Improve model associations with loader methods and promises

improve_model_assocs.js

/**
 * Adds a loader method to the model innstance that will automatically populate the property for the assoc after load
 * Example: this.belongsTo('User') will add a "loadUser" method
 * @param instance
 */
module.exports.improveAssocs = function(instance)
{
  var model = getModel();
  var type = instance.type;
  var def = model.descriptionRegistry[type];

  Object.keys(def.associations).forEach(function(assocType) {
    Object.keys(def.associations[assocType]).forEach(function(name) {
      var assoc = def.associations[assocType][name];
      var fnName = utilities.string.getInflection(assoc.name, 'constructor', (assocType === 'hasMany') ? 'plural' : 'singular');
      var loader = 'load' + fnName;
      var promise = 'load' + fnName + 'Promise';
      var getter = 'get' + fnName;
      var prop = utilities.string.getInflection(assoc.name, 'property', (assocType === 'hasMany') ? 'plural' : 'singular');

      // create assoc prop with empty value/array
      instance[prop] = (assocType === 'hasMany') ? [] : null;

      // now override getter to automatically set property
      instance[loader] = function(cb) {
        instance[getter](function(err, data) {
          instance[prop] = data;
          cb(err, data);
        });
      };

      // also add a promise method
      instance[promise] = promisifyModels.promisify(instance, loader);
    });
  });
};