David Weiss David Weiss - 3 days ago 4x
Swift Question

With Realm, should I use a List object or Results object as the data source for a UITableView?

There are at least 2 main collection types used in Realm:

  1. List

  2. Results

The relevant description from the documentation on a
object says:

Results is an auto-updating container type in Realm returned from
object queries.

Because I want my
to respond to any changes on the Realm Object Server, I really think I want my
to be backed by a
object. In fact, I think I would always want a
object to back my UI for this reason. This is only reinforced by the description of a
object in the documentation:

List is the container type in Realm used to define to-many

Sure seems like a
is focused on data modeling... So, being new to Realm and just reading the API, I'm thinking the answer is to use the
object, but the tutorial (Step 5) uses the
object while the RealmExamples sample code uses

What am I missing? Should I be using
objects to back my
? If so, what are the reasons?


Short answer: use a List if one already exists that closely matches what you want to display in your table view, otherwise use a Results.

If the data represented by a List that's already stored in your Realm corresponds to what you want to display in your table view, you should certainly use that to back it. Lists have an interesting property in that they are implicitly ordered, which can sometimes be helpful, like in the tutorial you linked to above, where a user can reorder tasks.

Results contain the results of a query in Realm. Running this query typically has a higher runtime overhead than accessing a List, by how much depends on the complexity of the query and the number of items in the Realm.

That being said, mutating a List has performance implications too since it's writing to the file in an atomic fashion. So if this is something that will be changing frequently, a Results is likely a better fit.