Defines the presentation style that will be used for this view controller when it is presented modally. Set this property on the view controller to be presented, not the presenter.
 If this property has been set to UIModalPresentationAutomatic, reading it will always return a concrete presentation style. By default UIViewController resolves UIModalPresentationAutomatic to UIModalPresentationPageSheet, but other system-provided view controllers may resolve UIModalPresentationAutomatic to other concrete presentation styles.
 Defaults to UIModalPresentationAutomatic on iOS starting in iOS 13.0, and UIModalPresentationFullScreen on previous versions. Defaults to UIModalPresentationFullScreen on all other platforms.


public enum UIModalPresentationStyle : Int {
  case fullScreen
  
  @available(iOS 3.2, *)
  case pageSheet
  @available(iOS 3.2, *)
  case formSheet

  @available(iOS 3.2, *)
  case currentContext

  @available(iOS 7.0, *)
  case custom

  @available(iOS 8.0, *)
  case overFullScreen

  @available(iOS 8.0, *)
  case overCurrentContext

  @available(iOS 8.0, *)
  case popover

  
  @available(iOS 7.0, *)
  case none

  @available(iOS 13.0, *)
  case automatic
}

// UITextField 的 _placeholderLabel
    let textField = UITextField.init()
    textField.setValue(UIColor.red, forKey: "_placeholderLabel.textColor")
    
    /// UISearchBar 的 _searchField
    [searchBar valueForKey:@"_searchField"]

///分別設置字體大小和顏色（富文本）
textField.attributedPlaceholder = NSAttributedString.init(string: "請輸入....", attributes: [NSAttributedString.Key.foregroundColor: UIColor.red], [NSAttributedString.Key.font: UIFont.systemFont(ofSize: 15)])

 /// UISearchBar 用 searchField代替
bar.value(forKey: "searchField") as! UITextField

// 只有等執行完 UIViewController 的 viewDidAppear 方法以后，才能獲取到正確的值，在viewDidLoad等地方 frame Size 為 0，例如：
 UIApplication.shared.statusBarFrame

@available(iOS, introduced: 2.0, deprecated: 12.0, message: "No longer supported; please adopt WKWebView.")
open class UIWebView : UIView, NSCoding, UIScrollViewDelegate {
	.........
	.........
	.........
}

- (NSString*) getWifiSsid {
  if (@available(iOS 13.0, *)) {
    //用戶明確拒絕，可以彈窗提示用戶到設置中手動打開權限
    if ([CLLocationManager authorizationStatus] == kCLAuthorizationStatusDenied) {
      NSLog(@"User has explicitly denied authorization for this application, or location services are disabled in Settings.");
      //使用下面接口可以打開當前應用的設置頁面
      //[[UIApplication sharedApplication] openURL:[NSURL URLWithString:UIApplicationOpenSettingsURLString]];
      return nil;
    }
    CLLocationManager* cllocation = [[CLLocationManager alloc] init];
    if(![CLLocationManager locationServicesEnabled] || [CLLocationManager authorizationStatus] == kCLAuthorizationStatusNotDetermined){
      //彈框提示用戶是否開啟位置權限
      [cllocation requestWhenInUseAuthorization];
      usleep(50);
      //遞歸等待用戶選選擇
      return [self getWifiSsidWithCallback:callback];
    }
  }
  NSString *wifiName = nil;
  CFArrayRef wifiInterfaces = CNCopySupportedInterfaces();
  if (!wifiInterfaces) {
    return nil;
  }
  NSArray *interfaces = (__bridge NSArray *)wifiInterfaces;
  for (NSString *interfaceName in interfaces) {
    CFDictionaryRef dictRef = CNCopyCurrentNetworkInfo((__bridge CFStringRef)(interfaceName));

    if (dictRef) {
      NSDictionary *networkInfo = (__bridge NSDictionary *)dictRef;
      NSLog(@"network info -> %@", networkInfo);
      wifiName = [networkInfo objectForKey:(__bridge NSString *)kCNNetworkInfoKeySSID];
      CFRelease(dictRef);
    }
  }
  CFRelease(wifiInterfaces);
  return wifiName;
}

 network info -> {
BSSID = "44:dd:fb:43:91:ff";
SSID = "Asus_c039";
SSIDDATA = <41737573 5f633033 39>;
}
不同意
network info -> {
BSSID = "00:00:00:00:00:00";
SSID = WLAN;
SSIDDATA = <574c414e>;
}