The Ruby Variable, Class, And Constant Name Guide

As I’m learning Ruby, I’m having a somewhat hard time remembering all the specific Ruby syntax. So this is more of a guide to myself (by writing it out, I’m hoping I’ll remember it better), and you’re welcome to follow along…

Local Variables


  • name
  • student_id
  • graduation2012
  • _photo

A local variable is a variable that is given local scope and is accessible from a declared method or block in which it is declared. In Ruby, local variables start with a lower-case letter or an underscore, and can have numbers in the name. camelCase is not really used for local variables in Ruby, so use the underscores instead.

Instance Variables


  • @name
  • @student_id
  • @graduation2012
  • @_photo

An instance variable is a variable defined in a class, for which each object of the class has a separate copy. Instance variables in Ruby are declared with an “@” sign in front of the variable name.

Class Variables


  • @@name
  • @@student_id
  • @@YEAR

An class variable is a variable defined in a class, for each each object of the class has a single copy. If you’d like to learn more about the difference between class and instance variables, here is a great explanation. Class variables start with “@@” signs in from of the variable name.

Global Variables


  • $name
  • $_photo
  • $Year

A global variable is accessible in every scope. In Ruby, the global variables start with a “$” sign in front of the variable name.

Class Names


  • MyClass
  • School
  • Student

In Ruby, class names start with a capital letter and could be CamelCase.

Constant Names


  • PI

Constants in Ruby are all caps.

Wow, writing these out really did help me remember all of these 🙂

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