using mongoose population in Express - node.js

Question

There a lot of great examples in adding data in Schemas using population
But how to use this in Express including evaluation existing data and error handling? I already create an user but now I want to add a log to a existing user.
This is my Schema:
const logSchema = new Schema({
logTitle: String,
postedBy: {
type: mongoose.Schema.Types.ObjectId, ref: 'User'
}
});
const userSchema = new Schema({
_id: Schema.Types.ObjectId,
firstName: {
type: String,
required: true
}
});
mongoose.model('User', userSchema);
mongoose.model('Logs', logSchema);
Despite all the good examples I lost my way. It 's hard to use the nice examples in good working Express code.
const mongoose = require('mongoose')
const Log1 = mongoose.model('Logs');
const logCreate = function (req, res) {
const userid = req.params.userid;
Log1.create({
logTitle: req.body.logTitle,
postedBy: userid._id
});
module.exports = {logCreate
};
Do I first create a new log in 'Logs' and then evaluate the existing user? Can somebody give me a push in the right direction? Thanks in advance

Answer 1

You have to add an objectid to the postedBy field. Let's say you have the following routes:
router
.route('/logs/')
.get(ctrlLogs.logsGetAll)
.post(ctrlLogs.logsAddOne);
router
.route('/logs/:logid')
.get(ctrlLogs.logsGetOne);
Then we can define the controller functions as (this is ctrlLogs):
const mongoose = require('mongoose');
const Log = mongoose.model('Log');
module.exports.logsAddOne = (req, res) => {
Log.create({
logTitle: req.body.logTitle,
postedBy: req.body.postedBy
}, (err, newLog) => {
let response = {};
if (err) response = { status: 500, message: err };
else response = { status: 201, message: newLog };
return res.status(response.status).json(response.message);
});
};
module.exports.logsGetAll = (req, res) => {
Log
.find({})
.populate('postedBy')
.exec((err, logs) => {
let response = {};
if (err) response = { status: 500, message: err };
else if (!logs) response = { status: 404, message: [] };
else response = { status: 200, message: logs };
return res.status(response.status).json(response.message);
});
};
module.exports.logsGetOne = (req, res) => {
Log
.findById(req.params.logid)
.populate('postedBy')
.exec((err, log) => {
let response = {};
if (err) response = { status: 500, message: err };
else if (!log) response = { status: 404, message: `Log with id ${req.params.logid} not found.` };
else response = { status: 200, message: log };
return res.status(response.status).json(response.message);
});
};
I've removed a lot of whitespace and curly braces for brevity. You should also not create stuff with values directly from req.body or query directly with req.params.logid; the values have to be validated first. You can use a library such as express-validator for validation.
We can see that by posting a request to /logs with the following request body:
{
"logTitle": "test log 32",
"postedBy": "5a2d1ec83ef998431c726dfc"
}
we will create a log where the user with id 5a2d1ec83ef998431c726dfc is set as the postedBy user. If I get /logs/5a2d240c66d7b473a0aa6ec8 (the new log) I get:
{
"_id": "5a2d240c66d7b473a0aa6ec8",
"logTitle": "test log 32",
"postedBy": {
"_id": "5a2d1ec83ef998431c726dfc",
"firstName": "test",
"__v": 0
},
"__v": 0
}
We can see that the populated log returns the user as well.