Service that returns data from an asynchronous method

Question

I am using Sails' ORM (Waterline). I have written a geturl service that should return the url of several models/actions in my app. I am currently calling this service inside my templates.

(As I am alone to develop this, don't hesitate to warn me if this design pattern is wrong)

Now it occurs that Waterline's .find() method is asynchronous (as it should). I always use callbacks to do things when inserting or fetching things in database.

Now I have seen everywhere that I cannot return any data from asynchronous methods. As a consequence I am puzzled because I want to create this [damned] service to centralize the URL management.

Here is my current code:

module.exports = {
    variete: function(id_objet) {
        var string = '/default_url';
        return onvariete(id_objet, function (err, url) {
          if (err) {
              sails.log.error('Error : ', err);
          } else {
              return url;
          }
        });
    }
};


function onvariete(id_objet, next) {
  var url = '/';
  return Variete.findOne({id:id_objet}).exec(function (err, v) {
    sails.log.info('URL Variety : '+ v.nom + ' / ' +id_objet + ' / ' + v.slug);
    if (err) {
      sails.log.error('Error : ' + v.nom + ' / ' + err);
      // Do nothing.
      return next(new Error('Variete error'), undefined);
    } else if (!v) {
      return next(new Error('Variete not found'), undefined);
    } else if (!v.slug) {
      // variete doesn't have a slug field
      // we redirect to /v/:id
      url += 'v/' + v.id;
      return next (null, url);
    } else {
      // Ok variete has got a slug field
      sails.log.info('GOT A SLUG! ' + v.slug);
      url += 'variete/' + v.slug;
      return next (null, url);
    }
  });
}

I made a static object that embeds my geturl service, and then inside a Jade template:

a(href="#{s.geturl.variete(ann.variete.id)}" title="#{ann.variete.name}") #{ann.variete.name}

And I can get something like:

<a title="Tomate Coeur de Boeuf" href="undefined">Tomate Coeur de Boeuf</a>

Thank you by advance.

Answer 1

The solution vas to write a .url(bool) instance method. See how to write instance methods in Sails / Waterline.

This way I directly access this method from my template : a(href="#{ann.variete.url()}" title="#{ann.variete.name}") #{ann.variete.name}.

Done!