Question

我正在构建一个应用程序，允许用户从公共商店上传/下载信息。我认为cloudKit存储将是理想的。

我希望用户能够通过KeyWord字段搜索商店中的记录，然后在选择一个记录时下载整个记录。

在SQL术语中，这将是：

SELECT id,KeyWords from myDB WHERE KeyWords LIKE %searchstring%

其次是：

SELECT * FROM myDB WHERE id = selectedID

我一直在使用此代码模式从cloudKit存储中检索记录：

var publicDatabase: CKDatabase?
let container = CKContainer.defaultContainer()

override func viewDidLoad() {
    super.viewDidLoad()
    publicDatabase = container.publicCloudDatabase
}

func performQuery(){
    let predicate = NSPredicate(value: true)
    let query = CKQuery(recordType: "Library", predicate: predicate)
    publicDatabase?.performQuery(query, inZoneWithID: nil,
        completionHandler: ({results, error in

        ...
        [code to handle results / error here]
        ...
    })
}

但是这会返回所有每条记录的内容，这是很多不必要的信息。

我只想从cloudkit记录中获取单个字段。

有没有一种简单的方法可以做到这一点，是否有人有代码片段？

CKFetchRecordsOperation允许下载受限制的列，但要求您知道要下载的记录的ID。

Answer 1

为此，您可以在CKQueryOperation上使用desiredKeys属性。有关详细信息，请参阅：desiredkeys documentation

Answer 2

确定有用的东西。这可能是hacky，但是我在相同的情况下为其他任何人提供信息......

let predicate = NSPredicate(value: true) // returns all - replace with whatever condition you want
let query = CKQuery(recordType: "Library", predicate: predicate) // create a query using the predicate
var operation = CKQueryOperation(query: query) // create an operation using the query
operation.desiredKeys = ["KeyWords"] // Array of whatever 'columns' you want to return
// operation.resultsLimit = 15 // optional limit on records

// Define a closure for what to do for each returned record
operation.recordFetchedBlock = { [weak self] (record:CKRecord!) in

    // Do whatever you want with each returned record  
    println(record.objectForKey("KeyWords"))

}

// Define a closure for when the operation is complete
operation.queryCompletionBlock = { [weak self] (cursor:CKQueryCursor!, error:NSError!) in

        if cursor != nil {
            // returns the point where the operation left off if you want t retrieve the rest of the records
        }

        dispatch_async(dispatch_get_main_queue(), { () -> Void in

            // Do what you want when process complete
            self!.tableView.reloadData()
            if error != nil {
                println("there was an error")
            }
        })
    }

self.publicDatabase!.addOperation(operation) // Perform the operation on given database

用于从cloudkit

2 个答案: