Question

所以，我正在做一个异步查询，返回多个Worker对象，每个Worker与WorkerPeriod有关系，我使用这个关系进行查询，问题是，查询是异步的，当它返回时从Web服务中，workerIndex搞砸了

 workerQuery.whereKey("construction", equalTo: currentConstruction).findObjectsInBackgroundWithBlock({ (unsafeWorkers, error) -> Void in
            guard let workers = unsafeWorkers as? [Worker] where error == nil && workers.count == 0 else {
                return
            }

            for var workerIndex = 0; workerIndex < workers.count; workerIndex++ {

                let currentWorker = workers[workerIndex]


                if let periodQuery = WorkerPeriod.query() {
                    periodQuery.whereKey("worker", equalTo: currentWorker)

                    let weakWorkerIndex = workerIndex
                    print("weakWorkerIndex = \(weakWorkerIndex) worker \(workerIndex)")
                    periodQuery.findObjectsInBackgroundWithBlock({ (unsafeWorkerPeriod, error) -> Void in

                        guard let workerPeriods = unsafeWorkerPeriod as? [WorkerPeriod] where error == nil && workerPeriods.count != 0 else {
                            return
                        }
                        print("block weakWorkerIndex = \(weakWorkerIndex) workerIndex \(workerIndex)")

                        .
                        .

                    })
                }
            }

我尝试创建一个“weakWorkerIndex”作为let来保存值，就像我们在Objective-C中使用__block变量一样，但这不起作用，块交互只是忽略了值，你可以看到在输出中：

weakWorkerIndex = 0 worker 0
weakWorkerIndex = 1 worker 1
block weakWorkerIndex = 0 workerIndex 2
block weakWorkerIndex = 0 workerIndex 2
block weakWorkerIndex = 0 workerIndex 2

顺便说一句：我删除了任何不必要的代码以简化阅读。

Answer 1

在完成处理程序中，您需要确保{<1}}按值捕获，例如：

workerIndex

请参阅Swift Capture Lists

在Swift 2.1中阻止存储的var

1 个答案: