登陆成功后,跳转到主页面,需要隐藏后退回登陆页面的按钮
let vc:UIViewController=self.storyboard?.instantiateViewControllerWithIdentifier("view name") as!UIViewController
//先隐藏回退按钮,然后push 否则无效
vc.navigationItem.hidesBackButton=true
self.navigationController?.pushViewController(vc,animated:true)