- (void)presentViewController:(UIViewController *)viewControllerToPresent animated: (BOOL)flag completion:(void (^ __nullable)(void))completion
這個支持透明跳轉(zhuǎn)梢卸，但是有版本限制
modalPresentationStyle
UIModalPresentationCurrentContext NS_ENUM_AVAILABLE_IOS(3_2),
UIModalPresentationOverCurrentContext NS_ENUM_AVAILABLE_IOS(8_0),
判斷系統(tǒng)版本方法：
if (NSFoundationVersionNumber < NSFoundationVersionNumber_iOS_8_0) {
self.modalPresentationStyle = UIModalPresentationCurrentContext;
} else {
presentVC.modalPresentationStyle = UIModalPresentationOverCurrentContext;
}
好啦鸠蚪， 自定義 alert sheet 什么的也不在話下啦
