ios - 具有非标准化数据的 Realm 迁移

Question

假设您有一个 Realm 对象，例如

class Person: Object {
    var dynamic firstName: String = ""
    var dynamic lastName: String = ""
}

现在，我想升级数据库并将姓氏提取到一个像这样的新类中

class LastName: Object {
    var dynamic sirName: String = ""

    override public class func primaryKey() -> String {
        return "sirName"
    }
}

class Person: Object {
    var dynamic firstName: String = ""
    var dynamic lastName: LastName!
}

迁移会是什么样子？我尝试过简单的迁移，但这可能会导致多个 LastName 对象具有相同的 PrimaryKey。

Answer 1

在您的AppDelegate的didFinishLaunchingWithOptions中:

let configuration = Realm.Configuration(
    schemaVersion: 1, //This must be larger than the previous schemaVersion
    migrationBlock: { migration, oldSchemaVersion in
        if oldSchemaVersion < 1 {
            migration.enumerate(Person.className()) { oldObject, newObject in
                let lastName = oldObject!["lastName"] as! String
                let newValue: [String: String] = ["sirName": lastName]
                let createdObject = migration.create(LastName.className(), value: newValue)
                newObject!["lastName"] = createdObject
            }
        }
})

Realm.Configuration.defaultConfiguration = configuration // Set the new configuration as default

let realm = try! Realm() // Open the default realm to perform the migration

要补充的是，现在这也适用于 primaryKey ，模型如下所示:

class Person: Object {
    dynamic var firstName: String = ""
    dynamic var lastName: LastName!
}

class LastName: Object {
    dynamic var sirName: String = ""

    override static func primaryKey() -> String? {
        return "sirName"
    }
}

但是，如果 lastName 存在重复项，则此迁移将不起作用，因为 primaryKey 是每个对象的唯一标识符，因此您应该确保有永远不会重复，请为 primaryKey 使用另一个属性，或者在 LastName 对象中根本不使用 primaryKey。