Swift RLMException，对象类型需要迁移

发布于10月27日

我有一个对象NotSureItem，其中有三个属性title，其名称从我后来添加的text和textDescription重命名，还有一个dateTime属性.现在，当我要运行我的应用程序时，当我想向这些属性添加内容时，它会崩溃.下面的语句显示了它.

'Migration is required for object type 'NotSureItem' due to the following errors:
- Property 'text' is missing from latest object model.
- Property 'title' has been added to latest object model.
- Property 'textDescription' has been added to latest object model.'

这是我的代码:

import Foundation
import Realm

class NotSureItem: RLMObject {
    dynamic var title = ""   // renamed from 'text'
    dynamic var textDescription = "" // added afterwards
    dynamic var dateTime = NSDate()
}

推荐答案

As long as you have not released your app你可以简单地删除你的应用程序并再次运行.

每次更改领域对象的属性时，现有数据库都会与新数据库不兼容.

只要你还在开发阶段，你就可以简单地从模拟器/设备中删除应用程序，然后重新启动.

如果要更改对象的属性，则必须实现到新数据库版本的migrations.

要实际执行迁移，需要实现一个领域迁移块.通常，您会将块添加到application(application:didFinishLaunchingWithOptions:):

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

            // if just the name of your model's property changed you can do this 
            migration.renameProperty(onType: NotSureItem.className(), from: "text", to: "title")

            // if you want to fill a new property with some values you have to enumerate
            // the existing objects and set the new value
            migration.enumerateObjects(ofType: NotSureItem.className()) { oldObject, newObject in
                let text = oldObject!["text"] as! String
                newObject!["textDescription"] = "The title is \(text)"
            }

            // if you added a new property or removed a property you don't
            // have to do anything because Realm automatically detects that
        }
    }
)
Realm.Configuration.defaultConfiguration = configuration

// opening the Realm file now makes sure that the migration is performed
let realm = try! Realm()

每当你的方案改变时，你必须增加迁移块中的schemaVersion，并更新块中所需的migrations.