cannot initialise the env member so the compiler didn't generate it, but you try to call it on this line:
deviceNapi obj;
You can fix this by initialising it like this:
deviceNapi obj = {env, info[1].As<Napi::Function>()};