Callback function with Nodejs + Mongoose, How to return only the search value?

Question

I already researched how to do this, but I still can not understand, where am I going wrong ? I researched how to do this type of function but I could not understand how to get an answer in my callback, always end up having 2 functions within the other.

Controller UserCtrl

    // Models
    var User = require('../models/user');

    var isUserSearch = function(email,callback){

        User.find({email:email},function(err,data){
            if(err) throw err;
            return callback(data);
        });

    }

    var isUser = function(email){

        var resp = isUserSearch(email,function(data){
            return data;
            console.log(data); // I get my data 
        });

        console.log("Response : " + resp); // undefined

        return resp;

    }

    var result = {
        gerarToken : gerarToken,
        isUser : isUser,
    }

    module.exports = result;

Model

// Model
var mongoose = require('mongoose');

// Schema
var Schema = mongoose.Schema({
    name : {
        type : String,
        require : true
    },
    email : {
        type : String,
        require : true,
        unique : true
    },
    password : {
        type : String,
        required : true
    },
    type : {
        type : Number,
        required : true,
        default : 1
    },
    created : {
        type : Date,
        default : Date.now
    }
});

var Data = mongoose.model('User', Schema);

module.exports = Data;

Context AuthCtrl

// Controllers

var Crypto = require('./cryptoCtrl');

var User = require('./UserCtrl');

// ----------- Login
var login = function(req,res){
    var data = req.body;
    var email = data.email;
    var password = Crypto.cryptoString(data.password);

    var existUser = User.isUser(email);

    if(existUser){

        // IsUser is a function to return the user array 
        // if it exists, otherwise it returns only a false 
        // boolean value. In the example I'm going to use this function

    }


}

antoniodvr · Accepted Answer · 2017-01-24 14:12:35Z

1

var resp = isUserSearch(email,function(data){
  return data;
  console.log(data); // I get my data 
});

console.log("Response : " + resp); // undefined

resp is undefined due to non-blocking asynchronous architecture node.js provide.

The line which you are trying to logging the value is executed when the function that return the data isUserSearch has not already finished.

Did you already try to call isUserSearch rather than isUser in you controller?

var login = function(req,res){
    var data = req.body;
    var email = data.email;
    var password = Crypto.cryptoString(data.password);

    User.isUser(email, function(existUser) {
       if(existUser){
          console.log('User exist', existUser);
        // IsUser is a function to return the user array 
        // if it exists, otherwise it returns only a false 
        // boolean value. In the example I'm going to use this function
       } else {
          console.log('User does not exist');
       }
    });
}

Then you can remove isUser and change:

var result = {
    gerarToken : gerarToken,
    isUser: isUserSearch,
}

edited Jan 24, 2017 at 14:12

answered Jan 24, 2017 at 13:57

antoniodvr

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1 Comment

Leonardo Marques Over a year ago

I'm beginning to understand, you know the right way for me to do this. What do I need to study specifically for this, can you give me an example? Thanks

chridam · Accepted Answer · 2017-01-24 14:09:48Z

You only need the isUserSearch function with the callback. Use the data returned in a callback in the AuthCtrl and you call this as:

Controller UserCtrl:

// Models
var User = require('../models/user');

var isUserSearch = function(email, callback){
    /* use findOne() which returns a single document that you can check if null */
    User.findOne({email: email}, function(err, user){ 
        if (err) throw err;
        return callback(!!user); // return a callback with a Boolean value as argument
    });
}

var result = {
    gerarToken : gerarToken,
    isUser: isUserSearch,
}

module.exports = result;

Context AuthCtrl:

// Controllers

var Crypto = require('./cryptoCtrl');

var User = require('./UserCtrl');

// ----------- Login
var login = function(req, res){
    var data = req.body;
    var email = data.email;
    var password = Crypto.cryptoString(data.password);

    /* Call the isUser function with a callback */
    User.isUser(email, function(userExists){
        if (userExists) {
            // userExists is a boolean value
        }
    });

}

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