如何针对给定的班级大小检测UIView是否存在？

I want to build an app that works similar to SplitViewController but without using SplitViewController. When the app runs in iPad, two view much show up simultaneously. Master and Detail. When the app runs in an iPhone, only Master view will show up and when a user taps on an item the detail view will show up. I want to build an app that works similar to Sp