KO model with getters/setters and json update support

gistfile1.js

function FooModel () {
  Object.defineProperties(this, {
    _foo: {
      value: ko.observable(x.name),
      enumerable: true,
      configurable: true
    },
    _bar: {
      value: ko.observable(x.server_id || x.instance_id || x.instanceId),
      enumerable: true,
      configurable: true
    },
    _dontupdatethisone: {
      value: ko.observable(x.project_id),
      enumerable: true,
      configurable: true
    }
  });

  var self = this;

  // Generate public properties and Obs suffixed accessors; make source
  // property "private"
  var generateProperties = function (key) {
    // Create a property that accesses the underlying observable
    Object.defineProperty(self, key.substring(1) + "Obs", {
      enumerable: true,
      value: self[key]
    });

    // Create the "public" property
    Object.defineProperty(self, key.substring(1), {
      enumerable: true,
      get: function () { return self[key](); },
      set: function (n) { self[key](n); }
    });

    // Hide the "private" property
    Object.defineProperty(self, key, {
      enumerable: false, configurable: false
    });
  };

  // Generate additional properties for all _-prefixed properties
  _(self)
    .keys()
    .filter(function (key) { return _.startsWith(key, "_"); })
    .value()
    .forEach(generateProperties);


  /*** Handle Updating ***/

  // map the keys in json to the properties on your model
  var desiredKeys = {
    "foo": "foo",
    "bar": "bar"
  };

  Object.defineProperty(self, 'updateFromJson', {
    enumerable: true,
    value: function (data) {
      Object.keys(data)
        .forEach(function (key) {
          var modelKey = desiredKeys[key];
          if (!modelKey) return;

          if ( !_.isEqual(self[modelKey], data[key]) )
            self[modelKey] = data[key];  // I can use = syntax because I use Object.defineproperty with setters
        });
    }
  });
}

whoops, FooModel should take an argument, x, which is used in the constructor. and you can see various bits of OpenStack data structures referenced there, hehe