无意中发现，有人创建UIButton这样写

UIButton *previousButton = [UIButtonbuttonWithType:101];

一看原来是私有api

UIButton *previousButton = [UIButton buttonWithType:101];    [previousButton setTitle:@"<" forState:UIControlStateNormal];    previousButton.frame = CGRectMake(0.f, 0.f, 30.f, 80.f);    previousButton.center = CGPointMake(previousButton.frame.size.width / 2.f, pagingView.center.y);    [previousButton addTarget:pagingView action:@selector(scrollToPreviousPage) forControlEvents:UIControlEventTouchUpInside];    [self.view addSubview:previousButton];

　　

 

更多UIButton 私有api