Ruby 3.0 Release: New Features, RBS Type System, Ractor Concurrency, and Scheduler Enhancements

Ruby 3.0 was released on Christmas as announced by its creator Yukihiro Matsumoto, promising a three‑fold speed increase over Ruby 2.

The release focuses on performance (MJIT), concurrency (Ractor and Fiber Scheduler), and static type analysis (RBS and TypeProf).

RBS is a language for describing Ruby program types; the rbs gem ships with Ruby 3.0 and enables tools to understand type definitions, supporting advanced features such as union types, method overloads, generics, and duck‑typing interfaces.

Example RBS definition:

module ChatApp
  VERSION: String

  class Channel
    attr_reader name: String
    attr_reader messages: Array[Message]
    attr_reader users: Array[User | Bot]  # `|` means union types, `User` or `Bot`.

    def initialize: (String) -> void

    def post: (String, from: User | Bot) -> Message   # Method overloading is supported.
                | (File, from: User | Bot) -> Message
  end
end

Ractor (experimental) implements an Actor‑style concurrency model that allows parallel execution without shared‑state concerns; a sample program shows two Ractors computing prime? in parallel, roughly doubling speed.

require 'prime'

# n.prime? with sent integers in r1, r2 run in parallel
r1, r2 = *(1..2).map do
  Ractor.new do
    n = Ractor.recv
    n.prime?
  end
end

# send parameters
r1.send 2**61 - 1
r2.send 2**61 + 15

# wait for the results of expr1, expr2
p r1.take #=> true
p r2.take #=> true

The new Thread#scheduler intercepts blocking operations, enabling lightweight concurrency without modifying existing code. Supported classes/methods include Mutex#lock , Mutex#unlock , ConditionVariable#wait , Queue#pop , Thread#join , Kernel#sleep , IO#wait , IO#read , IO#write , among others, while IO#select remains unsupported.

Ruby 3 also redesigns single‑line pattern matching, adding the => operator and the in keyword for boolean pattern checks, with examples demonstrating the new syntax.