CODEWITHSUNDEEP
iosobjective-crealm
Daniel Bowden
Daniel Bowden

Reputation: 988

Realm Collection notification not firing for updates not impacting query

I have run into an issue in Realm Objective-C v2.4.3 where the collection notification block is not firing for a modification if the modification does not affect the overall query results.

To give a simplified example.

A Feed object and FeedItem object. Feed has an items RLMArray property.

RLMArray<FeedItem *><FeedItem> *items

I have a collection notification block set up for RLMResults where the query is:

[Feed objectsWhere:@"ANY items.status > 0"]

Insertion changes will fire if I modify the status property from 0 -> 1. As would deletions if I had an upper bounds to the query and it moved out of that. However, any changes to a FeedItem's status property that continues to match the query (such as modifying it from 1 -> 2) will not trigger the notification change block as the overall query results are not impacted by this change.

I would've expected this change to fall under a modification as mentioned in the collection docs?

  • You’re notified about modifications whenever a property of an object has changed, which was previously part of the collection and is still part of it.

  • You modify the age property of a Dog belonging to that Person.

  • This makes it possible to discretely control the animations and visual updates made to the content inside your UI, instead of arbitrarily reloading everything each time a notification occurs.

Am I missing something to get this functionality working? The CollectionView's datasource is the RLMResults and I would like to reload an individual CollectionViewCell to reflect the update to the FeedItem's status.

Upvotes: 0

Views: 477

Answers (1)

Daniel Bowden
Daniel Bowden

Reputation: 988

In the meantime I have worked around this by adding a lastModified property to Feed and then when making a change on FeedItem I update last modified using the inverse relationship.

self.feed.lastModified = [NSDate date];

Not that great, but it fires a modification change in the collection notification which is what I was after.

Happy to accept another answer that has a better way to achieve this.

Also found two existing Realm github issues which I've commented on

https://github.com/realm/realm-cocoa/issues/4305#issuecomment-283688989

https://github.com/realm/realm-cocoa/issues/3885#issuecomment-283274197

Upvotes: 0

Related Questions