Return insertId from an INSERT query

[yauri]

Hi, I have a problem with getting last insert id from a query.
Please take a look on the codes below

function Instructor(){}

Instructor.prototype = {

create: function(data) {

    connection.db.getConnection(function(err, conn){

      conn.query("INSERT INTO instructor SET ?", data, function(err,result){

        if(err) {

          throw err;

        }

        conn.end();
        console.log(result.insertId) //this is return a correct id

        return result.insertId; //this will return nothing

      });

    })

}
var data = {
    name: 'name',

    mail: 'ma...@gmail.com',
    phone: '12345'
}
var instructor = new Instructor();
var id = instructor.create(data);

Why id is undefined?

[// ravi]

You are getting tripped up by Node’s async’ness. Note that there are two (three actually) functions above: the one you call is create(), which kicks off an async call to the DB and returns back to your calling point, *without* any return value.

The second function, the callback to the DB query, where the results arrive, does return the insertId but to whom?

You will have to rethink your flow (pass a callback function where to instructor.create() and call that after conn.end() passing it the insertId), or use Promises or an Async library.

—ravi

[yauri]

Thanks ravi!!
I modified the function with callback and I can get the returned id! I'm new with javascript, in learning process :D

function Instructor(){}

Instructor.prototype = {

create: function(data, callback) {

    connection.db.getConnection(function(err, conn){

      conn.query("INSERT INTO instructor SET ?", data, function(err,result){

        if(err) {

          throw err;

        }

        conn.end(function(){

             callback(result.insertId); //this will return nothing   

        });  

      });

    })

}
var data = {
    name: 'name',

    mail: 'ma...@gmail.com',
    phone: '12345'
}
var instructor = new Instructor();

instructor.create(data,function(id){
     console.log(id); // I got the ID!

});

Thanks again :)

[// ravi]

On Jul 6, 2013, at 11:41 AM, yauri <yaurie...@gmail.com> wrote:
> Thanks ravi!!
> I modified the function with callback and I can get the returned id! I'm new with javascript, in learning process :D
>

You are welcome. Getting comfortable with Node’s async + JavaScript’s FP roots is a tricky business for sure. Before you fall prey to the callback pyramid of doom (http://twitpic.com/6rlqb5) consider an option like Promises (I suggest Q: https://github.com/kriskowal/q) or a flow library (I suggest Flow: https://github.com/willconant/flow-js). But I would also caution against letting these code-tamers prevent/protect you from understanding and getting comfortable with Node async and JavaScript closures.

2 cents,

—ravi

> function Instructor(){}
>
> Instructor.prototype = {
> create: function(data, callback) {
> connection.db.getConnection(function(err, conn){
> conn.query("INSERT INTO instructor SET ?", data, function(err,result){
> if(err) {
> throw err;
> }
> conn.end(function(){
> callback(result.insertId); //this will return nothing
> });
> });
> })
> }
> var data = {
> name: 'name',
> mail: 'ma...@gmail.com',
> phone: '12345'
> }
> var instructor = new Instructor();
> instructor.create(data,function(id){
> console.log(id); // I got the ID!
> });
>
> Thanks again :)
>

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[yauri]

Thanks for your information about this Pyramid of Doom!
So many things to learn about Javascript...