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This article mainly introduces "what is the motivation of the web visitor pattern". In the daily operation, I believe that many people have doubts about the motivation of the web visitor pattern. The editor has consulted all kinds of materials and sorted out simple and easy-to-use operation methods. I hope it will be helpful to answer the doubts about "what is the motivation of the web visitor pattern?" Next, please follow the editor to study!

Intention

Assembles operations that act on individual elements in a data structure into a single action class. In this way, when you need to extend the operation on the elements in the data structure, you only need to extend the operation class instead of modifying the operation object class itself in the data structure.

motivation

Consider a tree data structure formed using a combined pattern. One of the benefits of using a composite pattern is that you can increase operations on each element of the entire data structure in a transparent manner. The implementation is very simple by preparing the same method in the composite class Composite and calling the corresponding method for each child element in this method.

Def reset_connections (self, memo): Component.reset_connections (self, memo) for child in self.iter (): child.reset_connections (memo)

This approach really works well, at least when it was first used to add functionality, the designer must have thought so. However, with the increase in the number of uses, designers will sooner or later find that every time it is the same structure, changing the content of the operation slightly becomes another function.

On the plus side, this repeatability can be said to solve different problems in the same way, reducing the difficulty of adding new features, which is certainly not wrong. But from another point of view, after all, the existing code is modified when the function is added. Is it possible to add new features without modifying existing code?

The same structure is the breakthrough of this problem, and the visitor pattern is the solution to this problem.

At this point, the study of "what is the motivation of the web Visitor pattern" is over. I hope to be able to solve your doubts. The collocation of theory and practice can better help you learn, go and try it! If you want to continue to learn more related knowledge, please continue to follow the website, the editor will continue to work hard to bring you more practical articles!

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