Question

所以我有这个自定义导航栏项目，我想将其子类化并在其他ViewControllers中使用。问题是，条形码项目还有一个observer，我想在ViewDidAppear添加observer并移除ViewDidDisappear上的subclass。如何observer条形项目和ViewControllers输出。并将其包含在我的每个ViewController中，而不是复制代码？

当前代码：

在每个override func viewWillAppear(animated: Bool) { if (!observingDefaults) { defaults.addObserver(self, forKeyPath: Constants.General.kConnectedToPC, options: NSKeyValueObservingOptions(), context: nil) observingDefaults = true } self.updateConnectionIcon() } override func viewWillDisappear(animated: Bool) { super.viewWillDisappear(animated) if (observingDefaults) { defaults.removeObserver(self, forKeyPath: Constants.General.kConnectedToPC) observingDefaults = false } }中：

extension UIViewController {

func updateConnectionIcon() {
    self.navigationItem.rightBarButtonItem = nil

    let isConnected = NSUserDefaults.standardUserDefaults().boolForKey(Constants.General.kConnectedToPC)

    let button = UIButton()

    if isConnected {
        button.setImage(UIImage(named: "BluetoothEnabled")?.imageWithRenderingMode(.AlwaysTemplate), forState: UIControlState.Normal)
    } else {
        button.setImage(UIImage(named: "BluetoothDisabled")?.imageWithRenderingMode(.AlwaysTemplate), forState: UIControlState.Normal)
    }

    button.frame = CGRectMake(0, 0, 23, 31)
    button.tintColor = UIColor.whiteColor()
    button.userInteractionEnabled = false
    let barButton = UIBarButtonItem(customView: button)
    self.navigationItem.rightBarButtonItem = barButton
}
}

导航条项目的扩展名：

ViewController

无论如何，我可以将上半部分添加到底部代码，这样我就可以在每个class PercentageFile: def __init__(self, filename): self.size = os.stat(filename)[6] self.f = open(filename,"r") self.i = self.f.tell() def __enter__(self): return self def readline(self): data = self.f.readline() self.i = self.f.tell() return data def __iter__(self): return self def __next__(self): data = self.f.readline() if self.i == self.f.tell(): raise StopIteration self.i = self.f.tell() return data def read(self, size=None): if size is None: self.i = self.size return self.f.read() data = self.f.read(size) self.i = self.f.tell() return data @property def percentage(self): return float(self.i) / self.size * 100.0 def __exit__(self, exc_type, exc_value, traceback): self.f.close()中调用updateConnectionIcon（）？

Answer 1

不是将观察者放在每个viewController中，而是创建一个BaseClase并将其保留在那里并继承所有需要这些观察者的类。这有道理吗？

带观察者的Swift自定义导航栏项目

1 个答案: