Hello, this seems like a fairly well addressed use case. You're not so far !
First of all, I strongly suggest you stick to the convention of error first
callbacks. Believe me it will help you use other tools and interoperate
them with your code.
The principle is simple : whenever a method/function is asynchronous
- it takes a callback as last argument
- when an error occurs during that operation, it calls the callback with
an error as first argument
- when successful, it calls the callback with null as first argument and
the result as second argument
If you can change your methods to follow this pattern, then you'll be able
to use the async [1] module directly to handle your aggregation of several
asynchronous results.
If you want to trigger events only if the state of the lamps have changed,
you could use something like deep-equal [2] to compare results over time.
In the end, you should be able to write something like this
var deepEqual = require('deep-equal');var async = require('async');
function initLightState (ids, callback) {
var lastKnownStates = {}; // initialise to empty array
var tasks = ids.reduce(function (tasks, id) {
tasks[id] = getLightState.bind(id);
// If you want to use less magic
// the following is strictly equivalent
tasks[id] = function (callback) {
getLightState(id, callback);
}
return tasks;
} {});
// checking states every 500 ms
return setInterval(checkState, 500);
function checkState () {
async.parallel(tasks, function (err, states) {
if(!deepEqual(states, lastKnownStates)) {
notifyClient(states);
}
});
};}
[1] https://www.npmjs.org/package/async
[2] https://www.npmjs.org/package/deep-equal
On Thursday, 3 April 2014 20:13:38 UTC+2, JL wrote:
>
> Hello everyone,
>
> I am learning javascript and nodejs, im currently making an nodejs app to
> manage my philips hue lamps.
>
> And i am struggling with the asynchronous and callbacks.
>
> First let me explain what i want to achieve.
>
> I have a function that get the id of all my lights, named getLightsId :
>
> function getLightsId(callback){
> args ={
> path:{"username":"username"}
> };
>
> client.registerMethod("getLightState",
> "bridge_adress/api/${username}/lights/", "GET");
>
> client.methods.getLightState(args, function(data,response){
> var id = [];
> for(key in data){
> id.push(key);
> }
> callback(id);
> });}
>
> Then i have a function getLightState that get the state of a specific lamp
> determined by its id
>
> function getLightState(id, callback){
>
> args ={
> path:{"username":"username", "id":id}
> };
>
> client.registerMethod("getLightState",
> "http://bridge_address/api/${username}/lights/${id}";, "GET");
>
> client.methods.getLightState(args, function(data,response){
> callback(data);
> });}
>
> And finally i have a function initLightsState that send the state of all
> the lights in an object to my client. be prepared to see ugly shit :p, its
> pretty dirty, but hey, it works (kinda).
>
> function initLightsState(callback){
>
> getLightsId(function(idArray) {
>
> var lightsState = new Object();
>
> idArray.forEach(function(id) {
>
> setInterval(function(){getLightState(id, function(state) {
>
> lightsState[id] = state;
> });},500);
> });
>
> callback(lightsState);
> io.sockets.on('connection', function (socket) {
> setInterval(function(){
> socket.emit('updateLightsState', lightsState);
> },500);
> });
> });}
>
> I had to put a setInterval() to my getLightState function because
> otherwise it was always sending me the same object with the same data, i
> know its dirty but i couldnt find another way.
>
> then i emit also with a setInterval() my object to my client.
>
> The problem is that its obviously spamming my client with the state of my
> lights.. it works, but its very far from being the cleanest way to do this.
>
> What i want to do, is to compare server-side the previous state of my
> light with the current one, and only if its different send it to the client.
>
> But im stuck with the callback and everything and cant get it work.
>
> Could someone please show me the simplest way to do this ?
>
> Thanks a lot.
>
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