change delegate

A Change Delegate is an object, inheriting from sudo.Model, that removes the need for the boilerplate code normally associated with handling the changeRecord objects returned from an observed Model.

###filter(changeRecord)

The lone method exposed by a Change Delegate, filter is intended to be bound as the callback when calling observe on a Model. The changeRecord passed to filter is inspected for a match (see filters below) and if found assembles and passes a 'data object' with the following properties to the specified method on the delegator:

{
  type: changeRecord.type,
  name: changeRecord.name,
  value: changeRecord.object[changeRecord.(name | path)],
  oldValue: changeRecord.oldValue
}

###filters

A hash of key:value pairs expected to be accessible by the delegate via this.get('filters'). The format of the object should be:

{
  foo: 'bar',
  'baz.qux': 'vot'
}

In the filter function, if a match is found between a key and changeRecord.name a method on the delegator with a name matching filters[changeRecord.name] will be called, bound to the scope of the delegator, passed the assembled 'data object'.

###In Use

A typical pattern would be to instantiate the Delegate from a delegator in its construction step (though it can be done anywhere):

var Foo = function(el, data) {
  this.construct(el, data);

  // establish your delegate
  this.addDelegate(new sudo.delegates.Change({
    filters: {
      bar: 'handleBar',
      'baz.qux': 'handleBazQux'
    }
  }));

  // observe a model instance but delegate
  // the job of inspecting the changeRecord
  someModel.observe(this.delegate('change', 'filter'));
};

Foo.prototype = $.extend(Object.create(sudo.View.prototype), {
  handleBar: function handleBar(data) {
    // do something with data.value
  },
  handleBazQux: function handleBazQux(data) {
    // do something with data.value
  }
});