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
     // Schema 0 + 1
     dynamic var setCount: Int = 0
}

I am trying to perform a migration.

Within my AppDelegate I have imported RealmSwift.

Within the function didFinishLaunchWithOptions I call

Migrations().checkSchema()

Migrations is a class declared in another file.

Within that file there is a struct declared as so.

func checkSchema() {
    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)
            }
    })
}

func zeroToOne(migration: Migration) {
    migration.enumerate(WorkoutSet.className()) {
        oldObject, newObject in
        let setCount = 1
        newObject!["setCount"] = setCount
    }
}

I am getting an error for adding setCount to the model

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.