Swift中的Realm迁移

Question

我有一个Realm Object建模如此

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导入内RealmSwift.

在didFinishLaunchWithOptions我调用的函数内

Migrations().checkSchema()

迁移是在另一个文件中声明的类.

在该文件中有一个声明为这样的结构.

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
    }
}

添加setCount到模型时出错

Answer 1

您需要调用迁移.仅仅创建一个配置,不会调用它.有两种方法可以做到这一点:

1. 将迁移设置为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   
   

要么

2. 使用migrateRealm手动迁移:

migrateRealm(配置)

现在您的迁移应该正常运行.

Answer 2

因为你只是创建Realm.Configuration. 如果需要，Realm 会调用迁移块。您不能直接调用迁移。

所以要调用迁移块，你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