CKQueryOperation queryCompletionBlock 返回一个 nil 游标

Posted 2023-02-24

【中文标题】CKQueryOperation queryCompletionBlock 返回一个 nil 游标

【英文标题】：CKQueryOperation queryCompletionBlock return a nil cursor

【发布时间】：2020-04-19 14:51:38

【问题描述】：

我正在使用 CKQueryOperation 获取 CloudKit 数据库。出于某种原因，每次按下获取按钮时，我第一次得到一个零光标。第二次获取并获取数据时，一切都很好。当我检查 recordFetchedBlock 时，它确实会得到结果并附加它们，但最后数组是空的。我不明白为什么会这样。我想立即显示结果，因为它们已被提取。我认为问题出在 nil 光标上，但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： 光标为零 而 CloudKitDatabase.shared.records.isEmpty 为真

【参考方案1】：

首先在第一个查询中尝试一些配置；

   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并包含您的完成；

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 开始时清空您的记录数组，否则连续调用将在数组中获得相同的记录。