Model caching

gistfile1.js

var Backbone = require('backbone');
var _        = require('lodash');

// extend `Backbone.AssociatedModel` with a create method, which will be
// used to create new models for us, instead of using `new`
// shamelessly inspired by Supermodel
var Cached = Backbone.AssociatedModel.extend({
  _cached: false,
  _ref: 0,
  ref: function () {
    if (!this._cached) {
      this.constructor.cache().add(this);
      this._cached = true;
    }
    this._ref++;
    return this;
  },

  unref: function () {
    if(--this._ref <= 0) {
      if (this._cached) {
        this.constructor.cache().remove(this);
        this._cached = false;
      }
    }
    return this;
  }
}, {
  create: function(attrs, options) {
    var cache = this.cache();
    var model;
    if (attrs && attrs.id) {
      model = cache.get(attrs.id);
      if (model) {
        return model.set(attrs);
      }
    } else if (_.isString(attrs) || _.isNumber(attrs)) {
      model = cache.get(attrs);
      if (model) {
        return model;
      }
    }

    // if a model has been created using `new` and not using `create`
    // and is passed in for a lookup the above check will not return
    // a model. in this case we don't want it to be recreated, but instead
    // just use the passed in instance
    var newModel = (attrs instanceof this) ? attrs : new this(attrs, options);

    // newly created models are automatically cached
    cache.add(newModel);
    newModel._cached = true;
    return newModel;
  },

  cache: function () {
    return this._cache || (this._cache = new Backbone.Collection());
  }
});

module.exports = Cached;