Realm migrations in Swift

Question

I have a Realm Object modeled as so

class WorkoutSet: Object {
     // Schema 0
     dynamic var exerciseName: String = \"\"
     dynamic var reps: Int = 0
              


        

Answer 1

You will need to invoke the migration. Merely creating a configuration, won't invoke it. There are two ways of doing this:

1. Set your configuration with migration as Realm's default configuration-

   let config = Realm.Configuration(
     // Set the new schema version. This must be greater than the previously used
     // version (if you've never set a schema version before, the version is 0).
     schemaVersion: 1,
   
     // Set the block which will be called automatically when opening a Realm with
     // a schema version lower than the one set above
     migrationBlock: { migration, oldSchemaVersion in
   
       if oldSchemaVersion < 1 {
         migration.enumerate(WorkoutSet.className()) { oldObject, newObject in
           newObject?["setCount"] = setCount
         }    
       }
     }
   ) 
   Realm.Configuration.defaultConfiguration = config   
   

OR

2. Migrate manually using migrateRealm :

migrateRealm(config)

Now your migration should work properly.

Answer 2

Because you just create Realm.Configuration. Migration block is invoked by Realm if needed. You cannot invoke migration directly.

So to be invoke migration block, you should set configuration object to Realm, or set as default configuration. Then create Realm instance.

So You need to do the following:

let config = Realm.Configuration(
    // Set the new schema version. This must be greater than the previously used
    // version (if you've never set a schema version before, the version is 0).
    schemaVersion: 1,

    // Set the block which will be called automatically when opening a Realm with
    // a schema version lower than the one set above
    migrationBlock: { migration, oldSchemaVersion in
        // We haven’t migrated anything yet, so oldSchemaVersion == 0
        switch oldSchemaVersion {
        case 1:
            break
        default:
            // Nothing to do!
            // Realm will automatically detect new properties and removed properties
            // And will update the schema on disk automatically
            self.zeroToOne(migration)
        }
})

let realm = try! Realm(configuration: config) // Invoke migration block if needed