如何让推送通知打开某个视图控制器?

I looked on SO but I wasn't able to find any question that discusses when you receive a push notification how can you then open a specific view controller. For example if you are creating an app like WhatsApp and you receive two different push notifications ie messages from two different users how would you direct from the app delegate to the respective viewController?I looked on SO but I wasn't able to find any qu