Unbalanced calls to begin/end appearance transitions for <YZPMainViewController: 0x7fa04b4970f0>.
Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: 'Application tried to present modally an active controller <UINavigationController: 0x7fd65a80ce00>.'
在ViewController中添加模态视图或者push时会报上面的错误,应该在viewDidAppear中调用