Swift 中的领域迁移

Question

我有一个这样建模的领域对象

class WorkoutSet: Object {
     // Schema 0
     dynamic var exerciseName: String = ""
     dynamic var reps: Int = 0
     // Schema 0 + 1
     dynamic var setCount: Int = 0
}

我正在尝试执行迁移。

在我的 AppDelegate 中，我导入了 RealmSwift。

在函数 didFinishLaunchWithOptions 中调用

Migrations().checkSchema()

Migrations 是在另一个文件中声明的 class。

在该文件中有一个结构声明为如此。

func checkSchema() {
    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
            switch oldSchemaVersion {
            case 1:
                break
            default:
                // Nothing to do!
                // Realm will automatically detect new properties and removed properties
                // And will update the schema on disk automatically
                self.zeroToOne(migration)
            }
    })
}

func zeroToOne(migration: Migration) {
    migration.enumerate(WorkoutSet.className()) {
        oldObject, newObject in
        let setCount = 1
        newObject!["setCount"] = setCount
    }
}

我在将 setCount 添加到模型时遇到错误

Answer 1

您将需要调用迁移。仅仅创建一个配置，不会调用它。有两种方法：

将迁移配置设置为 Realm 的默认配置-

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

    if oldSchemaVersion < 1 {
      migration.enumerate(WorkoutSet.className()) { oldObject, newObject in
        newObject?["setCount"] = setCount
      }    
    }
  }
) 
Realm.Configuration.defaultConfiguration = config

或

使用 migrateRealm 手动迁移：

migrateRealm(config)

现在您的迁移应该可以正常进行了。

Answer 2

因为您刚刚创建 Realm.Configuration。如果需要，迁移块由 Realm 调用。您不能直接调用迁移。

所以要调用迁移块，您应该将配置对象设置为Realm，或者设置为默认配置。然后创建 Realm 实例。

因此您需要执行以下操作：

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
        switch oldSchemaVersion {
        case 1:
            break
        default:
            // Nothing to do!
            // Realm will automatically detect new properties and removed properties
            // And will update the schema on disk automatically
            self.zeroToOne(migration)
        }
})

let realm = try! Realm(configuration: config) // Invoke migration block if needed

Swift 中的领域迁移

Realm migrations in Swift

migration

data-migration

realm

data-management

swift