CKQueryOperation获取最后一条记录

Question

我需要获取cloudkit中的最后一条记录。下面是我的代码：

 CKContainer *container = [CKContainer containerWithIdentifier:containerID];
    CKDatabase *publicDatabase = [container publicCloudDatabase];
    CKQuery *query = [[CKQuery alloc] initWithRecordType:recordType
                                               predicate:[NSPredicate predicateWithFormat:@"TRUEPREDICATE"]];
     CKQueryOperation *queryOp = [[CKQueryOperation alloc] initWithQuery:query];

    queryOp.desiredKeys = @[@"record.recordID.recordName"];
    queryOp.recordFetchedBlock = ^(CKRecord *record)
    {
        //do something
    };

     queryOp.queryCompletionBlock = ^(CKQueryCursor *cursor, NSError *error)
    {
        NSLog(@"CKQueryCursor  error %@", error);
    };

    queryOp.resultsLimit = CKQueryOperationMaximumResults;
    [publicDatabase addOperation:queryOp];

我的问题是，如何修改代码以获得cloudkit中的最后一条记录？

我将非常感谢你的帮助

Answer 1

你可以按创建日期升序排序，然后像这样要求1个结果(代码在Swift中)：

添加排序：

query.sortDescriptors = [NSSortDescriptor(key: "creationDate", ascending: false)]

限制结果：

queryOp.resultsLimit = 1

Answer 2

Objective-C版本

    NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:NO];
query.sortDescriptors = @[sortDescriptor];

对于一条记录：

queryOp.resultsLimit = 1;

Answer 3

设置resultsLimit似乎对我不起作用，但是无论如何都要设置它，并使用时间戳或记录创建日期对结果进行排序。然后将结果存储在数组中，并根据排序顺序使用第一项或最后一项

    CKContainer *container = [CKContainer containerWithIdentifier:containerID];
    CKDatabase *publicDatabase = [container publicCloudDatabase];
    CKQuery *query = [[CKQuery alloc] initWithRecordType:recordType predicate:[NSPredicate predicateWithFormat:@"TRUEPREDICATE"]];

    NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"creationDate" ascending:NO];
    query.sortDescriptors = @[sortDescriptor];

    CKQueryOperation *queryOp = [[CKQueryOperation alloc] initWithQuery:query];
    queryOp.desiredKeys = @[@"record.recordID.recordName"];
    queryOp.recordFetchedBlock = ^(CKRecord *record)
    {
        //do something
        recordArray.append(record)
    };

    queryOp.queryCompletionBlock = ^(CKQueryCursor *cursor, NSError *error)
    {
        NSLog(@"CKQueryCursor  error %@", error);
        let myLastRecord = recordArray[recordArray.count - 1]
    };

    queryOp.resultsLimit = CKQueryOperationMaximumResults;
    [publicDatabase addOperation:queryOp];