Transforming the Data

If you come from an object-oriented world, you’re used to programming with classes and their instances. When we code with objects, we’re thinking about the state. Much of our time is spent calling methods in objects and passing them to other objects. Based on these calls, objects update their own state and possibly the state of other objects. In this world, the class is king. It defines what each instance can do, and it implicitly controls the state of the data its instances hold. Our goal is data hiding.

But that’s not the real world. We want to get things done, not maintain the state. Let’s illustrate it through an example. Suppose ...