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iosmultithreadingrealm

Is it acceptable to load Realm objects in the main ui thread?

we are adopting (Swift)Realm as a data store in our iOS app and we are really pleased with it so far. We have a question around the design for the retrieval and storage of objects with Realm and multi-threading:

Is it acceptable to load objects in the main ui thread?

  • We know about the constraints that objects loaded with realm cannot be shared between threads.
  • We are also not seeing any performance issues yet, but our approach so far is to load all kinds of resources in background threads.
  • In the case where we load and filter some data and register a notification block, we don't see problems with using the main ui thread, but how would we handle a situation, where we for example want to display all data in a table view?
Solution

  • Is it acceptable to load objects in the main ui thread?

    Yes, it is in most cases* acceptable and fast enough. It wouldn't be acceptable if reading from the database would block the user, but as there is no concept like faults, read access is always predictable fast. Only if you have a really complex object graph, where you need to do heavy pre-processing to be able to display the objects on the UI, it would make sense to employ a background thread and/or caching to warrant a good user experience.

    In the case where we load and filter some data and register a notification block, we don't see problems with using the main ui thread, but how would we handle a situation, where we for example want to display all data in a table view?

    A UITableView only request those cells which are currently visible on the screen and reuses the view containers. A Realm collection is similar in this lazy nature, when you don't filter it, it doesn't enlarge the memory pressure, because you get only object accessors for those objects which you pull out of it. There is no need for pagination as long as you rely on the builtin Realm Results or List collections. Only if you need to apply a custom and complex filter in a way which isn't supported by Realm, it might be necessary to process that on a background thread.