realmOC无法更新数据

Question

addobject是成功的。但我想更新数据。执行realm.beginWriteTransaction()后，断点无法继续执行backup.quanId = 5，就像跳过一样。

class YQQuanBackup: RLMObject {
    dynamic var groupId:Int = 0
    dynamic var quanId:Int = 0
    dynamic var content:String = ""
}

GCDBlock.async(.Default) {
    let results:RLMResults = YQQuanBackup.objectsWhere("groupId == %d", self.groupInfo!.groupId)
    let quanBackup = results.firstObject() as? YQQuanBackup
    guard let backup = quanBackup else { return }
    let realm = RLMRealm.defaultRealm()
    realm.beginWriteTransaction()
    backup.quanId = 5
    backup.content = YQRichTextUtil.richTextToPublishText(self.textView.attributedText, uploadedImageUrls: self.uploadedImageUrls)
    do {
        try realm.commitWriteTransaction()
    } catch {
        print(error)
    }
}