@property (nonatomic, strong) LHCustomModalTransition *transition;

......

//---初始化要弹出跳转的视图控制器
ModalViewController *modalVC = [ModalViewController new];
//---必须添加这句.自定义转场动画
modalVC.modalPresentationStyle = UIModalPresentationCustom;

//---必须强引用，否则会被释放，自定义dismiss的转场无效
self.transition = [[LHCustomModalTransition alloc]initWithModalViewController:modalVC];

//-----------------可选的以下设置

self.transition.dragable = YES;//---是否可下拉收起
self.transition.transitionStyle = LHCustomScaleTransitionStyle;//---设置缩放样式
self.transition.behindViewAlpha = 0.5f;//---设置缩放比例
self.transition.duration = 2.0f;//---设置缩放时间
self.transition.behindViewAlpha = 0.5f;//---设置要隐藏的VC透明度

//--------------------------------
 
//---设置代理为自定义的转场
modalVC.transitioningDelegate = self.transition;