Question

我想在正在执行的所有操作完成后释放NSOperationQueue。到目前为止，我已在下面进行了编码，但据我所知，waitUntilAllOperationsAreFinished是异步调用，无法保持我的operationQueue为零。

- (void)deallocOperationQueue
{
    [operationQueue waitUntilAllOperationsAreFinished];
    operationQueue = nil;
}

Answer 1

引用Avi

您不需要等待所有操作完成。刚设置当你完成它时，operationQueue为nil。如果队列仍然有操作，没有任何反应;他们仍然会完成。

- (void)deallocOperationQueue
{
    operationQueue = nil;
}

我已经测试了代码并确认所声明的行为确实发生了。

Answer 2

您可以对NSOperationQueue进行子类化并观察操作键路径，直到它达到零：

class DownloadOperationQueue: NSOperationQueue {

    private static var operationsKeyPath: String {
        return "operations"
    }

    deinit {
        self.removeObserver(self, forKeyPath: "operations")
    }

    var completionBlock: (() -> Void)? {
        didSet {
            self.addObserver(self, forKeyPath: DownloadOperationQueue.operationsKeyPath, options: .New, context: nil)
        }
    }

    override init() {
        super.init()
    }

    override func observeValueForKeyPath(keyPath: String?, ofObject object: AnyObject?, change: [String : AnyObject]?, context: UnsafeMutablePointer<Void>) {
        if let operationPath = keyPath where operationPath == DownloadOperationQueue.operationsKeyPath {
            if self.operations.count == 0 {
                NSOperationQueue.mainQueue().addOperationWithBlock({ 
                    self.completionBlock?()
                })
            }
        }
    }

}

完成后：

var operationQueue: DownloadOperationQueue? = DownloadOperationQueue()

// Add your operations ...

operationQueue?.completionBlock = {
    operationQueue = nil
}

队列中的所有操作完成后立即释放NSOperationQueue

2 个答案: