在领域迁移过程中创建领域对象

Question

您是否能够在迁移过程中创建领域对象？我想要提取现有领域对象的一部分并使用该数据创建一个新对象，但迁移总是会挂起。这是我的迁移代码

private class var migrationBlock: MigrationBlock { 
    return { migration, oldSchemaVersion in 
     if oldSchemaVersion < 1 { 
      print("Shema Version 0") 
      migration.enumerate(Transaction.className(), { (oldObject, newObject) -> Void in 
       let oldDate = oldObject!["date"] as! NSDate 
       let newTransactionDate = TransactionDate() 
       newTransactionDate.date = oldDate 
       try! Realm.getRealm().write { Realm.getRealm().add(newTransactionDate, update: true) } 
       newObject!["_date"] = newTransactionDate 
      }) 
     } 
    } 
} 

Answer 1

您可以使用Migration.create(_:value:)在迁移过程中创建对象。

https://realm.io/docs/swift/latest/api/Classes/Migration.html#/s:FC10RealmSwift9Migration6createFS0_FTSS5valuePSs9AnyObject__CS_13DynamicObject

它返回MigrationObject的实例。所以你应该使用下标来为它的属性赋值。

let oldDate = oldObject!["date"] as! NSDate 

let newTransactionDate = migration.create(TransactionDate.className()) 
newTransactionDate["date"] = oldDate 

newObject!["_date"] = newTransactionDate