Find which items from collection have changed with lastModified

[xvaldetaro]

Hi,

Is it possible to get which items have been modified from one lastModified call to another?

E.g.

var hash1 = DS.lastModified('document'); 
// Change some documents with update, save or inject
var hash2 = DS.lastModified('document');
DS.getModifiedItems(hash1, hash2);

Thanks a lot for the project, it is making my life much easier. I have been looking around for something like this since I saw the breeze.js video.

[jmdobry]

It's not possible right now. Angular-data doesn't keep a trail of hash changes, only the most recent.

I supposed I could implement a change history of configurable length. Each entry could include the timestamp of the change, the resourceName and id of the changed item, and the changes themselves. You could gather from that which items have changed. What do you thinK/

[xvaldetaro]

Looks like a very useful feature IMO. Besides from being able to pinpoint changes in a big collection, you give an undo feature for free.

The project I am working on is now leaving all the data for angular-data to manage, except for one resource that has a big collection and changes to individual documents must be observed by many parts of the application. This resource ATM needs a manager that dispatch events for updates in the collection, so I still keep this resource out of angular-data. I even thought about watching modifications for each individual document via lastModified but would be too much pain.

[jmdobry]

Here's a thought:

DS.defineResource('big-resource');

$scope.$watch(function () {
  DS.store['big-resource'].lastModified;
}, function (hashes, prevHashes) {
  var changedIds = [ ];
  angular.forEach(hashes, function (timestamp, id) {
    if (timestamp !== prevHashes[id]) {
      changedIds.push(id);
    }
  });

  // array of ids of items that changed
  console.log(changedIds);
}, true);

Edit: nevermind, this won't be sufficient

[xvaldetaro]

Correct me if I am wrong, but I am guessing that it is possible that a resource gets changed (and timestamped) multiple times between one $digest and another. Consequently, $watchers will be notified once via dirty checking and will think that only the last timestamp updates are the ones counting. So if the $watches cherry pick the updated documents they will miss previous updates.

If that is the case, isn't there a way to guarantee that all changes between two $digest are timestamped together?

[jmdobry]

If the browser doesn't support Object.observe then I don't think objects get timestamped multiple times between digest cycles. The digest cycles of angular-data and your app are tied together if your browser doesn't supportObject.observe`.

The change stream seems like a better option.