Question

我已经很好地补充了MQTT，但是我遇到execute()方法的问题。除此之外，所有其他功能（unsubscribe）都可以正常工作。我已经检查了拼写，甚至完成了mqttCon.publish() , mqttCon.subscribe(), mqttCon.on()...，并将其带到库实现中，这意味着它是正确的方法，并得到了很好的引用，但我仍然在下面得到错误。我该怎么解决？

此行： ctrl +click

mqttCon.unsubscribe(topic)

注意：我正在使用ES6（Emacscript 6+）javascript和不是打字稿。 Nodejs TypeError: mqttCon.unsubscribe is not a function at noopHandler (/home/dev/project-dir/src/mqtt/processMessage.js:5:13) at module.exports (/home/dev/project-dir/src/mqtt/processMessage.js:10:20) at MqttClient.client.on (/home/dev/project-dir/src/mqtt/mqttCon.js:16:13) at MqttClient.emit (events.js:189:13) at MqttClient._handlePublish (/home/dev/project-dir/node_modules/mqtt/lib/client.js:1271:12) at MqttClient._handlePacket (/home/dev/project-dir/node_modules/mqtt/lib/client.js:410:12) at work (/home/dev/project-dir/node_modules/mqtt/lib/client.js:321:12) at Writable.writable._write (/home/dev/project-dir/node_modules/mqtt/lib/client.js:335:5) at doWrite (/home/dev/project-dir/node_modules/mqtt/node_modules/readable-stream/lib/_stream_writable.js:428:64) at writeOrBuffer (/home/dev/project-dir/node_modules/mqtt/node_modules/readable-stream/lib/_stream_writable.js:417:5)和npm 12.18.1

这是我的连接代码6.14.6：

mqttCon.js

这是const mqtt = require('mqtt') const processMessage = require('./processMessage') const logger = require('../logConf') const options = { host: '', port: '', username:'', password: '', protocol: '' }; const client = mqtt.connect(options) client.on("connect", function () { console.log("MQTT connected with status: " + client.connected); if (client.connected) { client.on('message', (topic, message) => { processMessage(topic, String(message)) }) } }) client.on('error', error => { console.log(error,'ERROR') logger.errorLogger.error(error) }) client.on('reconnect', error => { console.log(error,'RECONNECT') logger.errorLogger.error(error) }) client.on('close', error => { console.log(error,'CLOSE') logger.errorLogger.error(error) }) client.on('disconnect', error => { console.log(error,'DISCONNECT') logger.errorLogger.error(error) }) client.on('offline', error => { console.log(error,'OFFLINE') logger.errorLogger.error(error) }) module.exports = client：

processMessage.js

Answer 1

您的mqttCon.js文件没有client.prototype.unsubscribe = function() {}，因此错误是正确的。您正在将client定义为模块，但是实际上您需要在某个地方调用mqtt.unsubscribe()。因此，您需要在unsubscribe()常量中添加client函数（在这种情况下，它实际上应该是var），或者在需要mqtt之后调用mqtt.unsubscribe()函数您的processMessage.js文件中的模块...。我认为这与您尝试执行的操作背道而驰。您可能需要阅读更多有关module.exports实际工作原理的信息：https://www.sitepoint.com/understanding-module-exports-exports-node-js/

更新：上面的内容影响了我的想法，问题是我正在导入processMessage.js，而这反过来又导入了导入mqttCon.js。循环导入，意味着mqttCon（mqttClient）始终尚未在processMessage.js内部初始化。解决方案是，当客户端已经初始化并导出为以下模块时，我将processMessage.js导入了client.on('connect'....)...块中：


client.on("connect", () => {
    console.log("MQTT connected  with status: " + client.connected);
    if (client.connected) {
        client.on('message', (topic, message) => {
            require('./processMessage')(topic, String(message))
        })
    }
})

Node.js MQTT：退订不是功能

1 个答案: