nodejs parse mysql row to object

Question

I'm a little newbie in node.js + mysql + object oriented.

Following question here I would like the 'Content' object to use the values returned by a mysql query. What I'm doing now I find it is really redundant and possibly stupid as rows[0] itself is the object I want to use. Any better way for doing this? Or different approach if this is wrong also appreciated.

(I'm using binary uuid keys that must be hex-stringifyed again to send as resource response)

content.js:

function Content() {
  this.id = '';
  this.name = '';
  this.domain = '';
}

Content.prototype.validate = function(path, queryParams) {
  ...
  return true;
};

Content.prototype.whatever = function(apiVersion, params, callback) {
  ...
  return callback(null, newParams);
};

mysql.js:

MySQLDb.SELECT_CONTENT_ID = "SELECT id, name, domain FROM content WHERE id = UNHEX(?)";

MySQLDb.prototype.findContentByID = function(id, callback) {
  this.dbConnection.query(MySQLDb.SELECT_CONTENT_ID, [ id ],
      function(err, rows, fields) {
        var content = new Content();

        if (rows.length > 0) {
          var i = 0;
          for (var key in rows[0]) {
            if (rows[0].hasOwnProperty(key) && content.hasOwnProperty(key)) {
              // BINARY(16) --> HEX string
              if (fields[i].columnType === 254) {
                content[key] = rows[0][key].toString('hex').toUpperCase();
              } else {
                content[key] = rows[0][key];
              }
            } else {
              console.log('Column ' + key + ' out of sync on table "content"');
            }

            i += 1;
          }
        }

        callback(err, content);
      });
};

contentRes.js:

contentRes.GETWhatever = function(req, res) {
  db.findContentByID(req.params.id, function onContent(err, content) {
    if (err || !content.validate(req.path, req.query)) {
      return res.send({});
    }

    content.whatever(req.query.apiVersion, req.query.d,
        function onWhateverdone(err, params) {
          if (err) {
            return res.send({});
          }

          return res.send(params);
        });
  });
};

barry-johnson · Accepted Answer · 2014-03-01 18:50:07Z

0

I think a lot of people would say you are doing it generally the right way even though it admittedly feels redundant.

It might feel a little cleaner if you refactored your code such that you could call the Content() constructor with an optional object, in this case rows[0] although if you were keeping it clean you wouldn't have access to the fields so you would take a different approach to the data type conversion - either by selecting the HEX representation in query or simply having your Content() know it needs to convert the id property.

Keeping it fairly simple (by which I mean ignoring making the constructor a bit more intelligent as well as any error detection or handling), you would have:

function Content(baseObj) {
  this.id = (baseObj && baseObj.id) ? baseObj.id.toString('hex').toUpperCase() : '';
  this.name = (baseObj && baseObj.name) ? baseObj.name : '';
  this.domain = (baseObj && baseObj.domain) ? baseObj.domain : '';
}

Then you could do something like this:

MySQLDb.prototype.findContentByID = function(id, callback) {
  this.dbConnection.query(MySQLDb.SELECT_CONTENT_ID, [ id ],
  function(err, rows, fields) {
    if (err) return callback(err,null);
    return callback(err, new Content(rows[0]));
  });

You 'could' also grab the rows[0] object directly, HEX the UUID more or less in situ and modify the __proto__ of the object, or under Harmony/ES6 use the setPrototypeOf() method.

MySQLDb.prototype.findContentByID = function(id, callback) {
  this.dbConnection.query(MySQLDb.SELECT_CONTENT_ID, [ id ],
  function(err, rows, fields) {
    if (err) return callback(err,null);
    var content = rows[0];
    content.id = content.id.toString('hex').toUpperCase();
    content.__proto__ = Content.prototype;
    return callback(err, content);
  });

Note, I said you 'could' do this. Reasonable people can differ on whether you 'should' do this. __proto__ is deprecated (although it works just fine in Node from what I have seen). If you take this general approach, I would probably suggest using setPrototypeOf(), and install a polyfill until you are otherwise running with ES6.

Just trying to give you a couple of other more terse ways to do this, given that I think the redundancy/verbosity of the first version is what you didn't like. Hope it helps.

answered Mar 1, 2014 at 18:50

barry-johnson

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2 Comments

Miquel Over a year ago

Thanks Barry. I still feel it is redundant but this is how I ended doing it. In fact I inserted mysql connection in a singleton class and the rest of the classes call the mysql.query() (which is calling dbConnection.query())

barry-johnson Over a year ago

You're welcome. That approach (singleton) does get rid of at least some of the redundant boilerplate. I am very sympathetic to trying to simplify/streamline the DB handling code.

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