在块内分配值的引用变量

Question

您对完成块中分配给外部ref变量的值的范围有什么困惑。例如，在下面的代码中，operationError和savedRecords的值将在完成块之外保留。

    func applyLocalChangesToServer(insertedOrUpdatedCKRecords:Array<CKRecord>,deletedCKRecordIDs:Array<CKRecordID>) throws
    {
        var savedRecords:[CKRecord]?
        var conflictedRecords:[CKRecord] = [CKRecord]()
        var removeRecords:[CKRecord] = [CKRecord]()
        var operationError : NSError?

        let ckModifyRecordsOperation = CKModifyRecordsOperation(recordsToSave:insertedOrUpdatedCKRecords, recordIDsToDelete: deletedCKRecordIDs);
        ckModifyRecordsOperation.atomic = true
        ckModifyRecordsOperation.modifyRecordsCompletionBlock = ({(savedRecords1,deletedRecordIDs1,error)->Void in

            operationError = error

            if error == nil
            {
                wasSuccessful = true
                savedRecords = savedRecords1
            }
            else
            {
                wasSuccessful = false
                savedRecords = nil
                errorCKS = self.handleError(error!)
            }

        })
        ckModifyRecordsOperation.perRecordCompletionBlock = ({(ckRecord,error)->Void in

            if error != nil
            {  
                if error!.code == CKErrorCode.ServerRecordChanged.rawValue
                {
                    conflictedRecords.append(ckRecord!)
                }
            }

        })

        self.operationQueue?.addOperation(ckModifyRecordsOperation)
        self.operationQueue?.waitUntilAllOperationsAreFinished()

        if conflictedRecords.count > 0  
        {
            //Do work here

        }
        else if operationError != nil //Other then the partial error
        {
            throw operationError
        }

}

注意：由于func applyLocalChangesToServer抛出错误并且在while循环中，因此分配了operationError。

Answer 1

您的假设是正确的，在执行完成处理程序后，将在机箱范围中违反这些变量。所以你的代码应该按预期工作。

您还可以使用以下内容：

ckModifyRecordsOperation.main()

而不是：

self.operationQueue?.addOperation(ckModifyRecordsOperation)
self.operationQueue?.waitUntilAllOperationsAreFinished()

希望它有所帮助。