TypeError: instance[method].bind is not a function AdonisJs

Question

I am integrating MQTT-adonis module adonis-mqtt respo on git here in adonis-js application while serving it throws an exception

TypeError: instance[method].bind is not a function

Can any one guide why this is appearing.

//event.js

'use strict'
 const Event = use('Event');
const Mqtt = use('Mqtt');
// Listen to some Events of the library
Event.on('MQTT:Connected', 'Message.subscription')
Event.on('MQTT:Disconnected', 'Message.disconnected')

//Listeners/Message.js

class Message extends MqttListener {

get subscription () {
return 'Topic/Info'
 }

async handleMessage (message, wildcardMatches) {
  }

it appears that it is throwing exception here in this block

//node_modules/adonis-mqtt/Mqtt/Mqtt.js

this.client.on('connect', this._handleConnect.bind(this)) //here at this line
    this.client.on('offline', this._handleDisconnect.bind(this))
    this.client.on('close', this._handleDisconnect.bind(this))
    this.client.on('end', this._handleDisconnect.bind(this))
    this.client.on('message', this._handleMessage.bind(this))

EDIT:::

How to reproduce this:

pre-requisite:

• Node JS latest version (here)
• Adonis Js latest versions (here)

clone this:

• https://github.com/Q930844N/mqtt-adonis-test

• move to directory path

• npm install
• adonis serve --dev

Update:

while removing get from subscription function, it works with no error, but I am unable to get the required data in following code snippet

//node_modules/adonis-mqtt/Mqtt/Mqtt.js

async _registerListener (file) {
    const filePath = path.join(this.listenersPath, file)
    let task
    try {
      task = require(filePath)
    } catch (e) {
      if (e instanceof ReferenceError) {
        debug(
          'Unable to import task class <%s>. Is it a valid javascript class?',
          file)
        return
      } else {
        throw e
      }
    }

    // Get instance of task class
    const taskInstance = ioc.make(task)
    if (!taskInstance.subscription || taskInstance.subscription === '') {
      console.error(`MqttListener ${file} does not have a subscription string!`)
    } else {
      this.client.subscribe(taskInstance.subscription) // here
      debug('Subscribed to topic %s', taskInstance.subscription)
      console.log('Subscribed to topic %s', taskInstance.subscription)
      this.listeners.push(taskInstance)
    }
  }

Update: 2

There are two folders in app one is Listeners and other is MqttListeners, thse both have same named file Test.js, it is also forcing to keep both files. However changes in file exist in Listener folder doesnt make any impact. However removing get prefix from subscription function and console messages in handleMessage() from MqttListners folder's file is seems to be perfect. Receiving published topics info

Answer 1

Your problems is here

// events.js
Event.on('MQTT:Connected', 'Message.subscription')

By this, you're binding Message.subscription method to MQTT:Connected event (actually, this happens in node_modules/@adonisjs/fold/src/Ioc/index.js#L879).

However, your Message.subscription is not a normal function but getter. You cannot bind getters because this method syntax doesn't use function expressions.

So, in order to fix your problem you should either bind MQTT:Connected event to some other method i.e.

// events.js
Event.on('MQTT:Connected', 'Message.connection')

// Listeners/Message.js
class Message extends MqttListener {
  connection() {
     return 'test/#';
  }
}

or simply remove get prefix from your subscription method

// Listeners/Message.js
class Message extends MqttListener {

  subscription () {
    return 'test/#';
  }
}

Please let me know if my answer is not clear enough or you need some additional information.

UPDATE: See some proof that it works