I have a schema article defined as:
var ArticleSchema = new Schema({
title: String,
content: String,
creator: {
type: Schema.ObjectId,
ref: 'User'
}
})
And user schema:
var UserSchema = new Schema({
type: String, //editor, admin, normal
username: String,
password: String,
})
I need to query all the article created by editor, i.e. in sql language
select Article.title as title, Article.content as content
from Article inner join User
on Article.creator = User._id
where User.type = 'editor'
This is what I have tried
exports.listArticle = function(req, res, next) {
var creatorType = req.query.creatorType
var criteria = {}
if (creatorType)
criteria = {'creator.type': creatorType}
Article.find(criteria).populate('creator').exec(function(err, articles) {
if (err)
return next(err)
//ok to send the array of mongoose model, will be stringified, each toJSON is called
return res.json(articles)
})
}
The returned articles is an empty array []
I also tried Article.populate('creator').find(criteria), also not working with error:
utils.populate: invalid path. Expected string. Got typeof `undefined`
There is no concept of joins in MongoDB, as it is a not a relational database.
The populate method is actually a feature of Mongoose and internally uses multiple queries to replace the referred field.
This will have to be done using a multi-part query, first on the User collection, then on the Article collection.
exports.listArticle = function(req, res, next) {
var creatorType = req.query.creatorType
var criteria = {}
if (creatorType)
criteria = {'type': creatorType}
User.distinct('_id', criteria, function (err, userIds) {
if (err) return next(err);
Article.find({creator: {$in: userIds}}).populate('creator').exec(function(err, articles) {
if (err)
return next(err)
//ok to send the array of mongoose model, will be stringified, each toJSON is called
return res.json(articles)
})
})
}
Related
Using mongoose I am querying a list of posts and would like to determine whether or not the user has liked the image or not within the query function by adding a boolean to the response JSON. I am trying to do this in a for loop.
However, when I console.log(), the post with the field returns correctly but does not amend it to the JSON.
My function:
function(req, res) {
var isLiked, likeCount;
Post
.find(/* Params */)
.then(posts => {
for (var index in posts) {
posts[index].isLiked = posts[index].likes.includes(req.headers.userid)
console.log(posts[index]) // does not show 'isLiked' field in JSON
console.log(posts[index].isLiked) // response is correct
}
res.send(posts) // does not have 'isLiked field
})
},
Post schema:
var postSchema = new Schema({
userId: {
type: String,
required: true
},
caption: {
type: String,
required: false
},
likes: [{
type: String,
}]
});
To add properties to queries objects you should convert them to JS objects:
function getPosts(req, res) {
Post.find(/* Params */).then((posts) => {
const result = [];
for (const post of posts) {
const postObj = post.toObject();
postObj.isLiked = postObj.likes.includes(req.headers.userid);
result.push(postObj)
}
res.send(result);
});
}
Cuz
Post.find()
is not return an object, you can set prop isLiked to posts[index] but it's private.
Easy way to fix it is use lean() method to get return object
Post.find().lean()
.then(//do what you want)
What im doing:
When I call getData() the backend server .find() all my data.
My documents:
My test document has an _id a name and stuff fields. The stuff field contains the _id to the data document.
My data document has an _id and a age field
My goal:
When I send the data to the frontend I don´t want the stuff field to appear with the _id, I want it to appear with the age field from the correspondingdata.
What I have:
router.route('/data').get((req, res) => {
Test.find((err, aval) => {
if (err)
console.log(err);
else{
var result = [];
aval.forEach(e => {
var age;
// Get the age, only 1
Data.findById(e.stuff, 'age', function (err, a) {
age = a.age;
});
result.push({name: e.name, age: age});
});
res.json(result);
}
});
});
I find all the test documents then, for each one of them, I find the age and put the result in the array. Finaly I send the result array.
My problem:
The age field on my result array is always undefined, why? Any solutions?
UPDATE 1 - The schemas
The test schema
var TestSchema = new Schema(
{
stuff: {type: Schema.Types.ObjectId, ref: 'Data', required: true},
name: {type: String, required: true}
}
);
The data schema
var DataSchema = new Schema(
{
age: {type: Number, required: true}
}
);
router.route('/data').get((req, res) => {
Test.find({})
.populate('stuff')
.exec((err, aval) => {
if (err) console.log(err);
res.json(aval);
});
});
Mongoose model has a populate property that uses the value in the model attribute definition to get data matching the _id from another model.
It's a scop problem with your code try this out :
Data.findById(e.stuff, 'age', function (err, a) {
result.push({name: e.name, age: a.age});
});
But as a better solution think to use the Aggregation Framework
i'm creating simulation for goodreads by MERN stack
and when i'm using populate to retrieve books of specific user it returns empty array, i've done alot of search but in vain
here's my model
const userSchema =new mongoose.Schema({
firstName:{
type:"string",required:true
},
books:[{
book:{type:mongoose.Schema.Types.ObjectId,ref:'Book'},rate:Number,shelve:''
}]});
and this is books model
const bookSchema =new mongoose.Schema({
title :{
type:"string",required:true
}});
and this is how i use populate
router.get("/one", (req, res, next) => {
User.find({firstName : "John"}).populate("books").exec(function (err, user) {
res.json(user)
});
})
and this is the resulted json
[{"_id":"5c70f299ef088c13a3ff3a2c","books":[]}]
you are referencing the object book inside books array, so you need to populate books.book.
User.find({firstName : "John"}).populate("books.book").exec(function (err, user) {
res.json(user)
});
This REST endpoint updates the favourites list in my database, by removing qname from user.favourites.
My problem is that although updatedUser.favourites is correct at the end of the code, this is not actually being persisted in the database (similar code to add a qname on a separate endpoint do work). I'm sure this is a silly mistake, but what I've written feels intuitively correct.
exports.remQname = function (req, res, next) {
var userId = req.user.id;
var qname = req.params.qname;
console.log('addQname %s %s', userId, qname);
User.findOne({
_id: userId
}, function(err, user) {
if (err) return next(err);
if (!user) return res.json(401);
console.log(user);
// if the qname already in list, remove it, otherwise add it
var favourites = user.favourites;
var matches = _.remove(favourites, function (f) {
return f == qname
});
console.log('Matches: %s %s', matches, favourites);
user.favourites = favourites;
user.save(function(err, updatedUser){
if (err) throw err;
console.log(updatedUser); // correct info, but does not reflect database content
res.status(200).send(updatedUser.favourites);
});
});
};
Here is my Schema
var UserSchema = new Schema({
email: String,
password: String,
token: String,
role: {type: String, default: 'user'},
favourites: Array
});
module.exports = mongoose.model('User', UserSchema);
You can directly remove all instances of a specific value from an array field using $pull, so it would be more efficient to let MongoDB do the work rather than trying to manipulate the array yourself.
User.update({_id: userId},
{$pull: {favourites: qname}},
function(err, numberAffected, raw) { ... });
I'd also suggest changing your definition of favourites in the schema to be [String] instead of just Array if it does contain an array of strings.
It had something to do with lodash - this works instead
var newFavs = _.reject(user.favourites, function (f) {
return f == qname
});
console.log('Favourites - Old: %s New: %s', user.favourites, newFavs);
// delete user.favourites;
user.favourites = newFavs;
I read up that you can make Mongoose auto pouplate ObjectId fields. However I am having trouble structuring a query to populate fields in a subdoc.
My models:
var QuestionSchema = new Schema({
question_text: String,
type: String,
comment_field: Boolean,
core_question: Boolean,
identifier: String
});
var SurveyQuestionSchema = new Schema({
question_number: Number,
question: {type: Schema.Types.ObjectId, ref: 'Question', required: true} //want this popuplated
});
var SurveySchema = new Schema({
start_date: Date,
end_date: Date,
title: String,
survey_questions: [SurveyQuestionSchema]
});
Right now I achieve the effect by doing:
Survey.findById(req.params.id, function(err, data){
if(err || !data) { return handleError(err, res, data); }
var len = data.survey_questions.length;
var counter = 0;
var data = data.toJSON();
_.each(data.survey_questions, function(sq){
Question.findById(sq.question, function(err, q){
sq.question = q;
if(++counter == len) {
res.send(data);
}
});
});
});
Which obviously is a very error-prone way of doing it...
As I noted in the comments above, this is an issue currently under scrutiny by the mongoose team (not yet implemented).
Also, looking at your problem from an outsider's perpsective, my first thought would be to change the schema to eliminate SurveyQuestion, as it has a very relational db "join" model feel. Mongoose embedded collections have a static sort order, eliminating the need for keeping a positional field, and if you could handle question options on the Survey itself, it would reduce the schema complexity so you wouldn't need to do the double-populate.
That being said, you could probably reduce the queries down to 2, by querying for all the questions at once, something like:
Survey.findById(req.params.id, function(err, data){
if(err || !data) { return handleError(err, res, data); }
var data = data.toJSON();
var ids = _.pluck(data.survey_questions, 'question');
Question.find({_id: { $in: ids } }, function(err, questions) {
_.each(data.survey_questions, function(sq) {
sq.question = _.find(questions, function(q) {
var id = q._id.toString();
return id == sq.question;
});
});
res.send(data);
});
});