When registering a new user using Mongoose & MongoDB i would like to fetch values from another collection before saving the user instance. Currently I use the following solution, but this causes the user to get saved twice... Even worse, if the user does not pass the first validation the save() inside the set method is called anyway... usually resulting in an uncaught exception.
My current code works the following way:
UserSchema.path('address.postCode').set(function(newVal, cb) {
var that = this;
this.model('PostCode').findOne({ postCode: newVal }, function(err, postCode) {
if(postCode) {
that.longitude = postCode.longitude;
that.latitude = postCode.latitude;
} else {
that.longitude = undefined;
that.latitude = undefined;
}
that.save();
});
return newVal;
});
Anyone know a better way to do this?
The SchemaType#set function expects a synchronous return. You have an asynchronous call inside this function and therefore the return will be called before PostCode returns its results.
Also, you shouldn't be calling save() inside the setter, since it will be saved anyway.
Since you want to fetch data from another model, you should use a pre middleware. For example:
UserSchema.pre('save', true, function (next, done) {
var that = this;
if(this.isNew || this.isModified('address.postCode')) {
this.model('PostCode').findOne({ postCode: that.address.postCode }, function(err, postCode) {
if(postCode) {
that.longitude = postCode.longitude;
that.latitude = postCode.latitude;
} else {
that.longitude = undefined;
that.latitude = undefined;
}
done();
});
}
next();
});
The second parameter passed to pre (true) is what defines this is an asynchronous middleware.
For more information in middlewares, check the mongoose docs.
Related
I have this function in the file A.js
exports.executeMethods = async function(_id) {
var customObject = new CustomObject(_id);
await customObject.someAction();
}
That gets called by B.js when a new document is inserted
exports.insertDocument = function(document) {
document.save(async function(err, document) { //let's say this document has _id = 1
if(err) {
//stuff
}
else {
A.executeMethods();
}
});
}
I need a way to execute another method in the same exact CustomObject object when the document with _id = 1 gets updated.
One thing I tried are Change Streams, I wrote another function in B.js
exports.watch_document = async function(_id) {
var changeStream = models.Task.watch(
[{
$match: {
_id: _id
}
}]
);
return await changeStream.next();
}
And I modified executeMethods from A.js
exports.executeMethods = async function(_id) {
var customObject = new CustomObject(_id);
await customObject.someAction();
var res = await B.watch_document(_id);
if(//condition) {
await customObject.someOtherAction();
}
}
But for some reason changeStream.next is not defined and also I don't think this solution is really efficent because I had to create a replica set to try this. Is there a better way? If not, why is it not defined? I have mongodb 4.0 with the latest version of mongoose
EDIT: I forgot to mention that this is a REST application and that the information needed before calling someOtherAction() has to be provided by an external user.
I have an api server and some script jobs. They are using the same function to pull a roster using mongoose and populate the players in the roster.
On the api server, this function is called normally. Using the script, it doesn't.
API example
function getRoster(id) {
var deferred = Q.defer();
Roster.find({_id:id}, 'playerRoster userId tournamentId').populate('playerRoster').exec(
function(err, roster) {
if (err) {
deferred.resolve(err);
}
deferred.resolve(roster[0]);
});
return deferred.promise;
}
api.post('/get_roster', function(req, res) {
// get tournament
var id = req.body._id;
var playerId = req.body.playerId;
getRoster(id).then(function(data) {
var roster=data;
res.json(roster);
});
});
Script
module.exports = function(config) {
this.getRoster=function(id) {
//return Roster.find({_id:id}, 'playerRoster userId tournamentId').exec( - THIS RETURNS
return Roster.find({_id:id}, 'playerRoster userId tournamentId').populate('playerRoster').exec(
function(err, roster) {
if (err) {
return err;
}
console.log('roster[0]',roster);
return roster[0];
});
}
this.tallyPoints = function(tournamentPlayer,sportsPlayers) {
var deferred = Q.defer();
var totalPoints =0;
console.log("tallyPoints 0 ",tournamentPlayer);
var rosterId = tournamentPlayer.player.roster[0];
console.log("tallyPoints 1 ",rosterId);
this.getRoster(rosterId).then(function(roster2){
console.log("tallyPoints 2 ",roster2);
...
deferred.resolve(totalPoints);
});
return deferred.promise;
}
return this;
};
In the script, neither logging for the roster[0] or tallyPoints 2 lines print, but there is no error either.
Why doesn't Roster.find return when I add populate? The only thing I can imagine is because playerRoster collection has 2000 records searching for ~10 and it hits some timeout that isn't being caught.
Any suggestion to clean it up is also appreciated.
Thanks
Moongoose supports promises for a long time. It's unsuitable to use callback-based Mongoose API where promises are desirable and the use of Q.defer with existing promises is known as Deferred antipattern (similarly, new Promise results in promise construction antipattern).
In its current state getRoster doesn't return a promise and doesn't handle errors correctly.
function getRoster(id) {
return Roster.find({_id:id}, 'playerRoster userId tournamentId').populate('playerRoster').exec()
.then(roster => roster[0]);
}
api.post('/get_roster', function(req, res) {
// get tournament
var id = req.body._id;
var playerId = req.body.playerId;
getRoster(id)
.then(function(data) {
var roster=data;
res.json(roster);
})
.catch(err => {
// handle error
});
});
Considering that only roster[0] is used, it likely should be changed to Roster.findOne.
It doesn't matter whether getRoster is used in Express route or elsewhere, it should work. It's unknown how module.exports = function(config) {...} module is used, but this may refer to wrong context if it isn't used as class. If getRoster and tallyPoints don't use config, they shouldn't reside inside this function.
I'm still a n00b with NodeJS so this question may be somewhat elementary.
I'm using MongoJS to read two logically related collections. The first find() returns a value that I pass to the second find() to get the information I need.
I've tried several strategies, the last one (snippet #1) being a class that I export.
Before that I just had a function that did a return, returning the desired value, i.e., "config[0]".
In this code all I did was set the "sapConfig" attribute to the word "test", but when I execute this code the value of "sapConfig" is always "null" after I call the "get_config()" method and - strangest of all - the reference to "this.sapConfig = 'test'" generates an error, i.e., "Cannot set property 'sapConfig' of undefined".
When I had the code just as a simple function with a return statement (snippet #2), no errors were generated but the value returned is always "undefined" although the console.log() statements show that the value of the variable being returned has the desired value. What gives?
Code Snippet #1: Returns Object
"use strict";
var mongojs = require('mongojs'); // MongoDB API wrapper
module.exports = function(regKey) {
this.regKey = regKey;
this.sapConfig = null;
this.get_config = function() {
// Read SAP connection information from our MONGO db
var db = mongojs('mongodb://localhost/MIM', ['Configurations','Registrations']);
db.Registrations.find({ key: this.regKey }, function(err1, registration){
console.log('Reg.find()');
console.log(registration[0]);
db.Configurations.find({ type: registration[0].type }, function(err2, config){
console.log('Config.find()');
console.log('config=' + config[0].user);
this.sapConfig = 'test';
});
});
}
this.get_result = function() {
return this.sapConfig;
}
}
Again, the code in snippet #1, when I make a call to "get_config()", results in an error when it executes the line "this.sapConfig = 'test'".
However, after this error I can execute "obj.get_result()" and I get the value to which it was initialized, i.e., null. In other words, that same code doesn't generate an error saying that the "this" is undefined as .in the "get_config()" method
Code Snippet #2: Using the "return" statement
"use strict";
var mongojs = require('mongojs'); // MongoDB API wrapper
module.exports = function(regKey) {
// Read SAP connection information from our MONGO db
var db = mongojs('mongodb://localhost/MIM', ['Configurations','Registrations']);
db.Registrations.find({ key: regKey }, function(err1, registration){
console.log('Reg.find()');
console.log(registration[0]);
db.Configurations.find({ type: registration[0].type }, function(err2, config){
console.log('Config.find()');
console.log('config=' + config[0].user);
return config[0].user;
});
});
}
When I receive the return value and inspect it, it's "undefined". For example, at the Node CL I issue the following commands:
var config = require('./config') // The name of the module above
> var k = config('2eac44bc-232d-4667-bd24-18e71879f18c')
undefined <-- this is from MongoJS; it's fine
> Reg.find() <-- debug statement in my function
{ _id: 589e2bf64b0e89f233da8fbb,
key: '2eac44bc-232d-4667-bd24-18e71879f18c',
type: 'TEST' }
Config.find()
config=MST0025
> k <-- this should have the value of "config[0]"
undefined
You can see that the queries were successful but the value of "k" is "undefined". What's going on here?
I don't care which approach I use I just need one of them to work.
Thanks in advance!
this.sapConfig is not accessible. Thats because this refers to within the current function. What I like todo, is have a variable that refers to the function instance that you know sapConfig is located in.
Ex:
function Foo() {
var self = this;
this.test = "I am test";
var bar = function(){
return function(){
console.log(this.test); //outputs undefined (because this refers to the current function scope)
console.log(self.test); //outputs "I am test";
}
}
}
Here is your first code snippit with my example implemented:
"use strict";
var mongojs = require('mongojs'); // MongoDB API wrapper
module.exports = function(regKey) {
var self = this;
this.regKey = regKey;
this.sapConfig = null;
this.get_config = function() {
// Read SAP connection information from our MONGO db
var db = mongojs('mongodb://localhost/MIM', ['Configurations', 'Registrations']);
db.Registrations.find({ key: this.regKey }, function(err1, registration) {
console.log('Reg.find()');
console.log(registration[0]);
db.Configurations.find({ type: registration[0].type }, function(err2, config) {
console.log('Config.find()');
console.log('config=' + config[0].user);
self.sapConfig = 'test';
});
});
}
this.get_result = function() {
return self.sapConfig;
}
}
For your second snippet. You are trying to return a value from within your nested callback. Since nested functions are asyncronous, you cannot do that.
Here is how I like to return values from nested callbacks:
Ex2:
//Function example
var functionWithNested = function(done) {
//Notice the done param.
// It is going to be a function that takes the finished data once all our nested functions are done.
function() {
//Do things
function() {
//do more things
done("resultHere"); //finished. pass back the result.
}();//end of 2nd nested function
}(); //end of 1st nested function
};
//Calling the function
functionWithNested(function(result) {
//Callback
console.log(result); //resultHere
})
Here is your code using that example:
"use strict";
var mongojs = require('mongojs'); // MongoDB API wrapper
module.exports = function(regKey, done) {
// Read SAP connection information from our MONGO db
var db = mongojs('mongodb://localhost/MIM', ['Configurations', 'Registrations']);
db.Registrations.find({ key: regKey }, function(err1, registration) {
console.log('Reg.find()');
console.log(registration[0]);
db.Configurations.find({ type: registration[0].type }, function(err2, config) {
console.log('Config.find()');
console.log('config=' + config[0].user);
done(config[0].user);
});
});
}
//Then wherever you call the above function use this format
// if config is the name of the function export above...
new Config().(regKey, function(result){
console.log(result); //config[0].user value
})
Lots and lots of code, but I hope you were able to follow it. Let me know if you have any more questions! Cheers.
I need to edit a Game object by adding a User object to it. This is done by the mongoose query findById. This query works. But however, when I want to add the modified game to the resulting array, something goes wrong. The 'console.log(game);' returns the right output, but the 'console.log(result);' is always empty. What is going wrong? Is it something with inner functions?
var result = [];
games.forEach(function(game){
User.findById(game.user1_id, function(err, user){
if(err)
console.log(err);
game.user1 = user;
result.push(game);
console.log(game);
});
});
console.log(result);
You have run into a class callback problem. When you call forEach on games the code will actually continue outside the callback and the result will therefore be the value you first assigned to it, which is []. This is due to the code being evaluated asynchronous.
Solve this by moving your code into a function with a callback that is called when the loop is done, like this:
var utils = require('restberry-utils');
var getResult = function(next) {
var result = [];
utils.forEachAndDone(games, function(game, iter) {
User.findById(game.user1_id, function(err, user) {
if (err) console.log(err);
game.user1 = user;
result.push(game);
iter();
});
}, function() {
next(result);
});
};
getResult(function(result) {
console.log(result);
});
Notice I've imported the restberry-utils package and used the forEachAndDone method. This method will loop through the objects but won't continue unless you call the iter method. When it has looped through all the objects, the last callback is called which is where I'm returning the result.
Hope this makes sense.
I want to track the number of documents I have within a collection in a node.js server
using mongodb driver. I can insert, delete and update propperly but when I try to count, it works until I try to store that value, moment in which it returns nothing.
Here is my code:
var db_collection = db.collection('collection');
var countCollections = function () {
var response_count_collections = null;
db_mensajes.count(function(err,number_of_collections){
if (err){
console.log(err);
} else {
response_of_collections = number_of_collections;
console.log('Number of collections: '+number_of_collections);
}
});
return response_count_collections;
};
It logs the number_of_collections correctly but it doesn't return me the right value. In my example it returns null (how I defined my var response_count_collections;) and if I
try to return number_of_collections; within the db_collections.count()'s callback like this:
var db_collection = db.collection('collection');
var countCollections = function () {
var response_count_collections = null;
db_mensajes.count(function(err,number_of_collections){
if (err){
console.log(err);
} else {
console.log('Number of collections: '+number_of_collections);
return number_of_collections;
}
});
};
It returns me "undefined". Is there any way to achieve what I want?
Its because it returns the variable before the function is completely executed.
If you want it to be asynchronous then you will have to learn to control the flow of the program using some node modules like async.
Update:
Have a look at this question, it shows how to return value from an async function using callback correctly.