具有自定义大小的PresentViewController

Question

我在objective-c中有这个旧代码，它在自定义框架中的当前视图中显示一个视图控制器：

UIStoryboard *storyboard = [UIStoryboard storyboardWithName:@"Main" bundle:nil];

    UIViewController *viewController;

    viewController = nil;
    PopoverChoiseTableViewController *viewControllers = (PopoverChoiseTableViewController *)[storyboard instantiateViewControllerWithIdentifier:@"modalPopoverChoise"];

    viewController = viewControllers;
    [self.navigationController.navigationBar setUserInteractionEnabled:NO];

    viewController.modalPresentationStyle = UIModalPresentationOverCurrentContext;

    [self presentViewController:viewController animated:NO completion:^{
        viewController.view.superview.frame = CGRectMake(0, 0, 200, 255);
        viewController.view.superview.center = self.view.center;
        viewController.view.layer.cornerRadius = 5;
        viewController.view.layer.masksToBounds = YES;
    }];

我试图在swift中做同样的事情：

        let storyboard = UIStoryboard(name: "Main", bundle: nil)
        let vc = storyboard.instantiateViewControllerWithIdentifier(identifier)
        vc.modalPresentationStyle = UIModalPresentationStyle.PageSheet
        self.presentViewController(vc, animated: true, completion: nil)

        vc.view.superview?.frame = CGRectMake(0, 0, 200, 255)
        vc.view.superview?.center = self.view.center
        vc.view.layer.cornerRadius = 5
        vc.view.layer.masksToBounds = true

此代码的问题是我的视图框以全屏模式打开，而不是以设置尺寸（200x255）打开。

我该如何解决这个问题？