Refactoring: Improving the Design of Existing Code (Addison-Wesley Signature Series (Fowler))

by Martin Fowler

The heart of a good software design is its modularity—which is my ability to make most modifications to a program while only having to understand a small part of it. To get this modularity, I need to ensure that related software elements are grouped together and the links between them are easy to find and understand. But my understanding of how to do this isn’t static—as I better understand what I’m doing, I learn how to best group together software elements. To reflect that growing understanding, I need to move elements around. All functions live in some context; it may be global, but usually it’s some form of a module. In an object-oriented program, the core modular context is a class. Nesting a function within another creates another common context. Different languages provide varied forms of modularity, each creating a context for a function to live in.