Pebellslearn by building
0%
RoadmapsMatrixCoursesSandboxSign in
Ruby Basics  ›  Capstone Project

Naming Conventions

Naming conventions 15 minRuby uses snake_case for variables and methods, CamelCase for classes and modules, SCREAMING_SNAKE_CASE for constant values, a trailing ? for yes/no methods and a trailing ! for the more dangerous twin of a method.

Naming Conventions

Ruby programmers can often guess what a name is before reading its definition. open? answers yes or no. sort! changes something in place. OrderQueue is a class. This is not luck; it is a set of shared habits, and following them makes your Bean Cart code read like everyone else's Ruby.

The rule

snake_case for things, CamelCase for kinds, a final ? or ! for warnings.

The core rules:

What Style Bean Cart example
Variables, methods snake_case cups_sold, daily_total
Classes, modules CamelCase CoffeeCart, OrderQueue
Constant values SCREAMING_SNAKE_CASE TAX_RATE, MAX_CUPS
File names snake_case.rb coffee_cart.rb holds CoffeeCart

Two punctuation marks are allowed at the end of a method name, and they carry meaning:

  • A trailing ? marks a predicate: a method that answers a yes/no question and returns true or false. Ruby's own examples: empty?, nil?, even?, include?.
  • A trailing ! marks the "dangerous" version of a method that also exists without it. Usually the ! version changes the object itself, while the plain one returns a new object:
name = "bean cart"
name.upcase    # => "BEAN CART", name is unchanged
name.upcase!   # name itself is now "BEAN CART"
[3, 1, 2].empty?   # => false

The ! does not simply mean "changes things". Plenty of methods change their object without one, such as push or delete. It means "careful: there is a safer twin".

Other habits worth copying:

  • Name a method that sets a value with a trailing =: price= lets you write cart.price = 5.
  • Avoid get_ and is_ prefixes: prefer price over get_price, and open? over is_open.
  • A leading underscore, as in _unused, tells readers (and Ruby's warnings) that a variable is deliberately ignored.

The shortcut

Read a name's shape: its first letter and its last character. Capital first letter means a class, module or constant. Ends in ?: expect true or false. Ends in !: expect a safer twin without the !, and possibly changed data.

Naming parts of Bean CartStep 1 of 4

  1. A blueprint for carts

    It is a kind of thing, so it takes CamelCase: CoffeeCart, stored in coffee_cart.rb.

Drills

Answer fast — trust the rule.

quick drill

Which is the conventional name for a class?

quick drill

What should a method named sold_out? return?

quick drill

After name = "tea" and name.capitalize, what is name?

quick drill

Which name follows Ruby conventions best?

quick drill

What does a trailing ! on a method name tell you?

Remember

  • snake_case for things, CamelCase for kinds, SCREAMING_SNAKE_CASE for fixed values.
  • Read the shape: ? means a yes/no answer; ! means a more dangerous twin exists.
  • Trap: thinking ! simply means "mutates", or writing get_ and is_ prefixes.

Practice — level up

0/1 solved

Write your answer, then compare it with a rubric and a model answer.

ExplainName the Bean Cart parts

Name these parts of Bean Cart following Ruby conventions and explain each choice: a class for the cart, a method that says whether the cart is open, today's total, the maximum number of cups, and a method that changes the menu in place when a safer copying version also exists.