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Visitor pattern decouples the data structure from the operations acting on the structure, making the operation set relatively free to evolve. Visitor pattern is suitable for systems with relatively stable data structure and easy change of algorithm. Because visitor mode makes it easy to increase algorithm operation. If system data structure objects are easy to change and new data objects are often added, visitor mode is not suitable. The advantage of visitor mode is that it is easy to add operations, because adding operations means adding new visitors. Visitor mode centralizes the relevant behaviors into one visitor object, and its changes do not affect the system data structure. Its disadvantage is that it is difficult to add new data structures. -From EncyclopediaTwo implementations:Generally speaking, a delegate is a class that maintains a field inside and points to a method. Events can be regarded as variables of one delegate type, and multiple delegates or methods are cancelled through event registration. This article uses delegate and event execution methods to understand the difference between the two.一家跨国制药公司“葛安公司”，与国内某沿海城市合作兴建了一座大型生物工程基地。西海医院院长徐谦，感觉到葛安在医院下属的肝病医疗中心干着某种非法药物实验的勾当，但对方组织极其严密，违法活动不着痕迹。徐谦又发现葛安的人还意图窃取自己的导师、在世界流行病领域享有盛誉的肝病中心主任凌知渊正在秘密研究的某项重大科研成果(“黑郁金香”病毒研究)。　　郑在咏将出演在国立科学搜查研究院工作了10年的法医白范。他虽然是公认的实力派,但却是性格冷漠并执着于看不见的真相的天才和怪人。Https://www.jiemian.com/article/2011028.htmlPrivileges.py