Backbone ajax mixin

ajax.js

App.Mixins.Ajax = {
  // Override urls in the target object to contain a map of
  // actionName => /url/path/with/:bound/:segments
  urls: {},

  // Any options specified here are merged with those you pass to
  // this.ajax({...}) before being passed to jQuery.ajax
  ajaxOptions: {},

  // Return the matching url from the 'urls' object, with /:path/:segments
  // bound to attribute values of the same name.
  // Return undefined if action is not a key of the 'urls' object.
  urlFor: function(action) {
    var url = this.urls[action];
    if (url) {
      url = url.replace(/:([^\/]+)/, _.bind(function(match, capture) {
        return (this instanceof Backbone.Model) ? this.get(capture) : this[capture];
      }, this));
    }
    return url;
  },

  // Simple wrapper for jQuery.ajax with some default options + events
  // - The "url" option is determined by calling urlFor on the 1st arg.
  //   if urlFor returns nothing, than an error is raised.
  // - Other options come from defaults, this.ajaxOptions, and the 2nd arg.
  // - On success, the "#{action}Success" event is triggered, and the
  //   "ajaxSuccess" event is triggered on Chorus.Comments.
  // - The "#{action}Error" and "ajaxError" events are triggered similarly.
  // - The "success" and "error" options are called from within the default
  //   callbacks, before any events are triggered.
  ajax: function(action, options) {
    var url = this.urlFor(action);
    if (!url) {
      throw 'ArgumentError: No url specified for action: ' + action;
    }

    // Create settings from defaults, this.ajaxOptions, and passed options
    var resource = this;
    var settings = _.extend({
      url: url,
      dataType: 'json',
      context: resource // Execute callbacks in the context of the resource
    }, this.ajaxOptions || {}, options);

    // Specify a default error callback that triggers some events
    settings.error = function(xhr, status, message) {
      // If a error callback was passed as an option, call it first
      if (options && _.isFunction(options.error)) {
        options.error.call(settings.context, resource, message);
      }
      // Trigger error events on both the resource, and on the global App object
      resource.trigger(action + 'Error', resource, message, xhr);
      App.trigger('ajaxError', xhr, status, message, resource);
    };

    // Specify a default success callback that triggers some events
    settings.success = function(response, status, xhr) {
      // If a success callback was passed as an option, call it first
      if (options && _.isFunction(options.success)) {
        options.success.call(settings.context, resource, response);
      }
      // Trigger success events on both the resource and on the global App object
      resource.trigger(action + 'Success', resource, response, xhr);
      App.trigger('ajaxSuccess', response, status, xhr, resource);
    };

    // Trigger start events for things like loading indicators to listen to
    resource.trigger(action + 'Start', resource);
    App.trigger('ajaxStart', resource);
    
    // Return the jqXHR object so more callbacks can be attached
    return jQuery.ajax(settings);
  }
};