CouchModel: ability to distinguish an external change (change tracker) from model being created with document, from model being reverted

[mz2]

It would be great to have separate overloadable public methods similar to -didLoadFromDocument for the three cases of:

1. model being created with document.
2. change tracker induced change to a model object.
3. a failed save of a model object.

Currently all three cases result in -didLoadFromDocument: being sent to the CouchModel object affected. This is because the method -didLoadFromDocument is called by both -initWithDocument: and by -couchDocumentChanged:, which in turn is called by -CouchDocument's -notifyChanged: and the error case in CouchModel's -saveCompleted:

[mz2]

Looks like overloading -couchDocumentChanged: in a CouchModel subclass makes it respond to only the cases 2 and 3 noted above. Something on these lines:

• (void)couchDocumentChanged:(CouchDocument *)doc
  {
  // couchDocumentChanged: not declared as a public method for CouchModel so need to performSelector: it
  if ([super respondsToSelector:@selector(couchDocumentChanged:)])
  [super performSelector:@selector(couchDocumentChanged:) withObject:doc];

  // do stuff in response to a change tracker induced change, or a failed model object save

}

Is there some way to get a response to only a change tracker induced change (isolate cases 2 and 3 from each other)?