将完成块添加到 CloudKit 函数

Question

我的 ViewController 想要显示一些基于 CloudKit 查询的数据。

我的 CloudKit 代码全部在单独的 class 中。 class 有一个名为 loadExpenses() 的函数，它从 CK 获取一些费用实体。

我希望能够从 VC 调用 loadExpenses()，因此我需要函数提供的完成块来从 VC 更新 UI。

这就是 loadExpenses() 的样子：

func loadExpenses() {
    let pred = NSPredicate(value: true)
    let sort = NSSortDescriptor(key: "creationDate", ascending: true)
    let query = CKQuery(recordType: "Expense", predicate: pred)
    query.sortDescriptors = [sort]

    let operation = CKQueryOperation(query: query)
    operation.desiredKeys = ["person", "action", "amount", "timestamp"]
    operation.resultsLimit = 50

    var newExpenses = [Expense]()

    operation.recordFetchedBlock = { (record) in
        let recordID = record.recordID
        let person = record["person"] as! String
        let action = record["action"] as! String
        let amount = record["amount"] as! Double
        let timestamp = record["timestamp"] as! NSDate
        let expense = Expense(person: person, action: action, amount: amount, timestamp: timestamp)
        newExpenses.append(expense)
    }

    // This is the part that needs to be changed
    operation.queryCompletionBlock = { [unowned self] (cursor, error) in
        dispatch_async(dispatch_get_main_queue()) {
            if error == nil {
                self.objects = newExpenses
                self.tableView.reloadData()
                self.refreshRealmDataFromCK()
            } else {
                let ac = UIAlertController(title: "Fetch failed", message: "There was a problem fetching the list of expenses; please try again: \(error!.localizedDescription)", preferredStyle: .Alert)
                ac.addAction(UIAlertAction(title: "OK", style: .Default, handler: nil))
                self.presentViewController(ac, animated: true, completion: nil)
            }
        }
    }
    CKContainer.defaultContainer().privateCloudDatabase.addOperation(operation)
}

显然最后一部分不会执行，考虑到所有那些 self.property 都属于 VC（我保留它们只是为了展示我需要在 VC 中做什么） .

如我所说，我希望能够从 VC 和 get/use 完成块中调用此函数来更新这些属性。我该怎么做？

Answer 1

您需要将块作为参数传递给 loadExpenses() 函数。所以它实际上应该被定义为 loadExpenses(completionBlock:([whatever parameters you need in here])->Void).

然后，您可以从 operation.queryCompletionBlock 块中调用传递的 completionBlock 块（使用适当的参数）。

编辑：

所以这当然没有经过测试，但您可以试一试：

func loadExpenses(completionBlock:([Expense])->Void) {
    let pred = NSPredicate(value: true)
    let sort = NSSortDescriptor(key: "creationDate", ascending: true)
    let query = CKQuery(recordType: "Expense", predicate: pred)
    query.sortDescriptors = [sort]

    let operation = CKQueryOperation(query: query)
    operation.desiredKeys = ["person", "action", "amount", "timestamp"]
    operation.resultsLimit = 50

    var newExpenses = [Expense]()

    operation.recordFetchedBlock = { (record) in
        let recordID = record.recordID
        let person = record["person"] as! String
        let action = record["action"] as! String
        let amount = record["amount"] as! Double
        let timestamp = record["timestamp"] as! NSDate
        let expense = Expense(person: person, action: action, amount: amount, timestamp: timestamp)
        newExpenses.append(expense)
    }

    // This is the part that needs to be changed
    operation.queryCompletionBlock = { [unowned self] (cursor, error) in
        completionBlock(newExpenses)
    }
    CKContainer.defaultContainer().privateCloudDatabase.addOperation(operation)
}

然后这样称呼它：

loadExpenses({ (newExpenses:[Expense]) -> Void in {
    dispatch_async(dispatch_get_main_queue()) {
        if error == nil {
            self.objects = newExpenses
            self.tableView.reloadData()
            self.refreshRealmDataFromCK()
        } else {
            let ac = UIAlertController(title: "Fetch failed", message: "There was a problem fetching the list of expenses; please try again: \(error!.localizedDescription)", preferredStyle: .Alert)
            ac.addAction(UIAlertAction(title: "OK", style: .Default, handler: nil))
            self.presentViewController(ac, animated: true, completion: nil)
        }
    }
}

将完成块添加到 CloudKit 函数

Adding a completion block to a CloudKit function

swift

cloudkit

completion-block