我有模型对象:classAnimal{//...}和子类:classDog:Animal{//...}classCat:Animal{//...}我还创建了泛型类classAnimalController{varanimal:T?funcfeed(animal:T){letfood=Food(T.self)animal.feed(food)}}问题来了:classMainViewController:UIViewController{varcontroller:AnimalController?//MARK:-LifecycleoverridefuncviewDidLoad(){sup