Haha, no problem. Maybe I gave you the hard version a little bit too soon.
1. I don't have a full understanding of how your application works as a
whole, but as I understood you can in fact call getLightsIds and upon
getting the result, calling initLightState with that result.
2. Yes, reduce is pretty much a forEach in this case. You can refactor
this part to something you like more very safely.
3. tasks is an object assigning an asynchronous task to each id. so it's
in fact something like {'my-first-lamp': function (callback) {...}} and so
on. It is an object for which every field is a function describing how to
get a result for that particuliar field. This is probably unclear, which
leads me to the next point
4. async.parallel does exactly what is said here
(https://github.com/caolan/async#parallel). It takes several asynchronous
tasks, executes them all in parallel and calls its own callback with an
aggregation of the results of all the tasks
5. lastKnownStates in my code is empty, and it's a mistake! sorry.
lastKnownState is meant to be the last states of your lamps that you
notified your client with. So you should probably update it when you notify
your clients =)
Hope this helps.
On Friday, 4 April 2014 14:35:38 UTC+2, JL wrote:
>
> 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.
>>>
>>
--
--
Job Board: http://jobs.nodejs.org/
Posting guidelines:
https://github.com/joyent/node/wiki/Mailing-List-Posting-Guidelines
You received this message because you are subscribed to the Google
Groups "nodejs" group.
To post to this group, send email to [email protected]
To unsubscribe from this group, send email to
[email protected]
For more options, visit this group at
http://groups.google.com/group/nodejs?hl=en?hl=en
---
You received this message because you are subscribed to the Google Groups
"nodejs" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
For more options, visit https://groups.google.com/d/optout.
