Before we jump into more code, let's think for a moment about something you encounter pretty much every day when you read a news article or email: the way we organize words to express and clarify meaning. For example, a paragraph is a collection of sentences, aligned by a topic sentence and bundled up or closed by a closing sentence. A paragraph can persuade or offend, direct, or explain. A paragraph has a function.
"Code paragraphs" are called, depending on language, "functions," "procedures,"
"methods," or "subroutines." They bundle up expressions and statements to
accomplish a task. Just as "Make a Sandwich" encompasses specific, "atomic"
actions like like "get slice of bread," "get jelly," etc.,
retrieve_avatar_image_for_user encompasses logic like if user_name == nil
or if image_url == nil.
To have code that is easy to read, debug, and maintain, we need to bundle collections of atomic activities into "code paragraphs" that do work. Ruby calls these "methods."
This process of bundling up small atoms into a method is called "abstraction." "Abstraction" comes from the Latin word for "to pull away." When we're further away, many details are hard to see. Only the most relevant shapes are recognizable. For example, when you're on an airplane and are over a city the details of the mileage, what's in the cup holder, the make, or the model of the cars below are invisible, they're not essential. What is is the color of the little dots moving up and down the freeway. By abstracting we see what's more true generally.
Here's a few more "abstractions:"
Abstraction is a natural part of learning to converse. When you're first learning to communicate, you don't know enough to start talking about abstractions. You prefer to think about real, visible, tangible things. But as you learn about opposites, how things are similar (and how perhaps one thing is dissimilar) you grow in your ability to abstract.
In fact, the thing that makes most higher learning "higher" is that the discussion, work, and discovery is focused on uncovering general principles that allow us to predict how things will work more-or-less most of the time. Amazingly, this was considered a pretty revolutionary idea at the time when Galileo and Newton started doing it. The moment that natural philosophers started looking for these "general rules of how things work," science as we know it was born.
Ruby calls bundles of statements that, together, accomplish a unit of work or process, methods. In Programming as Conversation 3 we'll learn to take our expressions and statements and bundle them up into abstractions called methods.