在Node.js C ++ Addon中发出一个事件
我有一个从工业控制器读取过程数据的应用程序。 我想把这些数据推送到一个网页上。 为此，我在c ++中编写了一个node.js插件，用于扫描进程数据，并在数据值更改时尝试触发事件。 一切工作正常的插件，直到它试图触发一个事件，在这一点node.js终止与错误：
undefined:0 TypeError: undefined is not a function 下面是CPP，javascript shim和testingjavascript。 任何见解都非常感谢。
提前致谢。
node_corelink.cpp
typedef struct CoreLinkValue { // pointer to a CTS variant value CtsVariant* value; // copy of the last value that was broadcast CtsVariant lastValue; } CoreLinkValue; // // An event structure for pushing events to node.js // Requires the javascript shim code in node_corelink.js // struct Emitter: ObjectWrap { static Handle<Value> New(const Arguments& args); static Handle<Value> DataChange(const char* topic, CtsVariant* value); }; // // Create a message payload based on the variant type and // initiate sending out on the topic // static Handle<Value> createVariantHandle(CtsVariant* value) { Handle<Value> ret; switch (value->type) { case CTSTYPE_BIT: case CTSTYPE_BYTE: ret = Integer::New(value->value.byte[0]); break; case CTSTYPE_WORD: ret = Integer::New(value->value.word[0]); break; case CTSTYPE_DWORD: ret = Integer::New(value->value.dword[0]); break; case CTSTYPE_WORD64: ret = Number::New(value->value.word64); break; case CTSTYPE_REAL64: ret = Number::New(value->value.real64); break; default: ret = Undefined(); break; } return ret; } Handle<Value> Emitter::New(const Arguments& args) { HandleScope scope; assert(args.IsConstructCall()); Emitter* self = new Emitter(); self->Wrap(args.This()); return scope.Close(args.This()); } // emits DataChange Event Handle<Value> Emitter::DataChange( const char* topic, CtsVariant* value ) { HandleScope scope; Handle<Value> argv[3] = { String::New("DataChange"), // event name String::New(topic), // topic argument createVariantHandle(value) // value argument }; printf ("C++ Emitting event!\n" ); MakeCallback(context_obj_, "emit", 2, argv); return True(); } // // Triggered by the event loop on a regular interval. // Scans the registered data to see if the latest value has been // broadcast and does so if needed. // void scan_task( uv_timer_t* timer, int status ) { std::map<std::string, CoreLinkValue>::iterator it; bool doUpdate; for( it = pdos_.begin(); it != pdos_.end(); ++it ) { if (forceRefreshPdos_ == true) { // // An update of this value was requested. // doUpdate = true; } else if ( it->second.value->type != it->second.lastValue.type ) { // // If the types don't match, then this variant was obviously // updated. // doUpdate = true; } else if ( it->second.value->value.word64 != it->second.lastValue.value.word64 ) { // // Word64 contains all bits of the value. If this value has // changed, then they've all changed. // doUpdate = true; } else { doUpdate = false; } if (doUpdate) { it->second.lastValue.value = it->second.value->value; Emitter::DataChange( it->first.c_str(), it->second.value ); } } if (forceRefreshPdos_) { forceRefreshPdos_ = false; printf("Completed refresh all.\n"); } } // // Start the execution of the scan loop // int startScanLoop( void ) { uv_timer_init( uv_default_loop(), &scanTimer_ ); uv_timer_start( &scanTimer_, // timer instance &scan_task, // callback function 0, // startup delay (ms) 100 ); // repeat interval (ms) return 1; } // // Stop the execution of the scan loop // void stopScanLoop( void ) { uv_timer_stop( &scanTimer_ ); } // // Connects to the kernel IPC // Handle<Value> connect(const Arguments& args) { HandleScope scope; ... startScanLoop(); return scope.Close( True() ); } // // Shuts down the kernel IPC // Handle<Value> close(const Arguments& args) { HandleScope scope; stopScanLoop(); ... return scope.Close( True() ); } // // Called by node.js to initialize the library. // void init(Handle<Object> target) { target->Set(String::NewSymbol("connect"), FunctionTemplate::New(connect)->GetFunction()); target->Set(String::NewSymbol("close"), FunctionTemplate::New(close)->GetFunction()); // // Events interface // Local<FunctionTemplate> t = FunctionTemplate::New(Emitter::New); t->InstanceTemplate()->SetInternalFieldCount(1); t->SetClassName(String::New("Emitter")); target->Set(String::NewSymbol("Emitter"), t->GetFunction()); } NODE_MODULE(node_corelink, init)
node_corelink.js
module.exports = require(__dirname + '/build/Release/node_corelink.node'); var Emitter = require(__dirname + '/build/Release/node_corelink.node').Emitter; var events = require('events'); inherits(Emitter, events.EventEmitter); exports.Emitter = Emitter; // extend prototype function inherits(target, source) { for (var k in source.prototype) target.prototype[k] = source.prototype[k]; }
test.js
process.stdin.resume(); //so the program will not close instantly process.on('exit', function () { corelink.close(); console.log('Goodbye!'); }); process.on('SIGINT', function () { console.log('Got SIGINT.'); process.exit(); }); var corelink = require('./node_corelink'); var Emitter = require('./node_corelink').Emitter; var e = new Emitter(); e.on('DataChange', function(s) { console.log('DataChange'); }); corelink.connect();
我能够以不太优雅的方式触发callback。
node_corelink.js
module.exports = require(__dirname + '/build/Release/node_corelink.node');
test.js
var corelink = require('./node_corelink'); function onDataChange( topic, value ) { if ( value !== undefined ) console.log ( topic + " ::: " + value.toString() ); } function onMessage( msg ) { console.log ( "Message from kernel: " + msg.toString() ); } corelink.connect(onDataChange, onMessage);
node_corelink.cpp
static void dataChange( const char* topic, CtsVariant* value ) { HandleScope scope; Handle<Value> argv[2] = { String::New(topic), // topic argument createVariantHandle(value) // value argument }; MakeCallback(Context::GetCurrent()->Global(), pfOnDataChange_, 2, argv); } static void onMessage( const char* message ) { HandleScope scope; Handle<Value> argv[1] = { String::New(message) // message argument }; MakeCallback(Context::GetCurrent()->Global(), pfOnMessage_, 1, argv); } // // Connects to the kernel IPC // Handle<Value> connect(const Arguments& args) { HandleScope scope; if ( args.Length() < 2 || !args[0]->IsFunction() || !args[1]->IsFunction() ) { return scope.Close( False() ); } pfOnDataChange_ = Persistent<Function>::New(args[0].As<Function>()); pfOnMessage_ = Persistent<Function>::New(args[1].As<Function>()); ... return scope.Close( True() ); }