Realm Migration: Migrating objects to another

Question

I've added a new Model object to my realm objects and I am trying to move data from my old realm object properties to this new object.

In the old Schema, I have the following:

class Item: Object {
    @objc dynamic var image = ""
    @objc dynamic var coverImage = ""
    @objc dynamic var video = ""
}

In the new schema, I've added a new property called media so now it's looking this this

class Item: Object {
    @objc dynamic var image = ""
    @objc dynamic var coverImage = ""
    @objc dynamic var video = ""

    @objc dynamic var media: Media?
}

I've also added this new Model object:

class Media: Object {

    @objc dynamic var fullImage = ""
    @objc dynamic var thumbnailImage = ""
    @objc dynamic var video = ""

    var item = LinkingObjects(fromType: Item.self, property: "media")
}

My goal is to move the data from the old Item objects to the new Media objects.

I was trying to do something like this, but I don't know how to migrate that linking object, any help in the right direction would be appreciated.

 Realm.Configuration.defaultConfiguration = Realm.Configuration(
        schemaVersion: 1,
        migrationBlock: { migration, oldSchemaVersion in
            if (oldSchemaVersion < 1) {

                // enumerate first object
                migration.enumerateObjects(ofType: Item.className()) { oldItem, newItem in

                    let image = oldItem?["image"] as! String
                    let coverImage = oldItem?["coverImage"] as! String
                    let video = oldItem?["video"] as! String

                    //migrate second object
                    migration.enumerateObjects(ofType: Media.className(), { (oldMedia, newMedia) in

                    })
                }
            }
    })

Answer 1

You don't need to do anything with LinkingObjects, realm calculates those automatically when you query them.

All you'll need to do in your migration is set media to be a new Media object with the values you already have.

Other notes:

• The second enumerateObjects isn't needed.
• You can remove image, coverImage, and video from Item since you're moving those value to Media

---

Edit: This is what you would need to have in your migration.

let media = Media()
media.fullImage = oldItem?["image"] as! String
media.thumbnailImage = oldItem?["coverImage"] as! String
media.video = oldItem?["video"] as! String

newItem?["media"] = media