lastModified changes when loading distant related objects

[Patrik-Lundqvist]

DS.lastModified will change when a distant object gets loaded which makes it hard to detect changes for a specific object.

DS.defineResource({
  name: 'user',
  endpoint: 'users',
  relations: {
      hasMany: {
          post: {
              localField: 'posts',
              foreignKey: 'userId'
          }
      }
  }
});

DS.defineResource({
    name: 'post',
    endpoint: 'posts',
    relations: {
        belongsTo: {
            user: {
                parent: true,
                localKey: 'userId',
                localField: 'user'
            }
        },
        hasMany: {
            comment: {
                localField: 'comments',
                foreignKey: 'postId'
            }
        }
    }
});

DS.defineResource({
    name: 'comment',
    endpoint: 'comments',
    relations: {
        belongsTo: {
            post: {
                parent: true,
                localKey: 'postId',
                localField: 'post'
            }
        }
    }
});

var user = DS.get('user', 1);
/*
  Load all the users posts with DS.loadRelations
  Load all comments of each post with DS.loadRelations
*/

// Look for changes in user 1
$scope.$watch(function () {
    return DS.lastModified('user', 1);
}, function () {
    console.log("User 1 has changed");
});

// Load a comment which belongs to a post which in turn belongs to user 1
DS.find('comment',1,{bypassCache:true}); // This will trigger the change in user 1

This makes it very hard to know when user 1 is updated. lastModified should probably only change when its own properties are changed (name and additions/deletions to its posts collection).

[jmdobry]

This is a good point. Wasn't really an issue until it became easy to link up the relations.

[jmdobry]

@Patrik-Lundqvist I think I might have fixed this. Can you try it again with the latest master?

[Patrik-Lundqvist]

It now updates properly for object properties like when changing name for a user. But now there is no way of detecting addition/deletion changes for a collection property in an object, like the user posts collection.

It would be nice if one could watch direct collection changes with something like this:

$scope.$watch(function () {
    return DS.lastModified('user', 1, ['posts']);
}, function () {
    console.log("User 1 posts has changed");
});

DS.inject('post', {id:1, content: 'test', userId: 1},{linkInverse: true}); 
// This should log "User 1 posts has changed"

Or maybe just update lastModified for the user on additions/deletions in the posts collection

[jmdobry]

Unfortunately, DS.lastModified just returns the timestamp of the last time the object changed. It has no control over why the timestamp would change.

You could do:

$scope.$watch(function () {
  return DS.lastModified('user', 1) + DS.lastModified('post');
}, function () {
  console.log("User 1 or posts has changed");
});

[Patrik-Lundqvist]

Yeah, I thought so. Well that might be another issue, this fix works as intended.

[jmdobry]

Okay