php – Doctrine 2让我质疑集合的目标,我可以在集合中使用哪种方

Collections are collections,they hold elements and provide means to
iterate over them or do other typical collection stuff (count,filter
items,add items,remove items,…),always not caring about the
exact nature of the items (products,articles or whatever).
getTotalPrice or getTotalWeight on a collection are completely
misplaced and extending collection classes a similar bad idea in most
situations. It goes against many guidelines,single responsibility
principle being one of them. Put your business logic on your domain
objects/classes themselves,not on the collections. Collections are
just generic data containers.

我的问题是,如果我想对一组书籍对象做一些事情,比如将它们分类并计算每个类别中的数量,那么在集合类中创建一个方法来执行此操作是不正确的吗？或者我应该在实体中创建静态函数来对集合进行排序？我只是不确定我会把这种功能放在哪里….提前感谢您抽出时间阅读这篇文章.干杯!