命令模式与访客模式 [英] Command Pattern vs. Visitor Pattern

问题描述

允许访问者修改接收者的状态通常是可以接受的，还是应该改为使用命令模式?

Is it generally acceptable to allow a Visitor to modify state of the Receiver, or should that be a Command pattern instead?

推荐答案

访问者模式的目的是允许将新操作添加到类继承结构中，而无需对该继承结构进行任何修改.我从未见过有人建议仅接受只读操作.唯一的限制是，添加的操作只能使用类继承关系的公共接口.

The purpose of the visitor pattern is to allow new operations to be added to a class heirarchy without modification to that heirarchy. I've never seen anyone suggesting that only read-only operations are acceptable. The only limitation is that the added operations should only use the public interface of the class heirarchy.

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