Book Image

Polished Ruby Programming

By : Jeremy Evans
Book Image

Polished Ruby Programming

By: Jeremy Evans

Overview of this book

Anyone striving to become an expert Ruby programmer needs to be able to write maintainable applications. Polished Ruby Programming will help you get better at designing scalable and robust Ruby programs, so that no matter how big the codebase grows, maintaining it will be a breeze. This book takes you on a journey through implementation approaches for many common programming situations, the trade-offs inherent in each approach, and why you may choose to use different approaches in different situations. You'll start by refreshing Ruby fundamentals, such as correctly using core classes, class and method design, variable usage, error handling, and code formatting. Then you'll move on to higher-level programming principles, such as library design, use of metaprogramming and domain-specific languages, and refactoring. Finally, you'll learn principles specific to web application development, such as how to choose a database and web framework, and how to use advanced security features. By the end of this Ruby programming book, you’ll be a well rounded web developer with a deep understanding of Ruby. While most code examples and principles discussed in the book apply to all Ruby versions, some examples and principles are specific to Ruby 3.0, the latest release at the time of publication.
Table of Contents (23 chapters)
Section 1: Fundamental Ruby Programming Principles
Section 2: Ruby Library Programming Principles
Section 3: Ruby Web Programming Principles

Understanding how constants are just a type of variable

Ruby has constants, but unlike constants in most other languages, Ruby's constants are actually variables. It's not even an error in Ruby to reassign a constant; it only generates a warning. Say you try the following code:

A = 1
A = 2

Then you'll see it only generates two warnings:

# warning: already initialized constant A
# warning: previous definition of A was here

At best, Ruby's constants should be considered only as a recommendation. That being said, not modifying a constant is a good recommendation. In general, you shouldn't modify constants unless you have to, especially constants that are in external code such as libraries.

You can think of a constant in Ruby as a variable type that can only be used by modules and classes, with different scope rules. As both modules and classes are objects, they can both have instance variables in addition to constants. When a class or module needs...