来自私有区域的 CKQuery 仅返回 CloudKit 中的前 100 个 CKRecords答案

【问题标题】：CKQuery from private zone returns only first 100 CKRecords from in CloudKit来自私有区域的 CKQuery 仅返回 CloudKit 中的前 100 个 CKRecords
【发布时间】：2015-06-18 00:48:44
【问题描述】：

对 Cloudkit 私有默认区域的查询结果是否有任何限制？我不知道为什么我只收到带有以下查询的前 100 条记录：

let p = NSPredicate(format: "(type == 'entered') AND (timestamp >= %@) AND (timestamp <= %@)", from, to)
let q = CKQuery(recordType: self.beaconRecordType, predicate: p)
q.sortDescriptors = [NSSortDescriptor(key: "timestamp", ascending: true)]
self.privateDatabase?.performQuery(q, inZoneWithID: nil, completionHandler: { results, error in

    //count = 100
    println(results.count)

}

好的。正如 Edwin 在回答中提到的那样，解决方案是使用 CKQueryOperation 来获取初始数据块，然后使用 completionBlock 中的“光标”来触发另一个操作。这是一个例子：

更新

func fetchBeacons(from:NSDate, to:NSDate) {

    let p = NSPredicate(value: true)
    let q = CKQuery(recordType: self.beaconRecordType, predicate: p)

    let queryOperation = CKQueryOperation(query: q)

    queryOperation.recordFetchedBlock = fetchedARecord

    queryOperation.queryCompletionBlock = { [weak self] (cursor : CKQueryCursor!, error : NSError!) in

        if cursor != nil {
            println("there is more data to fetch")
            let newOperation = CKQueryOperation(cursor: cursor)
            newOperation.recordFetchedBlock = self!.fetchedARecord
            newOperation.queryCompletionBlock = queryOperation.queryCompletionBlock
            self!.privateDatabase?.addOperation(newOperation)
        }

    }

    privateDatabase?.addOperation(queryOperation)
}

var i = 0
func fetchedARecord (record: CKRecord!) {
    println("\(NSDate().timeIntervalSinceReferenceDate*1000) \(++i)")
}

【问题讨论】：

好的。我找到了这个。 stackoverflow.com/a/27135836/893771 。不过，一段代码会有很大帮助。
This answer to a similar question还展示了如何保持对queryOperation的强烈引用，以防止您的提取在不完整时结束。
此解决方案将导致操作仅运行 3 次！请改用：stackoverflow.com/a/31664231/530884

标签： ios swift nspredicate cloudkit ckquery

【解决方案1】：

100 是标准查询的默认限制。这个数额不是固定的。它可能因 iCloud 总负载而异。如果你想影响这个数量，那么你需要使用 CKQueryOperation 并像这样设置 resultsLimit： operation.resultsLimit = CKQueryOperationMaximumResults; CKQueryOperationMaximumResults 是默认值，并将其限制为 100（大部分时间）。不要将该值设置得太高。如果你想要更多的记录，那么使用queryCompletionBlock的游标继续读取更多的记录。

【讨论】：

伟大的埃德温。我之前链接到你的答案:)。你有任何示例代码如何做'光标'吗？这将为我节省一些时间。
抱歉，我没有准备好样板。但这并不难。你可以像这样开始一个新的 queryOperation： var operation = CKQueryOperation(cursor: cursor)
我接受了您的回答并使用示例代码更新了我的问题。 Tnx 老兄。
很好，但在 Objective C 中有这样的例子吗？
感谢@EdwinVermeer 的精彩讨论并提供示例代码@CPPChase！对于“newOperation.queryCompletionBlock = queryOperation.queryCompletionBlock”这一行，虽然感觉不是正确的方法，但我找不到更好的方法 - 想法？

【解决方案2】：

我在 Swift 4.2 中更新了 GuiSoySauce 的代码。

func cloudKitLoadRecords(result: @escaping (_ objects: [CKRecord]?, _ error: Error?) -> Void) {
    // predicate
    var predicate = NSPredicate(value: true)
    // query
    let cloudKitQuery = CKQuery(recordType: "recordType", predicate: predicate)

    // records to store
    var records = [CKRecord]()

    //operation basis
    let publicDatabase = CKContainer.defaultContainer().publicCloudDatabase

    // recurrent operations function
    var recurrentOperationsCounter = 101
    func recurrentOperations(cursor: CKQueryCursor?){
        let recurrentOperation = CKQueryOperation(cursor: cursor!)
        recurrentOperation.recordFetchedBlock = { (record:CKRecord!) -> Void in
            print("-> cloudKitLoadRecords - recurrentOperations - fetch \(recurrentOperationsCounter)")
            recurrentOperationsCounter += 1
            records.append(record)
        }
        recurrentOperation.queryCompletionBlock = { (cursor: CKQueryOperation.Cursor?, error: Error?) -> Void in
            if ((error) != nil) {
                print("-> cloudKitLoadRecords - recurrentOperations - error - \(String(describing: error))")
                result(nil, error)
            } else {
                if cursor != nil {
                    print("-> cloudKitLoadRecords - recurrentOperations - records \(records.count) - cursor \(cursor!.description)")
                    recurrentOperations(cursor: cursor!)
                } else {
                    print("-> cloudKitLoadRecords - recurrentOperations - records \(records.count) - cursor nil - done")
                    result(records, nil)
                }
            }
        }
        publicDatabase.add(recurrentOperation)
    }
    // initial operation
    var initialOperationCounter = 1
    let initialOperation = CKQueryOperation(query: cloudKitQuery)
    initialOperation.recordFetchedBlock = { (record:CKRecord!) -> Void in
        print("-> cloudKitLoadRecords - initialOperation - fetch \(initialOperationCounter)")
        initialOperationCounter += 1
        records.append(record)
    }
    initialOperation.queryCompletionBlock = { (cursor: CKQueryOperation.Cursor?, error: Error?) -> Void in
        if ((error) != nil) {
            print("-> cloudKitLoadRecords - initialOperation - error - \(String(describing: error))")
            result(nil, error)
        } else {
            if cursor != nil {
                print("-> cloudKitLoadRecords - initialOperation - records \(records.count) - cursor \(cursor!.description)")
                recurrentOperations(cursor: cursor!)
            } else {
                print("-> cloudKitLoadRecords - initialOperation - records \(records.count) - cursor nil - done")
                result(records, nil)
            }
        }
    }
    publicDatabase.add(initialOperation)
}

用法

cloudKitLoadRecords() { (records, error) -> Void in
    if let error = error {
        // do something
    } else {
        if let records = records {
            // do something
        } else {
            // do something
        }
    }
}

【讨论】：

我的问题是我将 recurrentOperation 完成块分配给与原始完成块相同的完成块，并且永远不会调用新的完成块。给 recurrentOperation 完成它自己的完成块为我修复了它。

【解决方案3】：

我在我的项目中使用此代码从记录类型中获取所有记录，它在目标 c 中。我使用“Entry”作为desiredKeys。

+ (void)fetchRecordsWithType:(NSString *)recordType
           completionHandler:(void (^)(NSArray *records, NSError *error))completionHandler {

    NSPredicate *truePredicate = [NSPredicate predicateWithValue:YES];

    CKQuery *query = [[CKQuery alloc] initWithRecordType:recordType
                                               predicate:truePredicate];

    CKQueryOperation *queryOperation = [[CKQueryOperation alloc] initWithQuery:query];
    queryOperation.desiredKeys = @[@"Entry"];

    NSMutableArray *results = [NSMutableArray new];

    queryOperation.recordFetchedBlock = ^(CKRecord *record) {

        [results addObject:record]; };

    queryOperation.queryCompletionBlock = ^(CKQueryCursor *cursor, NSError *error) {

        [self retrieveNextBatchOfQueryFromCursor:cursor
                                         results:results
                                           error:error
                               completionHandler:completionHandler]; };

    [[self CloudKitContainer].privateCloudDatabase addOperation:queryOperation]; }


+ (void)retrieveNextBatchOfQueryFromCursor:(CKQueryCursor *)cursor
                                   results:(NSMutableArray *)results
                                     error:(NSError *)error
                         completionHandler:(void (^)(NSArray *records, NSError *error))completionHandler {

    // CloudKit apparently has query limit

    if (cursor != nil
        && !error) {

        CKQueryOperation *nextOperation = [[CKQueryOperation alloc] initWithCursor:cursor];

        nextOperation.recordFetchedBlock = ^(CKRecord *record) {

            [results addObject:record]; };

        nextOperation.queryCompletionBlock = ^(CKQueryCursor *cursor, NSError *error) {

            [self retrieveNextBatchOfQueryFromCursor:cursor
                                             results:results
                                               error:error
                                   completionHandler:completionHandler]; };

        [[self CloudKitContainer].privateCloudDatabase addOperation:nextOperation]; }

    else {

        dispatch_async(dispatch_get_main_queue(), ^(void){

            completionHandler(results, error); }); }}

【讨论】：

【解决方案4】：

另一种在函数内部运行它的方法，它带有一个完成处理程序，在获取所有记录之前不会停止。这可以被应用程序中不同的不同视图控制器重复使用。

查询

func cloudKitLoadRecords(result: (objects: [CKRecord]?, error: NSError?) -> Void){

    // predicate
    var predicate = NSPredicate(value: true)

    // query
    let cloudKitQuery = CKQuery(recordType: "ClassName", predicate: predicate)

    // records to store
    var records = [CKRecord]()

    //operation basis
    let publicDatabase = CKContainer.defaultContainer().publicCloudDatabase

    // recurrent operations function
    var recurrentOperationsCounter = 101
    func recurrentOperations(cursor: CKQueryCursor?){
        let recurrentOperation = CKQueryOperation(cursor: cursor!)
        recurrentOperation.recordFetchedBlock = { (record:CKRecord!) -> Void in
            print("-> cloudKitLoadRecords - recurrentOperations - fetch \(recurrentOperationsCounter++)")
            records.append(record)
        }
        recurrentOperation.queryCompletionBlock = { (cursor:CKQueryCursor?, error:NSError?) -> Void in
            if ((error) != nil)
            {
                print("-> cloudKitLoadRecords - recurrentOperations - error - \(error)")
                result(objects: nil, error: error)
            }
            else
            {
                if cursor != nil
                {
                    print("-> cloudKitLoadRecords - recurrentOperations - records \(records.count) - cursor \(cursor!.description)")
                    recurrentOperations(cursor!)
                }
                else
                {
                    print("-> cloudKitLoadRecords - recurrentOperations - records \(records.count) - cursor nil - done")
                    result(objects: records, error: nil)
                }
            }
        }
        publicDatabase.addOperation(recurrentOperation)
    }

    // initial operation
    var initialOperationCounter = 1
    let initialOperation = CKQueryOperation(query: cloudKitQuery)
    initialOperation.recordFetchedBlock = { (record:CKRecord!) -> Void in
        print("-> cloudKitLoadRecords - initialOperation - fetch \(initialOperationCounter++)")
        records.append(record)
    }
    initialOperation.queryCompletionBlock = { (cursor:CKQueryCursor?, error:NSError?) -> Void in
        if ((error) != nil)
        {
            print("-> cloudKitLoadRecords - initialOperation - error - \(error)")
            result(objects: nil, error: error)
        }
        else
        {
            if cursor != nil
            {
                print("-> cloudKitLoadRecords - initialOperation - records \(records.count) - cursor \(cursor!.description)")
                recurrentOperations(cursor!)
            }
            else
            {
                print("-> cloudKitLoadRecords - initialOperation - records \(records.count) - cursor nil - done")
                result(objects: records, error: nil)
            }
        }
    }
    publicDatabase.addOperation(initialOperation)
}

用法

cloudKitLoadRecords() { (queryObjects, error) -> Void in
            dispatch_async(dispatch_get_main_queue()) {
                if error != nil
                {
                    // handle error
                }
                else
                {
                    // clean objects array if you need to
                    self.objects.removeAll()

                    if queryObjects!.count == 0
                    {
                        // do nothing
                    }
                    else
                    {   
                        // attach found objects to your object array
                        self.objects = queryObjects!
                    }
                }
            }
        }

【讨论】：

【解决方案5】：

Swift 最简单的例子：

func fetchServices(completion: ErrorHandler? = nil) {

    var records = [CKRecord]()

    let query = CKQuery(recordType: "Service", predicate: NSPredicate(value: true))
    let queryOperation = CKQueryOperation(query: query)

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

    queryOperation.queryCompletionBlock = { cursor, error in
        self.fetchServices(with: cursor, error: error, records: records, completion: completion)
    }

    database.add(queryOperation)
}

private func fetchServices(with cursor: CKQueryCursor?, error: Swift.Error?, records: [CKRecord], completion: ErrorHandler? = nil) {

    var currentRecords = records

    if let cursor = cursor, error == nil {

        let queryOperation = CKQueryOperation(cursor: cursor)
        queryOperation.recordFetchedBlock = { record in
            currentRecords.append(record)
        }

        queryOperation.queryCompletionBlock = { cursor, error in
            self.fetchServices(with: cursor, error: error, records: currentRecords, completion: completion)
        }

        database.add(queryOperation)

    } else {
        parseAndSaveServices(with: records, completion: completion)
    }
}

【讨论】：