Question

让我们说你有一个像

这样的领域对象

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!
}

现在，我想升级数据库并将lastName提取到像这样的新类

中

$num = rand(0, count($family)-1);
$family[$num]

迁移会是什么样子？我尝试过一次简单的迁移，但这会导致多个LastName对象具有相同的primaryKey。

Answer 1

在AppDelegate 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

要添加，现在这也适用于primaryKey，模型看起来像这样：

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"
    }
}

但是如果由于lastName是每个对象的唯一标识符而导致primaryKey重复，则此迁移无法正常工作，因此您应该确保永远不会重复，在primaryKey对象中使用primaryKey的其他属性或根本不使用LastName。

具有非标准化数据的领域迁移

1 个答案: