从xib加载view和从xib加载ViewController

1.从xib加载ViewController 

（1）调用CustomerVC *vc =[[CustomerVC alloc] initWithNibName:@"CustomerVC" bundle:[NSBundle mainBundle]];

会调用-(instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

（2）CustomerVC *vc = [[CustomerVC alloc] init];

会先调用-(instancetype)init然后调用-(instancetype)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil

2.从xib加载View

(1).CustomView *myView = [[NSBundle mainBundle] loadNibNamed:@"CustomView" owner:nil options:nil].lastObject;

不会调用init,和initwithframe方法

(2).CustomView *myView = [[CustomView alloc] init];

先调用init方法->再调用initwithframe方法

(3).如果在xib中嵌入了CustomView视图，会调用initwithcoder->再调用awakefromnib方法