I use MQTT.js. Is it possible to define a different callback per topic?
For example, I subscribe to topics a
, b
, and c
and create an on message
callback per topic like so:
client.on('message', 'a', cb)
client.on('message', 'b', cb)
client.on('message', 'b', cb)
If not, how can I work this around?
No it is not possible.
You just need to add a if/else
or switch
block to your on message
callback that uses the topic as the selector.
e.g.
client.on('message', function(topic, message) {
switch(topic) {
case 'a':
...
break;
case 'b':
...
break;
default:
...
}
})
or store callback function in an object and use topics as the key e.g.
var callbacks = {}
callbacks["a"] = function(message) {...}
client.on('message', function(topic, message) {
callbacks[topic](message)
})