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Ruby Flashcards (Basics)

Ruby Basics — Flashcards

30 flashcards covering core Ruby concepts. Tap a card to reveal the answer.

Additional Flashcard Topics

  • Everything is an Object: integers, booleans, nil, and even classes are objects. Methods like 5.times { puts "hi" } work because integers are objects with methods.

  • Blocks, Procs, Lambdas: blocks { } are closures passed to methods. Procs are anonymous functions; lambdas enforce arity. yield calls the block passed to a method.

  • Metaprogramming: method_missing, define_method, class_eval. Ruby can modify classes and create methods at runtime — powerful but can be confusing.

  • Modules and Mixins: modules group methods that can be mixed into classes. include adds instance methods; extend adds class methods. No multiple inheritance.

  • Enumerable Module: each, map, select, reduce — any class that defines each can use all Enumerable methods. This is Ruby’s most powerful abstraction.

Intuition

Ruby is a language optimised for developer happiness — everything is an object (including integers and booleans), and blocks/procs/lambdas make functional patterns feel natural. Metaprogramming is Ruby’s superpower: you can define methods at runtime, open classes and add methods (monkey patching), and use method_missing to handle calls to undefined methods. Mixins via modules provide code reuse without the diamond inheritance problem. Ruby’s syntax is designed to read like English, prioritising expressiveness over ceremony.

Common Pitfalls

  • Monkey patching risks: Reopening a class and changing method behaviour affects every instance globally — this is powerful but can introduce hard-to-debug conflicts between libraries.
  • Symbol vs string: :symbol and "string" are different — symbols are immutable and interned (memory efficient), strings are mutable and duplicated. Use symbols for hash keys and identifiers.
  • Block vs proc vs lambda: Blocks are not objects (can’t be stored in variables), Procs don’t check argument count, and Lambdas do — mixing them up causes subtle argument-passing bugs.
  • Frozen string literals: In Ruby 2.3+, # frozen_string_literal: true makes string literals immutable. Forgetting this pragma can cause unexpected mutations.
  • self in blocks vs methods: self in a block refers to the enclosing context; self in a method refers to the receiver. This distinction matters for metaprogramming.

Cross-References

  • Ruby Practice: Auto-graded problems testing the same core Ruby concepts covered in these flashcards.
  • Elixir Basics: Functional programming and pattern matching concepts that Ruby also supports.
  • Python Basics: Dynamic typing and object-oriented patterns compared across languages.