1.如果vc都是通过xib来生成的，没什么问题，但是如果只是直接init生成的话，UIViewController会在loadview的时候自动创建一个view，赋值给vc的view，但是NSViewController不会自动创建view，需要自己在loadview中创建view。如果NSViewController不创建view的话，虽然走了loadview方法，但是由于（Called after the view has been loaded.）self.view没有被创建，所以导致viewDidLoad不会被创建！
/* Called after the view has been loaded. For view controllers created in code, this is after -loadView. For view controllers unarchived from a nib, this is after the view is set. Default does nothing.
*/
- (void)viewDidLoad NS_AVAILABLE_MAC(10_10);
未完待续......
