相关疑难解决方法(0)

我已经阅读了一些博客,但我仍然对如何使用NSPersistentContainer performBackgroundTask创建实体并保存它感到困惑.通过调用方便的方法创建一个实例后init(context moc: NSManagedObjectContext)的performBackgroundTask() { (moc) in }块,如果我检查container.viewContext.hasChanges这个返回false,并说没有什么保存的,如果我叫节省moc(该块所产生的背景MOC)我得到的错误是这样的:

fatal error: Failure to save context: Error Domain=NSCocoaErrorDomain Code=133020 "Could not merge changes." UserInfo={conflictList=(
    "NSMergeConflict (0x17466c500) for NSManagedObject (0x1702cd3c0) with objectID '0xd000000000100000 <x-coredata://3EE6E11B-1901-47B5-9931-3C95D6513974/Currency/p4>' with oldVersion = 1 and newVersion = 2 and old cached row = {id = 2; ... }fatal error: Failure to save context: Error Domain=NSCocoaErrorDomain Code=133020 "Could not merge changes." UserInfo={conflictList=(
    "NSMergeConflict (0x170664b80) for NSManagedObject (0x1742cb980) with objectID '0xd000000000100000 <x-coredata://3EE6E11B-1901-47B5-9931-3C95D6513974/Currency/p4>' …

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