Application tried to push a nil view controller on target

1.原因：

采用self.storyboard时，获得的storyboard对象为空

2.修改方法：

初始化一个storyboard对象，然后使用这个对象获得相应的viewcontroller；

3.实例

UIStoryboard *stroyboard = [UIStoryboard   storyboardWithName:@"XXX"bundle:nil];

PhoneRegisterController *infoVC = [stroyboard   instantiateViewControllerWithIdentifier:@"PhoneRegisterControllerID"];

[self.navigationController  pushViewController:prVCanimated:YES];