Node.js: Not able to return Mongoose find results

Question

I'm new to Node.JS and can't find a solution to this. I'm building a restful service to retrieve data from mongo.

app.js

var database = require('./database.js');
...

app.get('/metadata', function(req, res) {
    console.log("GET: metadata");
    res.send(database.getMetadata(null));
});

app.get('/metadata/:id', function(req, res) {
    console.log("GET: metadata");
    res.send(database.getMetadata(req.params.id));
});
...

database.js

exports.getMetadata = function (id) {
    console.log('getting metada...')
    if (id == null) {
        return FolderInfo.find({}, null, null, function (err, metadatas) {
            if (!err) {
                console.log(metadatas);
                return metadatas;
            } else {
                return console.log(err);
            }
        });
    }
    else {
        return FolderInfo.findById(id, function (err, metadatas) {
            if (!err) {
                return metadatas;
            } else {
                return console.log(err);
            }
        });
    }
}

I've tried many different approaches. But always get this as result:

{
    options: {
        populate: { }
    },
    _conditions: { },
    _updateArg: { },
    op: "find"
}

but my console.log(metadatas); line is printing the results to the console. I'm using all the latest packages. Can somebody help me?

Answer 1

You can't really mix synchronous returns with asynchronous functions like findById, as it goes against the basic nature of asynchronous operations: "exit now, complete later."

You'll have to adjust getMetadata to accept a callback function that can be called when findById has completed later:

exports.getMetadata = function (id, callback) {
   // ...
};

And, instead of returning metadatas only when there's not an err:

if (!err) {
    return metadatas;
} else {
   // ...
}

You'll want to call the callback in either case:

callback(err, err ? null : metadatas);

In context, that could be:

FolderInfo.find({}, null, null, function (err, metadatas) {
    if (err) {
        console.log(err);
    } else {
        console.log(metadatas);
    }

    callback(err, err ? null : metadatas);
});

Or possibly just:

FolderInfo.find({}, null, null, callback);

Then pass getMetadata a callback function that handles the response when called:

app.get('/metadata', function(req, res) {
    console.log("GET: metadata");
    database.getMetadata(null, function (err, data) {
        res.send(data);
    });
});