Sync

[Deleted user]

Hi, I've got an issue with an asynchronous function where i'm using sql requests.

function get_user_message_list(parameters, array, response)
{
    var new_array = [];
    for (var i in array) {
        //console.log(i);
        //console.log(array[i]);

        var json = array[i];

        json = get_json_message(parameters, json);

        console.log(json);
        new_array.push(json);
        console.log(new_array);
    }

    console.log("NEW ARRAY :");
    console.log(new_array);

    response.writeHeader(200, {'Content-Type':'application/json'});
    response.end(JSON.stringify(new_array));
}

function get_json_message(parameters, json)
{
    console.log("JSON OBJECT :");
    console.log(json);
    var dataset = db.from(TABLES.USER).join(TABLES.MOVIE_LIST, {MLUserId: sql.URId}).join(TABLES.MOVIE, {MVId: sql.MLMovieId});

    dataset.where('MLSeen={seen} AND MVSourceId={movie} AND MVSource={source} AND URId!={user}', {seen: 1, movie: json['content']['movie_id'], source: json['content']['movie_source'], user:parameters.FACEBOOK_ID}).all().then(function(users){
        if (users) {
            for (var j in users) {
                json['content']['users_seen'].push(users[j].URId);
            }
        }

        //console.log(json['content']['users_seen']);

        dataset.where('MLSeen={seen} AND MVSourceId={movie} AND MVSource={source} AND URId!={user}', {seen: 0, movie: json['content']['movie_id'], source: json['content']['movie_source'], user:parameters.FACEBOOK_ID}).all().then(function(users){
            if (users) {
                for (var j in users) {
                    json['content']['users_not_seen'].push(users[j].URId);
                }
            }

            console.log(json);
        }, errorHandler);
    }, errorHandler);
}

With this code, I want to wait the sql requests and then push the json to my array and after send the response to the client!
How can I achieve this ?

[Doug Martin]

Hi, the way I would do it would be to do something like the following.

//see http://pollenware.github.com/comb/index.html
var comb = require("comb"),
    when = comb.when,
    Promise = comb.Promise,
    PromiseList = comb.PromiseList;
var get_json_message = function (parameters, json) {
    var content = json.content;
    var dataset = db
        .from(TABLES.USER)
        .join(TABLES.MOVIE_LIST, {MLUserId:sql.URId})
        .join(TABLES.MOVIE, {MVId:sql.MLMovieId})
        //create the dataset only once this will be more efficient
        .where({MVSourceId:content.movie_id, MVSource:content.movie_source, URId:parameters.FACEBOOK_ID});

    //create a promise to return
    var ret = new comb.Promise();
    when(
        dataset.where({MLSeen:0}).selectMap("URId"),
        dataset.where({MLSeen:1}).selectMap("URId")
    ).then(function (res) {
            content.users_seen = content.users_seen.concat(res[0]);
            content.users_not_seen = content.users_not_seen.concat(res[0]);
            ret.callback(json);
        }, ret); //notice how I pass ret back into the .then call this acts as an errback

};

var get_user_message_list = function (parameters, array, response) {

    new PromiseList(array.map(function (json) {
        return get_json_message(parameters, json);
    })).then(function () {
            response.writeHeader(200, {'Content-Type':'application/json'});
            //when working with objects it is all passby reference so copying the values over to the new array
            //is pointless unless you return a new object
            response.end(JSON.stringify(array));
        }, errorHandler);
}

[Deleted user]

Thank you for you help !! I'm a beginner in the world of JavaScript and async function so it's really hard for me :/