Local array not being pushed to - javascript

I have the following code. The array prices does not seem to be pushed to the prices array despite successfully retrieving the ustock.unitprice.
getLatestMarketPrices: function(username, callback) {
var prices = [];
db.find('portfolio', {user: username}, function(err, stocks) {
for(var i = 0; i < stocks.length; i++) {
module.exports.getQuote(stocks[i].stock, function(err, ustock) {
console.log(ustock.unitprice); // Retrieves 1.092
prices.push(ustock.unitprice); // Should push to prices array?
});
}
console.log(prices); // Prices is still [] despite earlier push.
callback(null, prices);
});
},
Is this a scoping issue? I'm not really sure why prices is not pushed to.
Thanks very much.

If you know jquery, you could try deferred object
getLatestMarketPrices: function(username, callback) {
var prices = [];
var defer = $.Deferred();
//Attach a handler to be called when the deferred object is resolved
defer.done(function(){
console.log(prices);
callback(null, prices);
});
db.find('portfolio', {user: username}, function(err, stocks) {
for(var i = 0; i < stocks.length; i++) {
module.exports.getQuote(stocks[i].stock, function(err, ustock) {
console.log(ustock.unitprice); // Retrieves 1.092
prices.push(ustock.unitprice); // Should push to prices array?
//resolve when we retrieve all
if (prices.length == stocks.length){
defer.resolve();
}
});
}
});
},
Update: or don't need deferred object at all:
getLatestMarketPrices: function(username, callback) {
var prices = [];
db.find('portfolio', {user: username}, function(err, stocks) {
for(var i = 0; i < stocks.length; i++) {
module.exports.getQuote(stocks[i].stock, function(err, ustock) {
console.log(ustock.unitprice); // Retrieves 1.092
prices.push(ustock.unitprice); // Should push to prices array?
//callback only when we receive all
if (prices.length == stocks.length){
console.log(prices);
callback(null, prices);
}
});
}
});
},

Related

Promises issue with async and sync - angular

Working on an mobile cordova/angular project. Below is a simple service call:
this.getSomeData = function (businessId) {
var deferred = $q.defer();
var query = "SELECT * FROM Stuff";
$cordovaSQLite.execute(db, query).then(function (res) {
deferred.resolve(res.rows);
}, function (err) {
deferred.reject(err);
});
return deferred.promise;
};
The issue is simple:
for (var k = 0; k < count; k++) {
myService.getSomeData($scope.model.stuff[k].id, k).then(function (data) {
// whatever
}
);
getSomeData is async, so by the time it returns, the k of the for cycle is far from correct.
I thought of passing k to the service method as a parameter:
for (var k = 0; k < count; k++) {
myService.getSomeData($scope.model.stuff[k].id, k).then(function (data) {
// whatever
}
);
And change the service method accordingly:
this.getSomeData = function (id, index) {
var deferred = $q.defer();
var query = "SELECT * FROM Stuff";
$cordovaSQLite.execute(db, query).then(function (res) {
deferred.resolve(res.rows, index);
}, function (err) {
deferred.reject(err);
});
return deferred.promise;
};
But that second parameter is ignored and is always undefined.
How to overcome this?
It sounds like you're running into a problem called "closure over the loop variable" and this issue is discussed in detail here:
JavaScript closure inside loops – simple practical example
In your case, however, the clean solution is to combine Array#map with $q.all():
$q.all($scope.model.visits.map(function (stuff) {
return myService.getSomeData(stuff.id);
})).then(function (results) {
// results is an array of the results of all the calls to getSomeData() in the correct order
});
Also, as Bergi points out, avoid the deferred antipattern:
this.getSomeData = function (id) {
var query = "SELECT * FROM Stuff";
return $cordovaSQLite.execute(db, query).then(function (res) {
return res.rows;
});
};
This is how I got it working. I tried using #JLRishe's suggestion but it wouldn't work. Turns out, I managed to pass more than one parameter through to the service method and back to the controller as well (by building an object than contains as many parameters I need).
myService.getSomeData().then(
function (stuff) {
// whatever
}
).then(function () {
for (var i = 0; i < $scope.model.stuff.length; i++) {
// HERE I SEND TWO PARAMETERS TO THE SERVICE METHOD
myService.getSomeMoreData($scope.model.stuff[i].id, i).then(
function (data) {
// whatever
}
);
}
});
this.getSomeMoreData = function (id, index) {
var deferred = $q.defer();
var query = "SELECT * FROM stuff";
$cordovaSQLite.execute(db, query).then(function (res) {
var moreStuff = [];
for (var i = 0; i < res.rows.length; i++) {
var junk = res.rows.item(i);
moreStuff.push(junk);
}
// HERE I RESOLVE AN OBJECT INSTEAD OF TWO PARAMETERS
deferred.resolve({
moreStuff: moreStuff,
index: index
});
}, function (err) {
deferred.reject(err);
});
return deferred.promise;
};

Asynchronous call of mongojs find function

I have one mongojs query such as:
db.mapping.find(
{ "provider":req.params.provider, "perId":mongojs.ObjectId(req.params.perId) },
function(err, que){
if(err)
res.send(err);
else if(que)
{
totalVideoList = [];
for (var i=0; i < que.length; i++)
{
myid = que[i].providerId;
db.ABC.find({}, function(err, que1){
if(err)
res.send(err);
var x = {};
for (var j=0; j < que1.length; j++)
{
searching(que1[j]);
}
videoList = [];
getVideo(requiredDocument);
totalVideoList = totalVideoList.concat(videoList);
});
}
res.json(totalVideoList);
}
else
res.json([]);
});
Currently I am always getting [] (empty array) as my response. The problem is due asynchronous nature of callback function of mongojs. Before the expected output comes in "totalVideoList" variable, it responds us with totalVideoList = [].
I don't know how to use async.each() here. Please help me to tackle this problem.
Assuming using async
db.mapping.find(
{ "provider":req.params.provider, "perId":mongojs.ObjectId(req.params.perId) },
function(err, que){
if(err)
res.send(err);
else if(que)
{
totalVideoList = [];
async.each(que, function(item, callback){
myid = item.providerId;
db.ABC.find({}, function(err, item){
if(err)
return callback(err);
var x = {};
for (var j=0; j < item.length; j++)
{
searching(item[j]);
}
videoList = [];
getVideo(requiredDocument);
totalVideoList = totalVideoList.concat(videoList);
callback(null);
});
}, function(asyncErr){
if(asyncErr)
return resp.json(asyncErr);
resp.json(totalVideoList);
});
}
else
res.json([]);
});

Concatenate several API request with NodeJS

I'm messing with SteamAPI in order to learn some NodeJS. Right now I'm trying to get games's info after an initial request to get the player's profile, once I have the games IDs stored in an array. The point is that I don't know how to "return" an array AFTER the whole ID array is iterated and all results has come from the server.
function getThumbs(game) {
return rq(
'http://store.steampowered.com/api/appdetails?appids=' + game,
{json: true},
function (error, response, bd) {
if(response.statusCode === 200 && bd[game].data) {
return bd[game].data.screenshots;
}
});
}
function getGamesThumbnails(games) {
var deferred = $q.defer(),
queue = [];
for (var y = 0; y < games.length; y++) {
var game = games[y];
var thumbs = getThumbs(game);
queue.push(thumbs);
}
$q.all(queue).then(
function (data) {
deferred.resolve(data);
},
function (err) {
deferred.reject(err)
}
);
return deferred.promise;
}
app.get('/blog',function(client_req,client_res){
rq('http://api.steampowered.com/IPlayerService/GetOwnedGames/v0001/?key=' + key + '&steamid=blablabla&format=json', function (error, response, body) {
var data = JSON.parse(body);
var games = data.response.games.map(function (game) {
return game.appid;
});
getGamesThumbnails(games).then(function (data) {
console.log(data)
})
});
});
Basically, you should use a callback, because like you are doing in getThumbsyou are returning the object, while you should return the value bd[game].data.screenshots;
function getThumbs(game, cb) {
return rq(
'http://store.steampowered.com/api/appdetails?appids=' + game,
{json: true},
function (error, response, bd) {
if(response.statusCode === 200 && bd[game].data) {
cb(null, bd[game].data.screenshots);
}
});
}
function getGamesThumbnails(games) {
var deferred = $q.defer(),
queue = [];
for (var y = 0; y < games.length; y++) {
var game = games[y];
getThumbs(game, function(err, value) {
queue.push(value);
});
}
$q.all(queue).then(
function (data) {
deferred.resolve(data);
},
function (err) {
deferred.reject(err)
}
);
return deferred.promise;
}
And plust to return the response to the client you have to use the client_res.send(VALUE)
so the bottom part would become like this:
app.get('/blog',function(client_req,client_res){
rq('http://api.steampowered.com/IPlayerService/GetOwnedGames/v0001/?key=' + key + '&steamid=blablabla&format=json', function (error, response, body) {
var data = JSON.parse(body);
var games = data.response.games.map(function (game) {
return game.appid;
});
getGamesThumbnails(games).then(function (data) {
client_res.send(data);
console.log(data)
})
});
});
Your getThumbs() function does not return a promise. $q.all only works on an array containing promises, whereas rq uses callbacks.
Try this:
function getThumbs(game) {
var deferred = $q.defer(),
rq(
'http://store.steampowered.com/api/appdetails?appids=' + game,
{json: true},
function (error, response, bd) {
if(response.statusCode === 200 && bd[game].data) {
deferred.resolve(bd[game].data.screenshots);
}
});
return deferred.promise;
}
Thank you both!
I tried Yuri's approach, but $q.all it doesn't seem to resolve the array of promises (nothing happens after the last request from getThumbs())
for (var y = 0; y < games.length; y++) {
var game = games[y];
var thumbs = getThumbs(game);
queue.push(thumbs);
}
$q.all(queue).then(
function (data) {
console.log(data)
deferred.resolve(data);
},
function (err) {
deferred.reject(err)
}
);

Code 141 success/error message not called on parse cloud code nested query

I keep receiving a code 141 error success/error was not called. I am running another function getCinemasInLocation which returns a JSON like: {result: [result1, result2]}. I want to iterate over this array and run a query each time the loop runs and all the results to an array. That is, the results of all oteration will be in an array. Am I doing it right?
//This function uses getCinemasInLocation to retrieve the movie objects that are showing in the cinemas
Parse.Cloud.define("getMovieIdsInCinemas", function(request, response) {
var cinemasInLocaton = [];
var theLocation = request.params.theLocation;
cinemasInLocation = Parse.Cloud.run("getCinemasInLocation", {theLocation: theLocation});
for (i = 0; i < cinemasInLocation.length; i++){
var query = new Parse.Query("showing");
var movieIds = [];
query.equalTo("cinema", {
__type: "Pointer",
className: "Cinema",
objectId: cinemasInLocation[i]
});
query.find({
success: function(results) {
for (var i = 0; i < results.length; i++) {
movieIds.push(results[i].get("movie"));
}
response.success(movieIds);
},
error: function() {
response.error("movie lookup failed 2");
}
});
}
});
This is the getCinemasInLocation that does not work
function getCinemasInLocation(theLocation) {
// some code
//var result = ["xiUXXYFhAl","Yanh9iDykk"];
//return result;
var result = new Parse.Promise();
var query = new Parse.Query("Cinema");
query.equalTo("Location", theLocation);
query.find({
success: function(objects) {
var cinemas = [];
for (var i = 0; i < objects.length; i++) {
var cinema = objects[i];
cinemas.push(cinema.id);
}
result.resolve(cinemas);
},
error: function(error) {
result.reject(error);
}
});
return result;
}
Parse.Cloud.run doesn't return an array. It returns a Promise. So, create a normal javascript function in the same file: getCinemasInLocation()
As #Delhi said, you can only call response.success() or response.error() once. So, don't put them in a loop.
Use Promises on parallel. So, let's use the loop of Underscore instead of the normal FOR loop. You can start multiple operations at once, and use Parse.Promise.when to create a new promise that will be resolved when all of its input promises is resolved. You can read more about this in the documentation: https://www.parse.com/docs/js_guide#promises-parallel
var _ = require('underscore');
function getCinemasInLocation(theLocation) {
// some code
var result = [id1, id2];
return result;
}
// This function returns the array of movieIds of a cinema
function getMovieIdsInCinema(cinemaId) {
var result = new Parse.Promise();
var query = new Parse.Query("showing");
query.equalTo("cinema", {
__type: "Pointer",
className: "Cinema",
objectId: cinemaId
});
query.find({
success: function(objects) {
var movieIds = [];
for (var i = 0; i < objects.length; i++) {
var movie = objects[i].get("movie");
movieIds.push(movie.id);
}
result.resolve(movieIds);
},
error: function(error) {
result.reject(error);
}
});
return result;
}
Parse.Cloud.define("getMovieIdsInCinemas", function(request, response) {
var cinemasInLocation = [];
var theLocation = request.params.theLocation;
cinemasInLocation = getCinemasInLocation(theLocation);
var promises = [];
_.each(cinemasInLocation, function(cinemaId) {
promises.push(getMovieIdsInCinema(cinemaId));
});
Parse.Promise.when(promises).then(
function() {
var result = [];
_.each(arguments, function(object) {
result.push(object); // each object is an array of movieIds
});
response.success(result); // return array of arrays
},
function(error) {
response.error(error);
}
);
});

Node.js - The function does not return data in select from table

I want to retrieve the unique id from the database and store them into the object (userslist).
Why can not I retrieve data into an object?
Object userslist is empty {}
I have this function in Node.js:
getOnlineUsers: function()
{
var userslist = {};
client.query(
'SELECT DISTINCT Aid FROM online',
function selectCb(err, results, fields) {
if (err) {
throw err;
}
if (results.length > 0) {
for (var i = 0; i < results.length; i++) {
var reader = results[i];
userslist[reader['Aid']] = {
fbid: reader['Aid']
}
}
}
}
);
return userslist;
}
Here's one example of what was discussed in the comments above.
Pass a callback to getOnlineUsers...
my_obj.getOnlineUsers(function(u_list) {
/* do something with the user list */
});
And have getOnlineUsers receive the callback argument, and invoke it...
// receive the callback----v
getOnlineUsers: function(cb_func) {
client.query(
'SELECT DISTINCT Aid FROM online',
function selectCb(err, results, fields) {
if (err) {
throw err;
}
var userslist = {}
if (results.length > 0) {
for (var i = 0; i < results.length; i++) {
var reader = results[i];
userslist[reader['Aid']] = {
fbid: reader['Aid']
}
}
}
cb_func(userslist); // <-- invoke the callback, passing the data
});
}
This is one approach, but basically illustrates that the continuation of the flow of code needs to take place in the callback passed to client.query.

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