Develop Reference

FIrebase "pushing" object to an array is not working

app.get('/zones/:id/experiences', function(req,res) {
var zone_key = req.params.id;
var recent = [];
var ref = firebase.database().ref('participants/'+zone_key+'/experiences');
ref.on("value", function(snapshot) {
snapshot.forEach((snap) => {
firebase.database().ref('experiences').child(snap.val()).once("value").then((usersnap) => {
recent.push(usersnap.val());
});
});
console.log(recent);
});
res.render('experiences',{key: zone_key, list: recent});
});
In the above code, I am querying a reference point to get a set of "keys". Then for each key, I am querying another reference point to get the object associated to that key. Then for each object returned for those keys, I simply want to push the objects into a list. I then want to pass in this list to the client site to do stuff with the data using the render.
For some reason, the recent [] never gets populated. It remains empty. Is this an issue with my variables not being in scope? I console logged to check what the data the reference points are returning and its all good, I get the data that I want.
P.S is nesting queries like this ok? For loop within another query

As cartant commented: the data is loaded from Firebase asynchronously; by the time you call res.render, the list will still be empty.
An easy way to see this is the 1-2-3 test:
app.get('/zones/:id/experiences', function(req,res) {
var zone_key = req.params.id;
var recent = [];
var ref = firebase.database().ref('participants/'+zone_key+'/experiences');
console.log("1");
ref.on("value", function(snapshot) {
console.log("2");
});
console.log("3");
});
When you run this code, it prints:
1
3
2
You probably expected it to print 1,2,3, but since the on("value" loads data asynchronously, that is not the case.
The solution is to move the code that needs access to the data into the callback, where the data is available. In your code you need both the original value and the joined usersnap values, so it requires a bit of work.
app.get('/zones/:id/experiences', function(req,res) {
var zone_key = req.params.id;
var recent = [];
var ref = firebase.database().ref('participants/'+zone_key+'/experiences');
ref.on("value", function(snapshot) {
var promises = [];
snapshot.forEach((snap) => {
promises.push(firebase.database().ref('experiences').child(snap.val()).once("value"));
Promise.all(promises).then((snapshots) => {
snapshots.forEach((usersnap) => {
recent.push(usersnap.val());
});
res.render('experiences',{key: zone_key, list: recent});
});
});
});
});
In this snippet we use Promise.all to wait for all usersnaps to load.

Javascript function doesn't return query result

I am trying to figure out why one of my queries won't return the value from a query...my code looks like this:
var client = new pg.Client(conString);
client.connect();
var query = client.query("SELECT count(*) as count FROM sat_scores")
// Don't use demo key in production. Get a key from https://api.nasa.gov/index.html#apply-for-an-api-key
function getNEO(callback) {
var data = '';
query.on('rows', function(rows) {
console.log("Row count is: %s", rows[0].count)
data += rows[0].count;
});
query.on('end', function() {
callback(data);
});
}
with that, getNEO returns a blank...but if I set var data = '4', then getNEO returns 4....the query should return 128 but it just returns a blank...

First of all, getNEO() doesn't return anything - I'm operating on the assumption that you call getNEO() exactly once for your query, and pass in a callback to handle the data, and that callback is what's not getting the appropriate data?
My typical recommendation for troubleshooting things like this is to simplify your code, and try and get really close to any example code given (for instance):
var client = new pg.Client(conString);
// define your callback here, in theory
client.connect(function (err) {
if (err) throw err;
var query = client.query("SELECT count(*) as count FROM sat_scores"),
function(err, result) {
if (err) throw err;
console.log(result.rows.length);
}
);
});
... I'm doing a couple things here you'll want to note:
It looks like the client.connect() method is asynchronous - you can't just connect and then go run your query, you have to wait until the connection is completed, hence the callback. Looking through the code, it looks like it may emit a connect event when it's ready to send queries, so you don't have to use a callback on the connect() method directly.
I don't see a data event in the documentation for the query object nor do I see one in the code. You could use the row event, or you could use a callback directly on the query as in the example on the main page - that's what I've done here in the interest of simplicity.
I don't see the count property you're using, and row[0] is only going to be the first result - I think you want the length property on the whole rows array if you're looking for the number of rows returned.
I don't know if you have a good reason to use the getNEO() function as opposed to putting the code directly in procedurally, but I think you can get a closer approximation of what you're after like this:
var client = new pg.Client(conString);
// define your callback here, in theory
client.connect();
function getNEO(callback) {
client.on('connect', function () {
var query = client.query("SELECT count(*) as count FROM sat_scores"));
query.on('end', function(result) {
callback(result.rowCount);
});
});
}
... so, you can call your getNEO() function whenever you like, it'll appropriately wait for the connection to be completed, and then you can skip tracking each row as it comes; the end event receives the result object which will give you all the rows and the row count to do with what you wish.

so here is how I was able to resolve the issue....I moved the var query inside of the function
function getNEO(state, callback) {
var conString = "postgres://alexa:al#alexadb2.cgh3p2.us-east-1.redshift.amazonaws.com:5439/alexa";
var client = new pg.Client(conString);
client.connect();
var data = '';
var query = client.query("SELECT avg(Math) as math, avg(Reading) as reading FROM sat_scores WHERE State = '" + state + "'");
console.log("query is: %s", query);
query.on('row', function(row) {
console.log("Row cnt is: %s", row.math);
console.log("row is: " + row)
data += row;
});
console.log("made it");
query.on('end', function() {
callback(data);
});
}

asynchronous callback returns null

I am trying to assign callback function values and display ng-repeat
var myApp = angular.module('mybet',[]);
myApp.controller('MyBetController', function($scope,$firebase,ProfileFactory,MybetFactory){
$scope.myBetEvents = MybetFactory.getUsersBetsProfile(currentLoggedUser, function(betsData){
//Callback retuning null value here
$scope.myBetEvents = betsData;
});
});
myApp.factory('MybetFactory', ['$firebase', function($firebase){
var factory = {};
factory.getUsersBetsProfile = function(userId, callback){
var firebaseRef = new Firebase("https://xxx.firebaseio.com/usersbetsprofile").child(userId);
var firebaseBetsRef = new Firebase("https://xxx.firebaseio.com/events");
var userBettedEvent = [];
//retrive the data
firebaseRef.on('value', function (snapshot) {
console.log(snapshot.val());
var data = snapshot.val();
if (data){
//callback(data);
angular.forEach(data, function(data){
console.log('For Each getUsersBets',data);
var firebaseEventsData = firebaseBetsRef.child(data.event_id);
//retrive the data of bets
firebaseEventsData.on('value', function (snapshot) {
userBettedEvent.push(snapshot.val());
console.log('userBettedEvent',userBettedEvent);
//if I call callback here then i get the values but calling callback multipul time is no the option
}, function (errorObject) {
console.log('The read failed: ' + errorObject.code);
});
});
//ISSUE:: callback returing null values
callback(userBettedEvent);
}else{
console.log('Users has no bets');
}
}, function (errorObject) {
console.log('The read failed: ' + errorObject.code);
});
};
return factory;
}])
View::
<ul class="list">
<li class="item" ng-repeat="events in myBetEvents">{{events.event_name}}</li>
</ul>
How can get callback() to return values and display in view? what is causing callback after foreach returning null?

As #coder already said in the comments, your callback(userBettedEvent) is in the wrong place. Where you have it now, it will be invoked before the on('value' from Firebase has completed.
From the comments it is clear that you've notice that, yet only want the callback to invoked for one child. You can simply use a limit for that.
Something like this would work:
if (data){
data.limit(1).on('value', function(childData) {
var firebaseEventsData = firebaseBetsRef.child(childData.event_id);
firebaseEventsData.on('value', function (snapshot) {
userBettedEvent.push(snapshot.val());
callback(userBettedEvent);
}
})
I haven't really tested the code, but I'm quite sure a limit should get you in the right direction.
As a side note: you seem to be using Firebase as a traditional database, pulling the data out like you'd do with SQL. As you may notice: that is not a natural model for Firebase, which was made to synchronize data changes. If you want to stick to pulling the data, you may consider using once('value' instead of on('value' to ensure the handlers fire only once for every time you try to pull the data from Firebase.

Node.js & Node-Postgres: Putting Queries into Models

I would like to 'functionalize' my queries by putting them into functions which have apt names for the task.
I want to avoid putting everything in the req, res functions (my controllers), and instead put them in 'models' of sorts, that is, another JavaScript file that will be imported and used to run the functions that execute queries and return the results on behalf of the controller.
Assuming that I have the following setup for the queries:
UserController.js
exports.userAccount = function(req, res, next) {
var queryText = "\
SELECT *\
FROM users\
WHERE id = $1\
";
var queryValues = [168];
pg.connect(secrets.DATABASE_URL, function(err, client, done) {
client.query(queryText, queryValues, function(err, result) {
res.render('pathToSome/page', {
queryResult: result.rows
});
});
});
}
Here, while I'm in the query, I essentially redirect and render a page with the data. That works fine. But I want to take out all that pg.connect and client.query code and move it to a separate file to be imported as a model. I've come up with the following:
UserModel.js
exports.findUser = function(id) {
// The user to be returned from the query
// Local scope to 'findUser' function?
var user = {};
var queryText = "\
SELECT *\
FROM users\
WHERE id = $1\
";
var queryValues = [id];
pg.connect(secrets.DATABASE_URL, function(err, client, done) {
client.query(queryText, queryValues, function(err, result) {
// There is only ever 1 row returned, so get the first one in the array
// Apparently this is local scope to 'client.query'?
// I want this to overwrite the user variable declared at the top of the function
user = result.rows;
// Console output correct; I have my one user
console.log("User data: " + JSON.stringify(user));
});
});
// I expect this to be correct. User is empty, because it was not really
// assigned in the user = result.rows call above.
console.log("User outside of 'pg.connect': " + JSON.stringify(user));
// I would like to return the user here, but it's empty!
return user;
};
and I'm calling my model function as so:
var user = UserModel.findUser(req.user.id);
The query executes perfectly fine in this fashion - except that the user object is not being assigned correctly (I'm assuming a scope issue), and I can't figure it out.
The goal is to be able to call a function (like the one above) from the controller, have the model execute the query and return the result to the controller.
Am I missing something blatantly obvious here?

pgconnect is an asynchronous call. Instead of waiting for data to return from the database before proceeding with the next line, it goes ahead with the rest of the program before Postgres answers. So in the code above, findUser returns a variable that has not yet been populated.
In order to make it work correctly, you have to add a callback to the findUser function. (I told you wrong in a previous edit: The done parameter in pg.connect is called in order to release the connection back to the connection pool.) The final result should look something like this:
exports.findUser = function(id, callback) {
var user = {};
var queryText = "SELECT FROM users WHERE id = $1";
var queryValues = [id];
pg.connect(secrets.DATABASE_URL, function(err, client, done) {
client.query(queryText, queryValues, function(err, result) {
user = result.rows;
done(); // Releases the connection back to the connection pool
callback(err, user);
});
});
return user;
};
And you'd use it, not like this:
var user = myModule.findUser(id);
But like this:
myModule.findUser(id, function(err, user){
// do something with the user.
});
If you have several steps to perform, each of them dependent on data from a previous asynchronous call, you'll wind up with confusing, Inception-style nested callbacks. Several asynchronous libraries exist to help you with making such code more readable, but the most popular is npm's async module.

NodeJS | Passing an object as function parameter

I've had a small problem I couldn't overcome this week, I'm trying to pass a JSON object as a parameter in a function but it always tells me that I can't do that, but I don't want to end up sending the 50 values separately from my json object.
Here is the set up on my app, this is working as intended with express :
app.get('/', routes.index);
Here is the routing index from the previous line of code (Note that I'm using jade for rendering and I'm using the next function to pass parameters to it like the name in this one :
exports.index = function(req, res){
getprofile.profileFunc(function(result) {
res.render('index', { name: result });
});
};
Next it calls the function profileFunc from getprofile :
var profileFunc = function(callback) {
var sapi = require('sapi')('rest');
sapi.userprofile('name_here', function(error, profile) {
var result = [profile.data.name];
callback.apply(null, result);
});
};
exports.profileFunc = profileFunc;
Note that I was only able to pass a string result and have it displayed in the jade render, what I want to do is pass the profile object to use it in the render to display name, age, birthday but I can't get it to work, it will either pass a undefined object or not pass.
Thanks for taking time to read this.

I'll suggest the following:
var profileFunc = function(callback) {
var sapi = require('sapi')('rest');
sapi.userprofile('name_here', function(error, profile) {
callback.apply(null, profile);
});
};
exports.profileFunc = profileFunc;
...
getprofile.profileFunc(function(result) {
res.render('index', result);
});

If you put an Object into Jade's template context, then you'll have to reference it using the variable containing that Object. In your templates, you'd access that using name.foo, name.bar, etc.

Actually the problem is with apply, apply takes array as second argument so when you are trying to send object its not working. Just use callback function without apply like this:-
var profileFunc = function(callback) {
var sapi = require('sapi')('rest');
sapi.userprofile('name_here', function(error, profile) {
callback(profile);
});
};
exports.profileFunc = profileFunc;
...
getprofile.profileFunc(function(result) {
res.render('index', result);
});