小编Jul*_*ien的帖子

我一直在使用以下帖子作为如何显示UIAlertController与特定无关的from代码的指导UIViewController。现在，我要对该代码进行单元测试：

func showAlert(alert: UIAlertController, animated: Bool, completion: (()->Void)?) 
{
    let alertWindow = UIWindow(frame: UIScreen.mainScreen().bounds)

    // Keep a strong refence to the window. 
    // We manually set this to nil when the alert is dismissed
    self.alertWindow = alertWindow

    alertWindow.rootViewController = UIViewController()        
    if let currentTopWindow = UIApplication.sharedApplication().windows.last {
        alertWindow.windowLevel = currentTopWindow.windowLevel + 1
    }
    else {
        // This case only happens during unit testing
        Logger.trace(ICELogLevel.Error, category: .Utility, message: "The application doesn't have a window being displayed!") …

我的应用程序中有一个视图控制器，用于调试目的以显示应用程序的一些内部结构（仅适用于本地 xcode 版本，应用程序商店版本没有此控制器）。

在此控制器中，我有一个标签，我想反映内部组件的状态（具体来说，我希望它显示该组件是启用还是禁用）。

我的问题：

.attributedText#1：将UILabel 的属性设置为与之前相同的值是否昂贵，或者我应该缓存旧值并仅在属性更改时设置该属性？

.text#2：（非归属）财产怎么样？

我目前正在使用以下代码：

// Schedule timer to update the control panel. (This is debug-only, so not worth
// the complexity of making this event-based)
Timer.scheduledTimer(withTimeInterval: 0.5,
                 repeats: true) { [weak self] timer in

    DispatchQueue.main.async {

        // Stop timer if we've been dealloced or are no longer being presented
        guard let strongSelf = self,
              strongSelf.isBeingPresented else
        {
            timer.invalidate()
            return
        }

        // "Something Enabled / Disabled" label
        let somethingIsEnabled = strongSelf.someDepenency.isEnabled
        let somethingEnabledString = …