UIStatusBar、UINavigationBarの高さを取得する

StatusBarの高さ

let statusBarHeight = UIApplication.sharedApplication().statusBarFrame.size.height

navigationBarの高さ

func navigationBarHeight(callFrom: UIViewController) -> CGFloat? {
    return callFrom.navigationController?.navigationBar.frame.size.height
}

Viewに関する情報を集約したManagerクラス/構造体で管理するのが良いかと思います

struct ViewManager {
    
    static let rootViewController = UIApplication.sharedApplication().keyWindow?.rootViewController
    
    static let statusBarHeight = UIApplication.sharedApplication().statusBarFrame.size.height
    
    static var currentWindow: UIWindow? {
        if let window = UIApplication.sharedApplication().keyWindow {
            return window
        } else {
            return UIApplication.sharedApplication().windows[0] as? UIWindow
        }
    }

    // デフォルトFloat(44)としてUnwrap
    static func navigationBarHeight(callFrom: UIViewController) -> CGFloat {
        return callFrom.navigationController?.navigationBar.frame.size.height ?? 44
    }
}