如何在Swift中清除SFSafariViewController的cookie

Question

我正在尝试在Swift中清除SFSafariViewController的cookie并使用这行代码。它可以清除WebView cookie，但对SFSafariViewController无效。

@IBAction  func clearAct(sender: AnyObject) {

    let storage = NSHTTPCookieStorage.sharedHTTPCookieStorage()
    for cookie in storage.cookies! {
        storage.deleteCookie(cookie)
    }
    NSUserDefaults.standardUserDefaults().synchronize()
}