我们可以有两个领域吗？

Question

I just discovered Realm. I'm thinking of an architecture design where there's an iOS app, a Mac app, and a backend. The iOS app has a Realm (Realm Mobile Platform) that is connected to a Realm in the backend. The iOS app has another Realm (Realm Mobile Database). The backend has a database that stores files.

Here's what I'm thinking.

The iOS app gets some JSON from a third party API, parses it and compares it to the stuff in the Realm (the one connected to the backend). The stuff that's not in the Realm, gets sent to the Mac app, which will download the corresponding files from an external source, and then upload those files to the database. The Mac App then alerts the iOS app, which then puts those things into the Realm (the one connected to the backend). This is the 'update the backend' process.

Now, the iOS app compares both of its Realms together, and gets the stuff that isn't in the local Realm. It then downloads the files from the database using the links in those realm objects. Once they're downloaded, it adds those objects to its local Realm store. This is the 'sync the device with the backend' process.

Both Realms would be storing the same kind of object.

Extra:

Ideally, the device doesn't have to be in perfect sync with the database, and so will most likely have some subset of the backend Realm and the database files.

Is this combination of one Realm Platform and one Realm Database possible?

Answer 1

Yep! That should be possible. You can have any number of both synchronized and unsynchronized Realms in an app; you just need to make sure to coordinate the Configuration objects you use to instantiate them.

It's possible to easily copy Realm objects from one Realm to another:

let objectFromLocalRealm = //...
let synchronizedRealm = //...

try! synchronizedRealm.write {
   sychronizedRealm.create(*objectType*.self, value: objectFromLocalRealm, update: true)
}

If you use this method though, you need to make sure both the object itself, and any child objects in List s or otherwise have primary keys, or you can end up with multiple copies of the same object in the synchronized Realm.

Realm's test for equality is it checks that two Object instances are point to the same backing row in the database, so comparing two objects from different Realms might not work automatically. You may need to implement a manual comparison method that checks that certain property values match.