ios - Realm - 将对象添加到另一个对象内的列表

Question

我有这门课:

class IndiClass: Object {
    dynamic var MediIndiGrpId = 0
    dynamic var MediIndiGrpName = ""
    let Medis = List<MediClass>()

    override static func primaryKey() -> String? {
        return "MediIndiGrpId"
    }
}

我现在想在列表中添加一个 MediClass 对象。此代码显示了我如何获取对象以及如何尝试添加 MediClass 对象:

//Get a MediClass Object
let medi = realm.objectForPrimaryKey(MediClass.self, key: 1)
// Get the IndiClass Object
let indi = realm.objectForPrimaryKey(IndiClass.self, key: 1)
// Try to add the MediClass Object to the IndiClass Object:
indi!.Medis.append(medi!)

最后一行停止应用程序并在控制台中显示:

Terminating app due to uncaught exception 'RLMException', reason: 'Can't mutate a persisted array outside of a write transaction.'

Answer 1

如错误消息所述，持久化对象的变更必须发生在写入事务中:

// Get a MediClass Object
let medi = realm.objectForPrimaryKey(MediClass.self, key: 1)
// Get the IndiClass Object
let indi = realm.objectForPrimaryKey(IndiClass.self, key: 1)

try! realm.write {
    // Try to add the MediClass Object to the IndiClass Object:
    indi!.Medis.append(medi!)
}