This chapter discusses the don’t repeat yourself (DRY) principle. It is another important principle that a professional coder follows when writing a piece of code in an application. The SRP and OCP principles that you learned about in Chapter 4 are also related to the DRY principle. Andy Hunt and Dave Thomas first wrote about this principle in their book The Pragmatic Programmer. The DRY principle is stated as follows:
Every piece of knowledge must have a single, unambiguous, authoritative representation ...
