如果你想在按下按钮后转换到另一个ViewController，你可以用两种方法来完成：
1)present(_:animated:completion:)

@objc func buttonAction(sender: UIButton!) {
    let vc = self.storyboard?.instantiateViewController(withIdentifier: "Main") as! SecondViewController
    self.present(vc, animated: true, completion: nil)
}

2)pushViewController(_:animated:)

@objc func buttonAction(sender: UIButton!) {
    let vc = self.storyboard?.instantiateViewController(withIdentifier: "Main") as! SecondViewController
    self.navigationController?.pushViewController(vc, animated: true)
}

有三种方法可以显示新的视图控制器：
1.显示视图控制器：

@objc func buttonAction(sender: UIButton!) {
    let destinationVC = self.storyboard?.instantiateViewController(withIdentifier: "DestinationViewController") as! DestinationViewController
    self.present(destinationVC, animated: true, completion: nil)
}

1.从故事板中执行一个Segue：
如果你已经有了你想要在情节串联图板中呈现的视图控制器，并且它有一个从你的源VC到你的目标VC的segue，那么你可以添加一个标识符到segue并这样做。

@objc func buttonAction(sender: UIButton!) {
         self.performSegue(withIdentifier: "MySegueIdentifier", sender: self)
    }

1.将视图控制器推到堆栈上（这仅在原始VC嵌入到导航控制器中时有效）：

@objc func buttonAction(sender: UIButton!) {
    let destinationVC = self.storyboard?.instantiateViewController(withIdentifier: "DestinationViewController") as! DestinationViewController
    self.navigationController?.pushViewController(destinationVC, animated: true)
}