CKQueryOperation queryCompletionBlock返回零游标

Question

我正在使用CKQueryOperation获取CloudKit数据库。出于某种原因，每次我按下获取按钮时，第一次出现nil光标。它第二次获取并获取数据，一切都很好。当我检查recordFetchedBlock时，它确实会获取结果并将其追加，但是最后数组为空。我不明白为什么会这样。我想立即显示结果，因为它们已被获取。我认为问题出在nil光标上，但是我愿意接受其他建议。这是我的代码：

public class CloudKitDatabase {

static let shared = CloudKitDatabase()

var records = [CKRecord]()

let publicData = CKContainer.default().publicCloudDatabase

init() {
    self.fetchRecords()
}

func fetchRecords() {

    let predicate = NSPredicate(value: true)
    let query = CKQuery(recordType: "OECD", predicate: predicate)

    let queryOperation = CKQueryOperation(query: query)

    queryOperation.recordFetchedBlock = {
        record in
        self.records.append(record)


    }

    queryOperation.queryCompletionBlock = { cursor, error in
        DispatchQueue.main.async {
            if error != nil {
                print(error.debugDescription)
            } else {
                if cursor != nil {
                    self.queryServer(cursor!)
                } else {
                    print("CURSOR IS NIL")
                }
            }
        }

    }
    self.publicData.add(queryOperation)
}


func queryServer(_ cursor: CKQueryOperation.Cursor) {
    let queryOperation = CKQueryOperation(cursor: cursor)

    queryOperation.recordFetchedBlock = {
        record in
        self.records.append(record)

    }

    queryOperation.queryCompletionBlock = { cursor, error in
        DispatchQueue.main.async {
            if error != nil {
                print(error.debugDescription)
            } else {
                if cursor != nil {
                    self.queryServer(cursor!)
                } else {
                    print("CURSOR IS NIL")
                }
            }
        }
    }
    self.publicData.add(queryOperation)

}

调试区域告诉我：光标是零并且CloudKitDatabase.shared.records.isEmpty为true

Answer 1

首先在第一个查询上尝试一些配置；

   let queryOperation = CKQueryOperation(query: query)
   queryOperation.queuePriority = .veryHigh
   queryOperation.resultsLimit = 99 // built in limit is 400  

接下来，不要在调度中进行游标调用，而不要包含您的完成内容；

queryOperation.queryCompletionBlock =
{ cursor, error in

        if error != nil {
            print(error.debugDescription)
        } else {
            if cursor != nil {
                self.queryServer(cursor!)
            } else {
                print("CURSOR IS NIL")
                completion(nil)
            }
        }
}

和;

queryOperation.queryCompletionBlock = 
{ cursor, error in

        if error != nil {
            print(error.debugDescription)
        } else {
            if cursor != nil {
                self.queryServer(cursor!)
            } else {
                print("CURSOR IS NIL")
                completion(nil)
            }
        }

}

也不要忘记在fetchRecords的开头清空记录数组，否则连续调用将在数组中获得相同的记录。