When I run collection.find()
in MongoDB/Node/Express, I'd like to get a callback when it's finished. What's the correct syntax for this?
function (id,callback) {
var o_id = new BSON.ObjectID(id);
db.open(function(err,db){
db.collection('users',function(err,collection){
collection.find({'_id':o_id},function(err,results){ //What's the correct callback synatax here?
db.close();
callback(results);
}) //find
}) //collection
}); //open
}
That's the correct callback syntax, but what find
provides to the callback is a Cursor
, not an array of documents. So if you want your callback to provide results as an array of documents, call toArray
on the cursor to return them:
collection.find({'_id':o_id}, function(err, cursor){
cursor.toArray(callback);
db.close();
});
Note that your function's callback still needs to provide an err
parameter so that the caller knows whether the query worked or not.
2.x Driver Update
find
now returns the cursor rather than providing it via a callback, so the typical usage can be simplified to:
collection.find({'_id': o_id}).toArray(function(err, results) {...});
Or in this case where a single document is expected, it's simpler to use findOne
:
collection.findOne({'_id': o_id}, function(err, result) {...});
Based on JohnnyHK answer I simply wrapped my calls inside db.open() method and it worked. Thanks @JohnnyHK.
app.get('/answers', function (req, res){
db.open(function(err,db){ // <------everything wrapped inside this function
db.collection('answer', function(err, collection) {
collection.find().toArray(function(err, items) {
console.log(items);
res.send(items);
});
});
});
});
Hope it is helpful as an example.
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