Problem

if oldSchemaVersion < 8 {
    migration.enumerateObjects(ofType: "UserContact") { oldObject, newObject in
        newObject!["displayName"] = oldObject!["firstName"] + " " + oldObject!["lastName"]
    }
}

if oldSchemaVersion < 9 {
    // 'UserContact' is removed, 'Contact' is introduced
    migration.enumerateObjects(ofType: "UserContact") { oldObject, newObject in
        let contact = migration.create("Contact", value: [
            "id": UUID().uuidString.lowercased(),
            "firstName": oldObject!["firstName"] as? String ?? "",
            "lastName": oldObject!["lastName"] as? String ?? "",
            "displayName": oldObject!["displayName"] as? String ?? "",
        ])
    }
    migration.deleteData(forType: "UserContact")
}

Coming from a schema version < 8, the migration to schema version 8 fails because there is no UserContact type anymore and newObject is nil.

At first glance the auto migration looks nice and handy but it is a total time consuming and error prone mess if you have to validate and fix all previous migration steps whenever a new schema version is introduced. Indeed it makes it nearly impossible to have a linear migration.

I also have an android app running where all migration steps and schema changes have to be done manually. Therefore there is no problem with linear migration. The current migration step is a bit more complex but it is "write once and forget". I cannot understand why there is no such thing in the swift sdk.

Currently i am at schema version 9. I don't even want to think about when i'm at schema version 100 and have to check all previous migration steps every time a new schema version is introduced.

Please add a feature to be able to disable automatic migration and to do exactly the same than in android . This would also remove the need to develop different migration logic for iOS and android.

Solution

No response

How important is this improvement for you?

Dealbreaker