IBAction的關鍵值編碼符合性錯誤

Question

免責聲明：忽略使用此產品的生產應用程序可能會或可能不會通過審覈的事實。我只是想讓這個概念起作用。下面是我試圖執行的代碼，我試圖做的所有代碼（現在）都是初始化四個常量，並且在第三個常量上有困難。

let app = UIApplication.shared 
let statusBar = app.value(forKey: "statusBar") as AnyObject 
let foregroundView = statusBar.value(forKey: "foregroundView") as AnyObject 
let subviews = Array(foregroundView.subviews) 

給出錯誤：

*** Terminating app due to uncaught exception 'NSUnknownKeyException', reason: '[<_SwiftValue 0x170087850> valueForUndefinedKey:]: this class is not key value coding-compliant for the key foregroundView.' 

需要注意的是，不同於當應用程序被運行中發生的大多數其他鍵值合規性的錯誤，我的執行IBAction爲當（通過UIButton的觸發）只發生它有四行代碼。

作爲參考，我試圖實現什麼this post在Objective-C中描述。我對Swift很陌生，但我想我已經正確地翻譯了它。

整個func是在這裏：

@IBAction func getSignal(_ sender: UIButton) { 

    let app = UIApplication.shared 
    let statusBar = app.value(forKey: "statusBar") as AnyObject 
    let foregroundView = statusBar.value(forKey: "foregroundView") as AnyObject 
    let subviews = Array(foregroundView.subviews) 
    var dataNetworkItemView: UIView? 
    for subview in subviews { 
     if (subview as AnyObject).isKind(of: NSClassFromString("UIStatusBarSignalStrengthItemView")!) { 
      dataNetworkItemView = subview 
      break 
     } 
    } 
    let signalStrength = (dataNetworkItemView?.value(forKey: "signalStrengthRaw") as? NSString)?.intValue 
    print("signal \(signalStrength)") 
} 

我從原始代碼塊，這裏轉換：

UIApplication *app = [UIApplication sharedApplication]; 
    NSArray *subviews = [[[app valueForKey:@"statusBar"]  valueForKey:@"foregroundView"] subviews]; 
    NSString *dataNetworkItemView = nil; 
    for (id subview in subviews) { 
     if([subview isKindOfClass:[NSClassFromString(@"UIStatusBarSignalStrengthItemView") class]]) 
     { 
      dataNetworkItemView = subview; 
      break; 
     } 
    } 
    int signalStrength = [[dataNetworkItemView valueForKey:@"signalStrengthRaw"] intValue]; 
    NSLog(@"signal %d", signalStrength); 

沒有編譯時錯誤或警告，和I」如何繼續下去。謝謝。

Answer 1

工作的Xcode 8個β，夫特3.0代碼：

let app = UIApplication.shared 
let statusBar = app().value(forKey: "statusBar")! as AnyObject 
let foregroundView = statusBar.value(forKey: "foregroundView")! as AnyObject 
let subviews = Array(foregroundView.subviews) 
var dataNetworkItemView: UIView? 
for subview in subviews { 
    if (subview as AnyObject).isKind(of: NSClassFromString("UIStatusBarSignalStrengthItemView")!) { 
     dataNetworkItemView = subview 
     break 
    } 
} 
let signalStrength = (dataNetworkItemView?.value(forKey: "signalStrengthRaw") as? NSString)?.intValue 
print("signal \(signalStrength)") 

的OP使用的Xcode 8 GM的，因此一個變化 - app()到app：

let statusBar = app.value(forKey: "statusBar")! as AnyObject