Is it possible to process a db.model.find() query inside of function context and retrieve a result without using callbacks and promises with mongoose library?
I need to get assured, if some user exists in process of running controller, so, I can't minimize current scope to callback due to large amount of same operations (for example, communication with database). Also I'm trying to realize MVC model in my project, so, I want to keep the helper libs (modules) in separated files. That's why I don't want to use any callbacks or promises - they will much times complicate everything even more then things already do.
user.js lib
var db = require('./lib/db');
class User{
constructor(id){ //get user by id
var result = db.models.user.findOne({_id: id}); //unsupported syntax in real :(
if(!result || result._id != _id)
return false;
else{
this.userInfo = result;
return result;
}
}
}
module.exports = User;
login model
var user = require('./lib/user')
var model = {};
model.checkUserLogged(function(req){
if(!req.user.id || req.user.id == undefined)
return false;
if(!(this.user = new user(req.user.id)))
return false;
else
return true;
});
module.exports = model;
login controller
var proxy = require('express').router();
proxy.all('/login', function(req, res){
var model = require('./models/login');
if(!model.checkUserLogged()){
console.log('User is not logged in!');
res.render('unlogged', model);
}else{
console.log('User exists in database!');
res.render('logged_in', model);
}
});
Generator functions/yields, async/await (es2017), and everything et cetera can be used just to solve the problem without nesting.
Thx in advance.
There are two points wrong:
If you don't want nested code an easy option could be to use async/await (currently available in Node.js using a flag, not recommended for production). Since Mongoose methods return promises they can be used with async/await.
But as I said you can not do that in the constructor, so it has to be somewhere else.
As an example you could do something like this:
var proxy = require('express').router();
var db = require('./lib/db');
proxy.all('/login', async function(req, res){
const result = await db.models.user.findOne({_id: req.user.id}).exec();
if (!result) {
console.log('User is not logged in!');
return res.render('unlogged');
}
res.render('logged_in');
});
Old question, but I want to share a method for handling this that I didn't see in my first couple searches.
I want to get data from a model, run some logic and return the results from that logic. I need a promise wrapper around my call to the model.
Below is a slightly abstracted function that takes a model to run a mongoose/mongo query on, and a couple params to help it do some logic. It then returns the value that is expected in the promise or rejects.
export function promiseFunction(aField: string, aValue, model: Model<ADocument, {}>): Promise<aType> {
return new Promise<string>((resolve, reject) => {
model.findOne({[aField]: aValue}, (err, theDocument) => {
if(err){
reject(err.toString());
} else {
if(theDocument.someCheck === true){
return(theDocument.matchingTypeField)
} else {
reject("there was an error of some type")
}
}
});
})
}