Learn Ruby

Run Ruby scripts and IRB, print with puts and p, and meet Ruby's everything-is-an-object idea.

Assign variables and work with Integer, Float, String, Symbol, true, false and nil, including Ruby's truthiness rule.

Branch with if, unless and case/when, use modifier forms, and loop with while, until and times.

Interpolate and manipulate strings, understand mutability and frozen literals, and know when to use symbols.

Define methods with positional, optional, keyword and splat arguments, and rely on implicit returns.

Create and access arrays, hashes and ranges, including default values and symbol-key shorthand.

Pass blocks to each, map and select, and write your own iterators with yield.

Use Enumerable's power tools: reduce, group_by, partition, tally, each_with_object, sort_by and friends.

Turn blocks into objects with Proc and lambda, understand their differences, and pass methods around.

Build custom Enumerators, iterate externally with next, and process infinite or huge sequences lazily.

Define classes with initialize, instance variables and attr_accessor, and customise to_s and comparison.

Use modules as namespaces and mixins with include, extend and prepend, and implement Comparable and Enumerable.

Raise and rescue exceptions, use ensure and retry, and design a custom error hierarchy.

Destructure arrays and hashes with case/in, guards, pins and find patterns, and use => and in as one-liners.

Install libraries as gems, declare dependencies in a Gemfile, lock them with Bundler and run with bundle exec.

Read and write files safely with blocks, work with paths, and parse JSON and CSV from the standard library.

Write tests with Minitest's assertions and RSpec's describe/it/expect style, and stub collaborators.

Understand singleton classes, method lookup through ancestors, self, and how class methods really work.

Generate methods with define_method, call them dynamically with send, and handle unknown calls with method_missing.

Combine blocks, instance_eval and method chaining to build readable internal DSLs like Rails routes and RSpec.

Use threads, Mutex and Queue for I/O concurrency, understand the GVL, and know what Ractors offer for parallelism.

Use Fibers as lightweight coroutines and understand how the fiber scheduler enables non-blocking I/O.

Learn how CRuby allocates objects, how its generational GC works, and how to find allocation hot spots and leaks.

Enable YJIT, benchmark correctly, profile with stackprof or vernier, and write code the JIT can optimise.