1.打印viewcontroller
po [[UIApplication sharedApplication].keyWindow.rootViewController _printHierarchy]
打印结果
2.打印UIView对象
po [[UIApplication sharedApplication].keyWindow recursiveDescription]
po [self.view recursiveDescription]
打印结果
3.简化的recursiveDescription
po [[UIApplication sharedApplication].keyWindow _autolayoutTrace]
4.打印某个对象所有instance的名字和值
po [self.view _ivarDescription]
5.打印对象的类方法、实例方法、属性
po [self.view _methodDescription]