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Ruby Style Guide

Based on Chris Neukirchen's Ruby Style Guide.


  • Use UTF-8

  • Use 2 space indent, no tabs.

  • Use Unix-style line endings.

  • Use spaces around operators, after commas, colons and semicolons, around { and before }.

  • No spaces after (, [ and before ], ).

  • Use one space before statement modifiers (postfix if, unless, while and until).

  • Indent when as deep as case.

  • Use an empty line before the return value of a method (unless it only has one line), and an empty line between defs.

  • Use empty lines to break up a long method into logical paragraphs.

  • Keep lines fewer than 80 characters.

  • Avoid trailing whitespace.

  • Don't align variables/constants assignments or hash keys/values vertically.


  • Use def with parentheses when there are arguments.

  • Use parentheses for method calls when there are arguments, unless it's part of a DSL.

  • Use && and || for boolean expressions.

  • Use {...} for single-line blocks and do...end for multi-line blocks.

  • Avoid return where not required.

  • Avoid using return inside blocks.

  • Avoid line continuation (\) where not required.

  • Avoid using the return value of = in comparisons.

  • Use ||= freely.

  • Avoid the and and or operators.


  • Use snake_case for methods.

  • Use CamelCase for classes and modules. (Keep acronyms like HTTP, RFC, XML uppercase.)

  • Use SCREAMING_SNAKE_CASE for other constants.

  • Use _ or names prefixed with _ for unused or private variables.

  • When defining binary operators, name the argument "other".


  • Comments longer than a word are capitalized and use punctuation.

  • Avoid superfluous comments.

The rest:

  • Avoid writing methods that span more than 10 lines.

  • Avoid writing methods that receive more than 3 parameters.

  • Use def self.method to define singleton methods.

  • Avoid needless metaprogramming.

  • Don't use rescue as a predicate.

  • Don't use catch-all rescue.

  • Don't use case without an else branch.

  • Use the hashrocket notation (=>) to build a literal Hash.

  • Use doublequotes for one-line strings.


  • Code in a functional way, avoid mutation when it makes sense.

  • Do not mutate arguments unless that is the purpose of the method.

  • Do not mess around in core classes when writing libraries.

  • Do not program defensively.

  • Keep the code simple.

  • Don't overdesign.

  • Don't underdesign.

  • Avoid bugs.

  • Read other style guides and apply the parts that don't dissent with this list.

  • Be consistent.

  • Use common sense.


Ruby Style Guide



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