Trouble returning object through some Callbacks

Question

I am able to get data back but I seem to be failing at getting the result back up through some methods above this:

car.js

'use strict';

var Q = require('q');
var pg = require('co-pg')(require('pg'));
var config = require('../../models/database-config');

var car = module.exports = {};

car.find = Q.async(function *(id)
{
    var query = 'SELECT id, title, description FROM cars WHERE id = ' + id;

    var connectionResults = yield pg.connectPromise(config.connection);

    var client = connectionResults[0];
    var done = connectionResults[1];

    var result = yield client.queryPromise(query);
    done();

    console.log("value: " + result.rows[0].id);

    return result.rows;
});

this returns a valid value for my console.log so I know I'm getting data back.

But now when I try to pass that back up the stack, here I seem to be losing it after this method:

database.js

module.exports = {
    models: {
        car: _carModel
    },
    find: Q.async(_find)
};

    function _find(carId)
    {
        _carModel.find(carId)
        .then(function(result){
                 console.log('result[0].id: ' + result[0].id);

                return result;
         })
        .catch(function(error){
                console.log("promise error: " + error);
         })
        .done();
    };

So this also works, I get a valid value for console.log('result[0].id: ' + result[0].id);

But now when try to call this function, I lose the result:

gateway.js

var car = database.find(carId);
                 console.log("car: " + car.id);
...

here I get a'Cannot read property 'id' of undefined]'

UPDATE #2

So I am trying to propagate now the promise up, but still get undefined for the line console.log("returned car data: " + data); 'data' is undefined.

gateway.js

module.exports = {
    data: function(someData){
        _data = someData;
    },
    find: function(text, result){

        if(!text){
            results(null);
        };

        var endpoint =  _endpoint.replace(/_text/g, text);

         _client.query(endpoint, function(results){

             var cars = [];
             var car;

             for (var i = 0; i < results.docs.length; i++){

                 var carId = results.docs[i].id;

                 car = database.find(carId)
                 .then(function(data){
                         console.log("returned car data: " + data);
                     })
                 .done();

                 cars.push(car);
             }

             result(cars);
        });
    }

database.js

'use strict';
var Q = require('q');

var _obituaryModel = require('../../models/postgreSQL/obituary');

module.exports = {
    models: {
        obituary: _carModel
    },
    find: Q.async(_find)
};

function _find(carId)
{
    _carModel.find(carId)
    .then(function(result){

            console.log('result[0].id: ' + result[0].id);

            return result;
     })
    .catch(function(error){
            console.log("promise error: " + error);
     })
    .done();
};

carModel.js

'use strict';

var Q = require('q');
var pg = require('co-pg')(require('pg'));
var config = require('../../models/database-config');

var car = module.exports = {};

car.find = Q.async(function *(id)
{
    var query = 'SELECT id, title, description FROM cars WHERE id = ' + id;

    var connectionResults = yield pg.connectPromise(config.connection);

    var client = connectionResults[0];
    var done = connectionResults[1];

    var result = yield client.queryPromise(query);
    done();

    console.log("value: " + result.rows[0].id);

    return result.rows;
});

you can't return a value to the outer scope from an asynchronous callback. — Kevin B, Jul 30 '15 at 14:38
yea I see, and it also appears the result[0].id is called before I try to log car.id because of async also. So not sure how to handle this — PositiveGuy, Jul 30 '15 at 14:39

score 0 · Answer 1 · edited May 23 '17 at 12:14

0

You can't return data from an asynchronous function.

See here: How to return value from an asynchronous callback function?

edited May 23 '17 at 12:14

Community

1
1

answered Jul 30 '15 at 14:39

Wouter

756
3
11

score 0 · Answer 2 · answered Jul 30 '15 at 14:41

0

You are printing result[0].id on the console but reading result.id on the actual call:

Try

var car = database.find(carId);
             console.log("car: " + car[0].id);
...

answered Jul 30 '15 at 14:41

noderman

1,934
1
20
36

score 0 · Accepted Answer · answered Jul 30 '15 at 14:43

0

You have a promise object at your disposal, use it.

In database.js:

return _obituaryModel.find(carId)

and gateway.js

var car = database.find(carId);
car.then(function (data) {
    console.log(data);
});

answered Jul 30 '15 at 14:43

Kevin B

94,570
16
163
180

still not getting it working. I'll post my latest again. – PositiveGuy Jul 30 '15 at 15:01
I don't quite understand what you're doing with Q.async, i wonder if that's interfering with this suggestion. – Kevin B Jul 30 '15 at 15:03
that is the q middleware to allow your function to promise a result https://github.com/kriskowal/q – PositiveGuy Jul 30 '15 at 15:09
Since your function already returns a promise (after my update), i don't think you need it on _find – Kevin B Jul 30 '15 at 15:10
I finally got it. I'll post the answer shortly. Thanks a lot! – PositiveGuy Jul 30 '15 at 15:14
sorry I don't need what the car.find = part? – PositiveGuy Sep 10 '15 at 03:07
you said a while ago you said I didn't need something on _find, I wanted to know what you were referring to – PositiveGuy Sep 10 '15 at 04:23
i think i meant you don't need q.async on _find, but don't remember. – Kevin B Sep 10 '15 at 04:26
Thanks Kevin I think I recall now. – PositiveGuy Sep 10 '15 at 04:36

Trouble returning object through some Callbacks

3 Answers3