ruby-expert

Ruby Expert

Expert guidance for Ruby development, including Ruby 3+ features, Rails framework, testing with RSpec, and Ruby best practices.

Core Concepts

Ruby 3+ Features

• Pattern matching
• Ractors (parallel execution)
• Fibers (cooperative concurrency)
• Type signatures (RBS)
• Endless methods
• Numbered block parameters
• Hash literal value omission

Object-Oriented

• Everything is an object
• Classes and modules
• Inheritance and mixins
• Method visibility (public, private, protected)
• Singleton methods and eigenclasses
• Duck typing

Functional Features

• Blocks, procs, and lambdas
• Higher-order functions (map, reduce, select)
• Enumerables
• Lazy evaluation

Modern Ruby Syntax

Pattern Matching (Ruby 3.0+)

# Case/in pattern matching
def process_response(response)
  case response
  in { status: 200, body: }
    puts "Success: #{body}"
  in { status: 404 }
    puts "Not found"
  in { status: 500..599, error: message }
    puts "Server error: #{message}"
  else
    puts "Unknown response"
  end
end

# Rightward assignment
response = { status: 200, body: "OK" }
response => { status:, body: }
puts status  # 200
puts body    # "OK"

# Array pattern matching
def summarize(data)
  case data
  in []
    "Empty"
  in [item]
    "Single item: #{item}"
  in [first, *rest]
    "First: #{first}, Rest: #{rest.length} items"
  end
end

Endless Methods

# Single-line method definition
def greet(name) = "Hello, #{name}!"

def square(x) = x * x

def full_name = "#{first_name} #{last_name}"

class User
  attr_reader :name, :email

  def initialize(name:, email:) = (@name = name; @email = email)

  def admin? = @role == :admin
end

Numbered Block Parameters

# Use _1, _2, etc. for block parameters
[1, 2, 3].map { _1 * 2 }  # [2, 4, 6]

{ a: 1, b: 2 }.map { "#{_1}: #{_2}" }  # ["a: 1", "b: 2"]

users.sort_by { [_1.last_name, _1.first_name] }

Hash Literal Value Omission

name = "Alice"
age = 30
email = "[email protected]"

# Before
user = { name: name, age: age, email: email }

# After (Ruby 3.1+)
user = { name:, age:, email: }