I'm trying to initialize my node addon module using JS callback for logging. Initialize method is intended to store callback value for calling from other methods. So I add reference to the callback using napi_create_reference.
But when I'm trying to call the callback from my second addon method MyAddonMethod I receive napi_invalid_arg error.
I've tried to investigate the issue. The call to napi_typeof for the callback value from MyAddonMethod returns napi_invalid_arg too. Looks like the callback value was garbage collected despite my strong reference.
What am I doing wrong? Does napi_create_reference actually prevents callback object from being garbage collected between addon calls?
// JS side:
const addon = require('./addon.node');
function logCallbackFunction(logLine)
{
console.log("Trace: " + logLine);
}
addon.Initialize(logCallbackFunction);
addon.MyAddonMethod();
// C++ side
// Initialize method:
napi_ref ref;
napi_create_reference(env, value, 1, &ref);
g_Value = value; // store the value somewhere between calls
// MyAddonMethod method: // "env" doesn't change from call to call
napi_valuetype type;
napi_status stat = napi_typeof(env, g_Value, &type); // napi_invalid_arg
I've finally found what I was doing wrong. It is not eligible to store g_Value between calls. Instead napi_ref should be stored and napi_get_reference_value function used in order to extract the corresponded value. So the C++ side code should look like this:
// Initialize method:
napi_ref ref;
napi_create_reference(env, value, 1, &ref);
g_Ref = ref; // store the reference somewhere between calls
// MyAddonMethod method:
napi_value referenceValue;
napi_get_reference_value(env, g_Ref, &referenceValue);
napi_valuetype type;
napi_status stat = napi_typeof(env, referenceValue, &type); // napi_ok, napi_function
Of course you should not forget to release the reference using napi_delete_reference when it is not needed anymore.