I am using sails.js to develop my first app. I have a waterline model as shown below.
//ModelA.js
module.exports = {
attributes: {
//more attributes
userId: {
model: 'user'
},
//more attributes
}
};
I am using the model in one of my controllers as shown below.
ModelA.find(options)
.populate('userId')
.exec(function (err, modelA) {
//some logic
//modelA.userId is undefined here
res.json(modelA); //userId is populated in the JSON output
});
How do I get access to the populated value inside the model?
ModelA.find returns array of items.
ModelA.find(options)
.populate('userId')
.exec(function (err, results) {
console.log(results[0].userId) //results is an array.
//res.json(modelA);
});
Or you can use ModelA.findOne for a single record
It's because find return an array of records. You have to use index to access an object and then userId of that object.
ModelA.find(options).populate('userId').exec(function (err, recordsOfModelA) {
if(err) console.log(err);
else console.log(recordsOfModelA[0].userId)
});
Related
I have created database with two collections. Each of these collections connected with relations.
Here I want to pass one item _id and check whether it passed to other collection as foreign key. If it's passed, I want to filter all items which consist as _id. How can I do that. Here my mongoose query and screenshot of db. Thank you
route.get("/:id",(req,res)=>{
Vehicles.find({
categories: [req.params.id]
}, (err, data)=>{
if(err){
console.log(err);
}else{
console.log(data);
}
});
PS: For an example I want to get all vehicles which have category id "60c58c2dcf82de0780051378" inside categories array.
Following the mongo document, you can query for all documents where categories is an array that contains the objectId req.params.id as one of its elements.
Vehicles.find({
categories: req.params.id,
}, (err, data) => {
if (err) {
console.log(err);
} else {
console.log(data);
}
});
I have a mongoose query like this:
var query = Events.findOneAndUpdate({ '_id': event._id,'participants._id':participant._id},{'$set': {'participants.$': participant}}, {upsert:false,new: true},function(err,result){
if(err){
return res.status(500).jsonp({
error: 'Unable to update participant'
});
}
console.log(result.participants[0]);
res.jsonp(result.participants[0]);
});
and the query works properly modifying the participants subdocument inside Events collection.
The problem:
I need only the modified participant to be returned as JSON and I am not in need of the entire participants array but I am not able to achieve this since I get all the participants when I do console.log(result.participants);
How do I get only the modified subdocument after the query?
You may have to use the native JS filter() method as in the following:
Events.findOneAndUpdate(
{ '_id': event._id, 'participants._id': participant._id },
{ '$set': { 'participants.$': participant } },
{ upsert: false, new: true },
function(err, result){
if(err){
return res.status(500).jsonp({
error: 'Unable to update participant'
});
}
var modified = result.participants.filter(function(p){
return p._id === participant._id
})[0];
console.log(modified);
res.jsonp(modified);
}
);
I have a function that is needed to get results.
When I give 1 as _id filter everything is OK.
collectionPersonnel
.find({ '_id' : 1 })
.toArray(function (err, personnel) {
console.log(personnel);
});
If I give filter another way for instance user[0]['personnel_id'] -that is store 1- then I get only [] result;
collectionPersonnel
.find({ '_id' : user[0]['personnel_id'] })
.toArray(function (err, personnel) {
console.log(personnel);
});
And then I've tried another way. But it doesn't work because I used a string(user[0]['personnel_id']) instead of an ObjectID.
var ObjectID = require('mongodb').ObjectID;
var personnelPK_Hex = (user[0]['personnel_id']).toHexString();
var personnelPK = ObjectID.createFromHexString(personnelPK_Hex);
What should I do?
Edit
All of my codes are below;
module.exports = {
show: function(req, res) {
User.native(function(err, collectionUser) {
if(err) {
console.log("There is no exist a User by current_id");
};
collectionUser
.find({'_id' : req.param('id')})
.toArray(function (err, user) {
Personnel.native(function(err, collectionPersonnel) {
if(err) {
// handle error getting mongo collection
console.log("There is no exist a Personel by current _id");
};
if(!collectionPersonnel) {
console.log("There is no exist a Personel by current _id");
};
// var ObjectID = require('mongodb').ObjectID;
// var personnelPK_Hex = (user[0]['personnel_id']).toHexString();
// var personnelPK = ObjectID.createFromHexString(personnelPK_Hex);
collectionPersonnel
.find({ '_id' : user[0].personnel_id })
.toArray(function (err, personnel) {
console.log(personnel);
});
});
});
});
}
};
And console's output is;
[]
Solved
Just like apsillers's said. I had given a numeric _id to collection, incorrectly.
I've fixed _id value and everything is OK.
Thank you all...
user[0]['personnel_id'] might be a string. For Mongo, "1" is different from 1, which is why your literal number 1 worked, but your variable (which holds a string) does not.
Instead, try using a unary plus to convert the string to a number: +user[0]['personnel_id'].
try to use like user[0].personal_id instead of user[0]['personnel_id'] please provide your schema design that would be better to figure out what exactly you are missing.
i tried like this
collectionPersonnel
.find({ '_id' : user[0].personnel_id })
.toArray(function (err, personnel) {
console.log(personnel);
});
I've got myself a question regarding associations in Sails.js version 0.10-rc5. I've been building an app in which multiple models are associated to one another, and I've arrived at a point where I need to get to nest associations somehow.
There's three parts:
First there's something like a blog post, that's being written by a user. In the blog post I want to show the associated user's information like their username. Now, everything works fine here. Until the next step: I'm trying to show comments which are associated with the post.
The comments are a separate Model, called Comment. Each of which also has an author (user) associated with it. I can easily show a list of the Comments, although when I want to display the User's information associated with the comment, I can't figure out how to populate the Comment with the user's information.
In my controller i'm trying to do something like this:
Post
.findOne(req.param('id'))
.populate('user')
.populate('comments') // I want to populate this comment with .populate('user') or something
.exec(function(err, post) {
// Handle errors & render view etc.
});
In my Post's 'show' action i'm trying to retrieve the information like this (simplified):
<ul>
<%- _.each(post.comments, function(comment) { %>
<li>
<%= comment.user.name %>
<%= comment.description %>
</li>
<% }); %>
</ul>
The comment.user.name will be undefined though. If I try to just access the 'user' property, like comment.user, it'll show it's ID. Which tells me it's not automatically populating the user's information to the comment when I associate the comment with another model.
Anyone any ideals to solve this properly :)?
Thanks in advance!
P.S.
For clarification, this is how i've basically set up the associations in different models:
// User.js
posts: {
collection: 'post'
},
hours: {
collection: 'hour'
},
comments: {
collection: 'comment'
}
// Post.js
user: {
model: 'user'
},
comments: {
collection: 'comment',
via: 'post'
}
// Comment.js
user: {
model: 'user'
},
post: {
model: 'post'
}
Or you can use the built-in Blue Bird Promise feature to make it. (Working on Sails#v0.10.5)
See the codes below:
var _ = require('lodash');
...
Post
.findOne(req.param('id'))
.populate('user')
.populate('comments')
.then(function(post) {
var commentUsers = User.find({
id: _.pluck(post.comments, 'user')
//_.pluck: Retrieves the value of a 'user' property from all elements in the post.comments collection.
})
.then(function(commentUsers) {
return commentUsers;
});
return [post, commentUsers];
})
.spread(function(post, commentUsers) {
commentUsers = _.indexBy(commentUsers, 'id');
//_.indexBy: Creates an object composed of keys generated from the results of running each element of the collection through the given callback. The corresponding value of each key is the last element responsible for generating the key
post.comments = _.map(post.comments, function(comment) {
comment.user = commentUsers[comment.user];
return comment;
});
res.json(post);
})
.catch(function(err) {
return res.serverError(err);
});
Some explanation:
I'm using the Lo-Dash to deal with the arrays. For more details, please refer to the Official Doc
Notice the return values inside the first "then" function, those objects "[post, commentUsers]" inside the array are also "promise" objects. Which means that they didn't contain the value data when they first been executed, until they got the value. So that "spread" function will wait the acture value come and continue doing the rest stuffs.
At the moment, there's no built in way to populate nested associations. Your best bet is to use async to do a mapping:
async.auto({
// First get the post
post: function(cb) {
Post
.findOne(req.param('id'))
.populate('user')
.populate('comments')
.exec(cb);
},
// Then all of the comment users, using an "in" query by
// setting "id" criteria to an array of user IDs
commentUsers: ['post', function(cb, results) {
User.find({id: _.pluck(results.post.comments, 'user')}).exec(cb);
}],
// Map the comment users to their comments
map: ['commentUsers', function(cb, results) {
// Index comment users by ID
var commentUsers = _.indexBy(results.commentUsers, 'id');
// Get a plain object version of post & comments
var post = results.post.toObject();
// Map users onto comments
post.comments = post.comments.map(function(comment) {
comment.user = commentUsers[comment.user];
return comment;
});
return cb(null, post);
}]
},
// After all the async magic is finished, return the mapped result
// (or an error if any occurred during the async block)
function finish(err, results) {
if (err) {return res.serverError(err);}
return res.json(results.map);
}
);
It's not as pretty as nested population (which is in the works, but probably not for v0.10), but on the bright side it's actually fairly efficient.
I created an NPM module for this called nested-pop. You can find it at the link below.
https://www.npmjs.com/package/nested-pop
Use it in the following way.
var nestedPop = require('nested-pop');
User.find()
.populate('dogs')
.then(function(users) {
return nestedPop(users, {
dogs: [
'breed'
]
}).then(function(users) {
return users
}).catch(function(err) {
throw err;
});
}).catch(function(err) {
throw err;
);
Worth saying there's a pull request to add nested population: https://github.com/balderdashy/waterline/pull/1052
Pull request isn't merged at the moment but you can use it installing one directly with
npm i Atlantis-Software/waterline#deepPopulate
With it you can do something like .populate('user.comments ...)'.
sails v0.11 doesn't support _.pluck and _.indexBy use sails.util.pluck and sails.util.indexBy instead.
async.auto({
// First get the post
post: function(cb) {
Post
.findOne(req.param('id'))
.populate('user')
.populate('comments')
.exec(cb);
},
// Then all of the comment users, using an "in" query by
// setting "id" criteria to an array of user IDs
commentUsers: ['post', function(cb, results) {
User.find({id:sails.util.pluck(results.post.comments, 'user')}).exec(cb);
}],
// Map the comment users to their comments
map: ['commentUsers', function(cb, results) {
// Index comment users by ID
var commentUsers = sails.util.indexBy(results.commentUsers, 'id');
// Get a plain object version of post & comments
var post = results.post.toObject();
// Map users onto comments
post.comments = post.comments.map(function(comment) {
comment.user = commentUsers[comment.user];
return comment;
});
return cb(null, post);
}]
},
// After all the async magic is finished, return the mapped result
// (or an error if any occurred during the async block)
function finish(err, results) {
if (err) {return res.serverError(err);}
return res.json(results.map);
}
);
You could use async library which is very clean and simple to understand. For each comment related to a post you can populate many fields as you want with dedicated tasks, execute them in parallel and retrieve the results when all tasks are done. Finally, you only have to return the final result.
Post
.findOne(req.param('id'))
.populate('user')
.populate('comments') // I want to populate this comment with .populate('user') or something
.exec(function (err, post) {
// populate each post in parallel
async.each(post.comments, function (comment, callback) {
// you can populate many elements or only one...
var populateTasks = {
user: function (cb) {
User.findOne({ id: comment.user })
.exec(function (err, result) {
cb(err, result);
});
}
}
async.parallel(populateTasks, function (err, resultSet) {
if (err) { return next(err); }
post.comments = resultSet.user;
// finish
callback();
});
}, function (err) {// final callback
if (err) { return next(err); }
return res.json(post);
});
});
As of sailsjs 1.0 the "deep populate" pull request is still open, but the following async function solution looks elegant enough IMO:
const post = await Post
.findOne({ id: req.param('id') })
.populate('user')
.populate('comments');
if (post && post.comments.length > 0) {
const ids = post.comments.map(comment => comment.id);
post.comments = await Comment
.find({ id: commentId })
.populate('user');
}
Granted this is an old question, but a much simpler solution would be to loop over the comments,replacing each comment's 'user' property (which is an id) with the user's full detail using async await.
async function getPost(postId){
let post = await Post.findOne(postId).populate('user').populate('comments');
for(let comment of post.comments){
comment.user = await User.findOne({id:comment.user});
}
return post;
}
Hope this helps!
In case anyone is looking to do the same but for multiple posts, here's one
way of doing it:
find all user IDs in posts
query all users in 1 go from DB
update posts with those users
Given that same user can write multiple comments, we're making sure we're reusing those objects. Also we're only making 1 additional query (whereas if we'd do it for each post separately, that would be multiple queries).
await Post.find()
.populate('comments')
.then(async (posts) => {
// Collect all comment user IDs
const userIDs = posts.reduce((acc, curr) => {
for (const comment of post.comments) {
acc.add(comment.user);
}
return acc;
}, new Set());
// Get users
const users = await User.find({ id: Array.from(userIDs) });
const usersMap = users.reduce((acc, curr) => {
acc[curr.id] = curr;
return acc;
}, {});
// Assign users to comments
for (const post of posts) {
for (const comment of post.comments) {
if (comment.user) {
const userID = comment.user;
comment.user = usersMap[userID];
}
}
}
return posts;
});
My first attempt at building something with Angular + express + mongodb, so I'm probably going about this completely the wrong way. Express is being used to serve up json. Angular then takes care of all the views etc.
I'm using Mongoose to interact with Mongo.
I have the following database schema:
var categorySchema = new mongoose.Schema({
title: String, // this is the Category title
retailers : [
{
title: String, // this is the retailer title
data: { // this is the retailers Data
strapLine: String,
img: String , // this is the retailer's image
intro: String,
website: String,
address: String,
tel: String,
email: String
}
}
]
});
var Category = mongoose.model('Category', categorySchema);
and in Express I have a couple of routes to get the data:
app.get('/data/categories', function(req, res) {
// Find all Categories.
Category.find(function(err, data) {
if (err) return console.error(err);
res.json(data)
});
});
// return a list of retailers belonging to the category
app.get('/data/retailer_list/:category', function(req, res) {
//pass in the category param (the unique ID), and use that to do our retailer lookup
Category.findOne({ _id: req.params.category }, function(err, data) {
if (err) return console.error(err);
res.json(data)
});
});
The above works - I'm just having big problems trying to get at a single retailer. I'm passing the category, and retailer id through... I've tried all sorts of things - from doing a find on the category, then a findOne on the contents within... but I just cant get it to work. I'm probably going about this all wrong...
I found this thread here: findOne Subdocument in Mongoose and implemented the solution - however, it returns all my retailers - and not just the one I want.
// Returns a single retailer
app.get('/data/retailer_detail/:category/:id', function(req, res) {
//pass in the category param (the unique ID), and use that to do our retailer lookup
Category.findOne({_id: req.params.category , 'retailers.$': 1}, function(err, data) {
console.log(data);
if (err) return console.error(err);
res.json(data)
});
});
Thanks,
Rob
Now that I see your full filter/query, you should be able to use the array positional operator in this case as part of the projection rather than doing client side filtering:
app.get('/data/retailer_detail/:category/:id', function(req, res) {
//pass in the category param (the unique ID), and use that to do our retailer lookup
Category.findOne({
/* query */
_id: req.params.category ,
'retailers._id' : req.params.id
},
{ /* projection */
"retailers.$" : 1
},
function(err, data) {
var retailer = _.where(data.retailers , { id : req.params.id });
if (err) return console.error(err);
res.json(retailer)
});
});
For the { "retailers.$" : 1 } to work properly, the query must include a field from an element in the array. The $ operator returns the first match only.
The guys next door use Mongo + Express and gave me some pointers: they explained to me how mongo worked, and advised I should use underscore.js to assist with my filter.
They said I needed to pull the entire category out - and then run the filter. I don't strictly need , 'retailers._id' : req.params.id} but they said to leave it in as it guaranteed that the category would only be returned if an item within it contained that information. I still don't really know why or how... So can't really mark this as solved.. it it solved, but I don't really get why as yet - so will do more reading :)
app.get('/data/retailer_detail/:category/:id', function(req, res) {
//pass in the category param (the unique ID), and use that to do our retailer lookup
Category.findOne({_id: req.params.category , 'retailers._id' : req.params.id}, function(err, data) {
var retailer = _.where(data.retailers , { id : req.params.id });
if (err) return console.error(err);
res.json(retailer)
});
});