smartobject-watchify

An extension to make a smartobject instance listenable to its resource changes

1. Overview

This module is used make a smartobject instance able to listen to its resource changes, which could be helpful for creating a machine node responsive to any reosurce change within it.

2. Installation

$ npm install smartobject-watchify --save

3. Basic Usage

const SmartObject = require('@lwmqn/smartobject')
const soWatchify = require('@lwmqn/smartobject-watchify')

var so = new SmartObject()
so = soWatchify(so)

so.init('temperature', 0, { sensorValue: 31, units : 'C' })

// attach a listener to receive the change from resource 'temperature/0/sensorValue'
so.onChange('temperature/0/sensorValue', function (cVal, pVal) {
  console.log('A listener to this resource')
  console.log(cVal) // current value
  console.log(pVal) // previous value
})

so.onChange('temperature/0/sensorValue', function (cVal, pVal) {
  console.log('Another listener to this resource')
})

// Modify the sensorValue of the temperature sensor and the listener will be triggered
so.write('temperature', 0, 'sensorValue', 80, function (err, data) {
  if (err) console.log(err)
})

4. APIs

---

require('smartobject-watchify')(so)

smartobject-watchify exports a function that receives the smartobject instance as the parameter to be extended and returned.

Arguments:

1. so (Object): The instance of SmartObject class.

Returns:

• (Object) Watchified smartobject.

Examples:

const SmartObject = require('@lwmqn/smartobject')
const soWatchify = require('@lwmqn/smartobject-watchify')

const so = soWatchify(new SmartObject())

---

so.onChange(path, listener)

Attach a listener to observe a given resource for its change.

Arguments:

1. path (String): The path to the resource, e.g. 'humidity/6/sensorValue'.
2. listener (Function): function(cVal, pVal) {}, where cVal is the current value and pVal is the previous value before updated.

Returns:

• (none)

Examples:

so.onChange('temperature/3/sensorValue', function (cVal, pVal) {
  // Listen to 'temperature/3/sensorValue' for its change
})

---

so.onChangeOnce(path, listener)

Attach an one-time listener to observe a given resource for its change.

Arguments:

1. path (String): The path to the resource, e.g. 'humidity/6/sensorValue'.
2. listener (Function): function(cVal, pVal) {}, where cVal is the current value and pVal is the previous value before updated.

Returns:

• (Constructor) WatchifiedSmartObject

Examples:

so.onChangeOnce('presence/7/dInState', function (cVal, pVal) {
  // Listen to 'presence/7/dInState' only once for its change
})

---

so.removeListener(path, listener)

Remove a specified listener from listening to the given resource path.

Arguments:

1. path (String): The path to the resource, e.g. 'humidity/6/sensorValue'.
2. listener (Function): The listener function.

Returns:

• (none)

Examples:

var presenceListener = function (cVal, pVal) {
  // Listen to 'presence/7/dInState' only once for its change
}

// attach listener
so.onChange('presence/7/dInState', presenceListener)

// remove listener
so.removeListener('presence/7/dInState', presenceListener)

---

so.removeAllListeners(path)

Remove all listeners from listening to the given resource path.

Arguments:

1. path (String): The path to the resource, e.g. 'humidity/6/sensorValue'.

Returns:

• (none)

Examples:

so.removeAllListeners('temperature/0/sensorValue')

## License

Licensed under MIT.