Ruby/Rails Style Guide

Whitespace

Use 2-space indentation (no tabs).
Remove trailing whitespace.
Use Unix-style line endings.
Use spaces around operators, after commas, colons and semicolons, around { and before }.
Use two spaces before statement modifiers (e.g. postfix if, unless, while, until, or rescue).
Use empty lines to break up a long method into logical paragraphs.
Keep lines to fewer than 132 characters.
Do not indent temporary or debugging code (e.g. debugger), but keep flush with left column for visibility.
Do not indent class access control statements (e.g. protected). That is, they should be aligned with the opening class and closing end lines.

Method names should start with a lower case letter, and should be in all lower-case: method_name
Prefer attr_reader, attr_writer, attr_accessor for simple attributes.
Accessor and mutator methods are simply the name of the attribute (without get_ or set_ prefix).
Prefer attribute= over set_attribute.
Methods that return a boolean should end in ? and do not have the is_ prefix: prefer active? over is_active or is_active.
Method names should end in ! if the method:
- Changes the object directly, as opposed to returning a modified copy of the object.
- Throws an exception on a failure condition, as opposed to returning nil or false.

Always use parentheses around arguments in a function definition.
Use && and || for boolean expressions, and and or for control flow.
Avoid multiline ternary operator ( ?: ), prefer if.
Prefer methods over comparisons, e.g.:
Prefer unless over if !, except when there are elsif or else clauses.
- t.empty? instead of t.size == 0
- t.zero? instead of t == 0