Hello,
First, thanks A LOT for taking the time to help me.. i appreciate it !
I really tried your way, but my head hurts :p
Could you please comment more the example you provided ?
Here's what i don't understand :
1. First, your initLightState should be in my getLightsId function so i
can pass my array of Ids in it ?
2. the ids.reduce is like ids.forEach() ?
3. if i understand the tasks[id] = getLightState.bind(id); is making
an array (tasks) that contains my lights state ?
4. I dont get what async.parallel does
5. lastKnownStates in your code is empty, when should i fill it ?
I am sorry for all my question, i really have trouble understanding how it
works..
Thank you for your time.
Le vendredi 4 avril 2014 11:06:06 UTC+2, Floby a écrit :
>
> 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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