三三理论

Visitor mode is to encapsulate some operations applied to a certain data structure. Once these operations need to be modified, the data structure that accepts this operation can be saved unchanged. Visitor mode is suitable for systems with relatively stable data structures. It reduces the coupling degree between data structures and operations acting on data structures, making the set of operations relatively free to change. The specific structure diagram is as follows:扎营之后没多久，飞影就送来了消息，他们的效率很高，不等汉王催促便早已准备妥当。这会子平武受了刺jī，又一心想着报仇雪恨，可以说是求胜心切。Later, she changed her mind, saying that she had two miscarriages in 2003 and 2008. She pretended to be pregnant and used her colleague's baby ultrasound images to deceive her husband. 　　Brother, what should I do with this? Now position 6 is a critical strike, and there is no tiger with the main attribute critical strike or explosive injury.　　雨玲下船去送妈妈最后一程，却被巡捕发现，带她上船辨认豪杰。豪杰装扮成船工，雨玲没有指出豪杰5. Be careful not to confuse the two function lists of "save for later" and "add items to wish list". Usually, the products of the saved shopping cart include the products that the shopper intends to purchase, while the wish list does not necessarily include the products that the customer intends to purchase, which may be the gifts that the shopper wishes to receive or may give.