-1

如果我从服务器得到某个响应,我只想执行一个 segue。迅速,我怎么能等到我得到回复才能继续?

4

1 回答 1

1

最重要的是,您不会“等待”响应,而是简单地指定响应到来时您希望发生的事情。例如,如果您想在完成某些网络请求时执行 segue,您应该使用完成处理程序模式。

这里的问题是您可能习惯于将您的 UI 控件与 Interface Builder 中的 segue 挂钩。在我们的例子中,我们不想这样做,而是想要执行网络请求,然后让它的完成处理程序以编程方式调用 segue。因此,我们必须创建一个可以以编程方式执行的 segue,然后将您的按钮连接到@IBAction执行网络请求的按钮上,如果合适的话,以编程方式执行 segue。但是,请注意,不应该直接连接到按钮的 segue。我们将以编程方式进行。

例如:

  1. control通过从第一个场景上方栏中的视图控制器图标拖动到第二个场景,将 segue 定义为两个视图控制器之间:

    在此处输入图像描述

  2. 通过选择 segue 并转到“Attributes Inspector”选项卡,为该 segue 提供故事板标识符:

    在此处输入图像描述

  3. 将按钮(或任何会触发此 segue 的东西)连接到@IBAction.

    在此处输入图像描述

  4. 编写一个@IBAction执行网络请求,并在完成后以编程方式调用该 segue:

    @IBAction func didTapButton(_ sender: Any) {
        let request = URLRequest(...).       // prepare request however your app requires
    
        let waitingView = showWaitingView()  // present something so that the user knows some network request is in progress
    
        // perform network request
    
        let task = URLSession.shared.dataTask(with: request) { data, response, error in
            // regardless of how we exit this, now that request is done, let's 
            // make sure to remove visual indication that network request was underway
    
            defer {
                DispatchQueue.main.async {
                    waitingView.removeFromSuperview()
                }
            }
    
            // make sure there wasn't an error; you'll undoubtedly have additional
            // criteria to apply here, but this is a start
    
            guard let data = data, error == nil else {
                print(error ?? "Unknown error")
                return
            }
    
            // parse and process the response however is appropriate in your case, e.g., if JSON:
            //
            // guard let responseObject = try? JSONSerialization.jsonObject(with data) else {
            //     // handle parsing error here
            //     return
            // }
            //
            // // do whatever you want with the parsed JSON here
    
            // do something with response
    
            DispatchQueue.main.async {
                performSegue(withIdentifier: "SegueToSceneTwo", sender: self)
            }
        }
        task.resume()
    }
    
    /// Show some view so user knows network request is underway
    ///
    /// You can do whatever you want here, but I'll blur the view and add `UIActivityIndicatorView`.
    
    private func showWaitingView() -> UIView {
        let effectView = UIVisualEffectView(effect: UIBlurEffect(style: .Dark))
        effectView.translatesAutoresizingMaskIntoConstraints = false
        view.addSubview(effectView)
        NSLayoutConstraint.activateConstraints([
            effectView.leadingAnchor.constraintEqualToAnchor(view.leadingAnchor),
            effectView.trailingAnchor.constraintEqualToAnchor(view.trailingAnchor),
            effectView.topAnchor.constraintEqualToAnchor(view.topAnchor),
            effectView.bottomAnchor.constraintEqualToAnchor(view.bottomAnchor)
        ])
    
        let spinner = UIActivityIndicatorView(activityIndicatorStyle: .WhiteLarge)
        effectView.addSubview(spinner)
        spinner.translatesAutoresizingMaskIntoConstraints = false
        NSLayoutConstraint.activateConstraints([
            spinner.centerXAnchor.constraintEqualToAnchor(view.centerXAnchor),
            spinner.centerYAnchor.constraintEqualToAnchor(view.centerYAnchor)
        ])
        spinner.startAnimating()
    
        return effectView
    }
    
于 2016-07-27T18:15:46.547 回答