Partial upsert?

[tschbc]

Am curious if there's a way to way to only partially upsert a realm object.

Given the class:

public partial class MyObject : IRealmObject
{
    [PrimaryKey]
    public int Id { get; set; }

    public int Count { get; set; }

    public bool SomeLocalState { get; set; }
}

And the operation:

MyObject first = new() { Id = 1, Count = 0, SomeLocalState = true };
realm.Write(() => realm.Add(first));

MyObject second = new() { Id = 1, Count = 4, SomeLocalState = false };
realm.Write(() => realm.Add(second, update: true));

Does realm have a built-in way for me to say that SomeLocalState should not be overridden during upsert?

My use case is that we're downloading information from a server and I would like to save some amount of state to an object that has no meaning outside of our app.

[peppy]

I haven't tested, but have you attempted adding the realm [Ignored] attribute?

[tschbc]

I thought about that, but I do want to persist the value in realm.

One kind of workaround I was thinking of was storing some kind of <Name>LocalState companion object with the same primary key and using a backlink for it. I think that should work, but I haven't tested it yet.

[nirinchev]

You could also use automapper or a similar library and define a mapping rule that sets only a subset of all properties. Then, instead of doing an upsert, you'd need to lookup the existing object and map on top of it. In pseudocode, would look something like:

var second = new MyObject { ... };
realm.Write(() =>
{
    var existing = realm.Find<MyObject>(second.Id);
    if (existing == null)
    {
        realm.Add(second);
    }
    else
    {
        // this uses some predefined mapping rule that will
        // set Count, but not SomeLocalState
        mapper.Map(second, existing);
    }
});

[tschbc]

Interesting, first time I'm learning about automapping. In this case with my unfamiliarity I think it's a bit much to learn/involve a new library, but I'm happy to know of another way to solve this.

I ended up going with a local companion object.