Ruby - Wyatt's Notes

import Citations from ‘@components/Citations.astro’

Welcome to the Ruby notes. Ruby is a dynamic, interpreted language designed for programmer happiness, with a clean syntax, powerful metaprogramming capabilities, and an emphasis on convention over configuration.

Ruby’s elegant syntax and powerful metaprogramming features make it ideal for rapid development. Understanding Ruby’s object model (everything is an object, including numbers and booleans), its block and iterator patterns, and its metaprogramming capabilities (method_missing, eigenclasses, refinements) gives you insight into dynamic language design that transfers to Python, JavaScript, and other languages.

• Object model: Everything is an object, classes, methods, and blocks are all first-class citizens
• Blocks, Procs, and Lambdas: Three levels of closures with different behaviours for argument handling
• Metaprogramming: Define methods at runtime, open classes, and use method_missing to handle dynamic calls
• Mixins: Code reuse through modules, avoiding the diamond inheritance problem
• Testing and conventions: RSpec, Minitest, and Ruby community conventions

Install Ruby via rbenv (https://github.com/rbenv/rbenv) or your system package manager. Open IRB (Interactive Ruby) and experiment with the basics: 5.times { puts "Hello" }, [1,2,3].map { |n| n * 2 }and defining classes with attr_accessor. The “Ruby in 20 Minutes” tutorial (ruby-lang.org) is an excellent starting point. Build a small project, a command-line tool or a simple web app with Sinatra, to apply what you learn.

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Ruby prioritises developer happiness: Designed by Yukihiro Matsumoto, Ruby emphasises natural, readable syntax and elegant solutions. Its “everything is an object” philosophy and powerful blocks make Ruby expressive and fun to write.

Why it matters: Ruby powers Rails, one of the most productive web frameworks. Ruby’s emphasis on convention over configuration enabled rapid web application development.

The key insight: Ruby’s blocks and iterators provide a clean alternative to loops, iterating over collections with .each, .map, and .select is more readable than traditional for loops.

Start with the basics: variables, methods, blocks, and classes. Then move to metaprogramming (method_missing, eigenclasses, refinements) and Rails integration. Ruby’s object model is consistent, everything is an object, including numbers, strings, and nil. Understanding this uniformity is key to writing idiomatic Ruby.

## Variables and types
name = "Ruby"          # String
version = 3.3          # Float
count = 42             # Integer
flag = true            # Boolean
nothing = nil          # Nil

# Collections
array = [1, 2, 3, 4, 5]
hash = { name: "Ruby", type: "language" }

# Blocks and iterators
array.each { |n| puts n }
array.map { |n| n * 2 }
array.select { |n| n > 3 }
array.reduce(0) { |sum, n| sum + n }

# Classes
class Greeter
  attr_accessor :name
  def initialize(name)
    @name = name
  end
  def greet
    "Hello, #{name}!"
  end
end

Confusing nil with empty string/array: nil is the absence of a value. "" is an empty string. [] is an empty array. Using .nil? vs .empty? vs checking size gives different results. nil.to_s returns "", which can mask nil values.

Using == for string comparison: In Ruby, == compares string content (unlike Java). But equal? compares object identity. eql? compares content and type. Use == for most string comparisons, but be aware of the distinction.

Forgetting Ruby is object-oriented: Everything in Ruby is an object, including integers, strings, and nil. 5.times { … } works because integers are objects. This means methods can be called on any value, which is different from languages with primitive types.

<Citations sources={[ {title=“Programming Ruby”, author=“Thomas, Fowler and Hunt”, year=“2020”, type=“book”}, {title=“The Well-Grounded Rubyist”, author=“Black”, year=“2018”, type=“book”}, ]} />

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