From design patterns to reactive programming

Even though the design pattern movement is aligned with OOP, and reactive programming is aligned towards FP, there are close similarities between them. In a previous chapter, we learned the following:

• The OOP model is good for modeling the structural aspects of a system.
• The FP model is good for modeling the behavioral aspects of a system.

To illustrate the connection between OOP and reactive programming, we will write a program that will traverse directories to enumerate files and sub-folders within a given folder.

We will create a composite structure that contains the following:

• A FileNode (inherits from EntryNode) that models file information
• A DirectoryNode (inherits from EntryNode) that models folder information

After defining the preceding composites, we will define visitors for the following:

• Printing filenames and folder names
• Converting a composite hierarchy to a list of filenames

Without further ado, let's get into the meat of the stuff. Take...