RLMException,对象类型需要迁移

Question

我有一个对象NotSureItem中,我有三个属性title的名字是从更名text和textDescription我已经后来添加和dateTime财产.现在,当我要运行我的应用程序时,它会在我想要向这些属性添加内容时崩溃.它显示以下声明.

'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()
}

Answer 1

只要您尚未发布应用程序,就可以删除应用程序并再次运行.

每次更改Realm对象的属性时,现有数据库都会与新数据库不兼容.

只要您还处于开发阶段,您只需从模拟器/设备中删除该应用程序并再次启动即可.

稍后当您的应用程序发布并更改对象的属性时,您必须实现向新数据库版本的迁移.

要实际执行迁移,您需要实现Realm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()

每当您的方案发生更改时,您必须增加schemaVersion迁移块并更新块中所需的迁移.

Answer 2

删除应用程序并重新安装不是一个好习惯.从我们第一次遇到迁移需求开始,我们应该在开发过程中加入一些迁移步骤.SilentDirge给出的链接很好:领域迁移文档,它为处理不同情况提供了很好的示例.

对于最小迁移任务,上述链接中的以下代码段可以自动执行迁移,并与AppDelegate的disFinishLaunchWithOptions方法一起使用:

let config = Realm.Configuration(
  // Set the new schema version. This must be greater than the previously used
  // version (if you've never set a schema version before, the version is 0).
  schemaVersion: 1,

  // Set the block which will be called automatically when opening a Realm with
  // a schema version lower than the one set above
  migrationBlock: { migration, oldSchemaVersion in
    // We haven’t migrated anything yet, so oldSchemaVersion == 0
    if (oldSchemaVersion < 1) {
      // Nothing to do!
      // Realm will automatically detect new properties and removed properties
      // And will update the schema on disk automatically
    }
  })

// Tell Realm to use this new configuration object for the default Realm
Realm.Configuration.defaultConfiguration = config

// Now that we've told Realm how to handle the schema change, opening the file
// will automatically perform the migration
let _ = try! Realm()

Answer 3

下面的代码对我有用

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions 
{  
RLMRealmConfiguration *config = [RLMRealmConfiguration    defaultConfiguration];
 config.schemaVersion = 2;
config.migrationBlock = ^(RLMMigration *migration, uint64_t  oldSchemaVersion) {
  // The enumerateObjects:block: method iterates
  // over every 'Person' object stored in the Realm file
  [migration enumerateObjects:Person.className
                    block:^(RLMObject *oldObject, RLMObject *newObject) {
    // Add the 'fullName' property only to Realms with a schema version of 0
    if (oldSchemaVersion < 1) {
      newObject[@"fullName"] = [NSString stringWithFormat:@"%@ %@",
                            oldObject[@"firstName"],
                            oldObject[@"lastName"]];
    }

    // Add the 'email' property to Realms with a schema version of 0 or 1
    if (oldSchemaVersion < 2) {
     newObject[@"email"] = @"";
    }
  }];
 };
[RLMRealmConfiguration setDefaultConfiguration:config];

// now that we have updated the schema version and provided a migration block,
// opening an outdated Realm will automatically perform the migration and
// opening the Realm will succeed
[RLMRealm defaultRealm];

return YES;
}

更多信息:https://realm.io/docs/objc/latest/#getting-started

Answer 4

只需增加架构版本

\n

Realm 将自动检测新属性和删除的属性

\n

var config = Realm.Configuration(\n            // Set the new schema version. This must be greater than the previously used\n            // version (if you've never set a schema version before, the version is 0).\n            schemaVersion: 2,\n            \n            // Set the block which will be called automatically when opening a Realm with\n            // a schema version lower than the one set above\n            migrationBlock: { migration, oldSchemaVersion in\n                // We haven\xe2\x80\x99t migrated anything yet, so oldSchemaVersion == 0\n                if (oldSchemaVersion < 1) {\n                    // Nothing to do!\n                    // Realm will automatically detect new properties and removed properties\n                    // And will update the schema on disk automatically\n                }\n        })\n        \n               \n        do{\n            realm = try Realm(configuration: config)\n            \n            print("Database Path : \\(config.fileURL!)")\n        }catch{\n            print(error.localizedDescription)\n        }\n

\n