Visitor

This design pattern is usually a close friend of the Composite design pattern, which we discussed in Chapter 3, Understanding Structural Patterns. It can either extract data from a complex tree-like structure or add behavior to each node of the tree, much like the Decorator design pattern does for a single object.

My plan, being a lazy software architect, worked out quite well. My request-answering system from the chain of responsibility worked quite well and I don't have plenty of time for coffee. But I'm afraid some developers begin to suspect that I'm a bit of a fraud.

To confuse them, I plan to produce weekly emails with links to all the latest buzzword articles. Of course, I don't plan to read them myself – I just want to collect them from some popular technology sites.

Writing a crawler

Let's look at the following data structure, which is very similar to what we had when we discussed the Iterator design pattern:

Page(Container...