从承诺中选择MySQL node.js中的多个数据

Question

The concept of promises is very new for me (so far, I was working with async.each and async.waterfall) I want to use promises but i'm stuck right now.

I want to get "tags" from my db. I have two tables for this : One called 'tags' with every tag in it (with an ID) and another one 'user_tags' with every username saved and the ID of the tag that the user (username) created and saved into 'tags'.

I can put information in my DB but now I want to pull this out and log it out (I will display it later)

So far this is my idea :

var getUserprofile = function getUserprofile(username, callback){
  pool.getConnection(function (err, connection) {
    var dataUser = [];

    // Error check
    if (err) {
      console.log(err);
    }

    connection.query('SELECT * FROM users_tags FULL JOIN tags ON (tags.id = users_tags.t_id) WHERE users_tags.user_id=666;', username , function (err, rows, fields) {
      if (err) {
        connection.release();
        cb(err);
      } else if (rows.length < 1) {
        connection.release();
        cb("We don't have any informations about this user yet");

      } else {
        console.log("we pull the information right now");
        connection.release();
        callback(null, rows[0]);
      }
    });
  });
}

Is this a good idea ? What should I do if I want to use promises for this kind of function ? Thanks in advance for any help !!!

Answer 1

I would use Bluebird . You can "promisify" existing APIs with Promise.promisify or Promise.promisifyAll .

I would do something like

var Promise = require('bluebird'),
     ... //other deps;

var pool = Promise.promisifyAll(pool);
function getUserprofile(username){
    var connection = null;
    return pool.getConnectionAsync()
        .then(function (conn) {
             connection = Promise.promisifyAll(conn);
             return connection.queryAsync('...');
        })
        .then(function (results) {
             if (results.length < 1) {
                 return "We don't have any informations about this user yet";
             } else {
                 console.log("we pull the information right now");
                 return results[0];
             }
        })
        .catch(function (err) {
             console.log(err);
             throw err;
        })
        .finally(function () {
             if (connection) {
                 connection.release();
             }
        });
}