1.在storyboard里创建一个ViewController

2.写入如下代码

            print("弹出登录框")
            let loginViewController  = self.storyboard?.instantiateViewControllerWithIdentifier("login_view") as! LoginViewController
            presentViewController(loginViewController, animated: true, completion: nil)

3.LoginViewController.swift

import UIKit

class LoginViewController: UIViewController {
    
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
    }
    
    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
        // Dispose of any resources that can be recreated.
    }
    
    
}

4.关闭

self.dismissViewControllerAnimated(true, completion: nil)

结束