SWIFT/CloudKit -更新记录并将其保存到容器中

I'm having a problem updating CloudKit records. What I want to achieve is the ability to allow users to vote for a book by clicking a tableview row. This tableview is currently filled using records from Cloud data. I'm stuck when I want to retrieve a record (ie. the selected tableview row), and increase its voteCount column by 1, then save it back to the cloud and reload the data in the tableview.I'm having a problem updating CloudKit records.