The Ruby Style Guide

Source Code Layout

Use two spaces per indentation level (aka soft tabs). No hard tabs. ^[link]

# standard
def some_method
  do_something
end

# non-standard - four spaces
def some_method
    do_something
end

Avoid ; to separate statements and expressions. Use one expression per line. ^[link]

# standard
puts 'foobar'

puts 'foo'
puts 'bar'

# non-standard
puts 'foobar';

puts 'foo'; puts 'bar'

Class definitions should be laid out in a standard fashion even if they have no body. ^[link]

# standard
class FooError < StandardError
end

# non-standard
class FooError < StandardError; end

# non-standard
FooError = Class.new(StandardError)

Avoid putting method definitions and the body on a single line. ^[link]

# standard
def some_method
  body
end

# non-standard
def too_much; something; something_else; end

# non-standard
def no_braces_method; body end

# non-standard
def no_braces_method; body; end

# non-standard
def some_method() body end

# non-standard
def no_op; end

Use spaces around operators, after commas, colons and semicolons, around { and before }. ^[link]

sum = 1 + 2
a, b = 1, 2
[1, 2, 3].each { |e| puts e }

The only exception, regarding operators, is the exponent operator:

# standard
e = M * c**2

# non-standard
e = M * c ** 2

Treat { and } consistently.

# standard
{ :one => 1, :two => 2 }

# non-standard
{:one => 1, :two => 2}

As far as embedded expressions go, omit spaces.

# standard - no spaces
"string#{expr}"

# non-standard
"string#{ expr }"

No spaces after (, [ or before ], ). ^[link]
```
some(arg).other
[1, 2, 3].size
```

No space after !. ^[link]

# standard
!something

# non-standard
! something

Use empty lines between method definitions and also to break up a method into logical paragraphs. ^[link]

def some_method
  data = initialize(options)

  data.manipulate!

  data.result
end

def some_method
  result
end

Indent when as deep as case. Space out the when clauses as separate paragraphs. ^[link]

# standard
case
when song.name == 'Misty'
  puts 'Not again!'

when song.duration > 120
  puts 'Too long!'

when Time.now.hour > 21
  puts "It's too late"

else
  song.play
end

# non-standard
case
  when song.name == 'Misty'
    puts 'Not again!'
  when song.duration > 120
    puts 'Too long!'
  when Time.now.hour > 21
    puts "It's too late"
  else
    song.play
end

When assigning the result of a conditional expression to a variable, use simple indentation. ^[link]

# standard
result = if some_cond
  calc_something
else
  calc_something_else
end

# standard
result =
  if some_cond
    calc_something
  else
    calc_something_else
  end

# non-standard
result = if some_cond
           calc_something
         else
           calc_something_else
         end

Avoid comma after the last parameter in a method call. ^[link]

# standard
some_method(size, count, color)

# non-standard
some_method(
             size,
             count,
             color,
           )

# non-standard
some_method(size, count, color, )

Do not use spaces around the = operator when assigning default values to method parameters: ^[link]

# standard
def some_method(arg1=:default, arg2=nil, arg3=[])
  # do something...
end

# non-standard
def some_method(arg1 = :default, arg2 = nil, arg3 = [])
  # do something...
end

Avoid line continuation \. ^[link]

# non-standard
result = 1 \
         - 2

long_string = 'First part of the long string' \
              ' and second part of the long string'

Avoid multi-line method chaining styles. ^[link]

# non-standard
one.two.three.
  four

one.two.three
  .four

Use simple indentation for the parameters of a method call if they span more than one line. ^[link]

# standard
def send_mail(source)
  Mailer.deliver(
    to: 'bob@example.com',
    from: 'us@example.com',
    subject: 'Important message',
    body: source.text
  )
end

# standard
def send_mail(source)
  Mailer.deliver(to: 'bob@example.com', from: 'us@example.com', subject: 'Important message', body: source.text)
end

# non-standard
def send_mail(source)
  Mailer.deliver(
      to: 'bob@example.com',
      from: 'us@example.com',
      subject: 'Important message',
      body: source.text)
end

# non-standard
def send_mail(source)
  Mailer.deliver(to: 'bob@example.com',
                 from: 'us@example.com',
                 subject: 'Important message',
                 body: source.text)
end

Align the elements of array literals spanning multiple lines. ^[link]

# standard
menu_item = [
  'Spam', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam',
  'Baked beans', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam'
]

menu_item =
[
  'Spam', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam',
  'Baked beans', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam'
]

# non-standard
menu_item =
  ['Spam', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam',
   'Baked beans', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam']

# non-standard
menu_item = ['Spam', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam',
  'Baked beans', 'Spam', 'Spam', 'Spam', 'Spam', 'Spam']

Add underscores to large numeric literals to improve their readability. ^[link]
```
# standard
num = 1_000_000

# non-standard
num = 1000000
```
Avoid trailing whitespace. ^[link]
End each file with a newline. ^[link]

Syntax

Use def with parentheses when there are arguments. Omit the parentheses when the method doesn't accept any arguments. ^[link]

# standard
def some_method
 # body omitted
end

# standard
def some_method_with_arguments(arg1, arg2)
 # body omitted
end

# non-standard
def some_method()
  # body omitted
end

 # non-standard
 def some_method_with_arguments arg1, arg2
   # body omitted
 end

Avoid using for. Use iterators. ^[link]

arr = [1, 2, 3]

# standard
arr.each { |elem| puts elem }

elem # => NameError: undefined local variable or method `elem'

# non-standard
for elem in arr do
  puts elem
end

elem # => 3

Never use then for multi-line if/unless. ^[link]

# standard
if some_condition
  # body omitted
end

# non-standard
if some_condition then
  # body omitted
end

Always put the condition on the same line as the if/unless in a multi-line conditional. ^[link]

# standard
if some_condition
  do_something
  do_something_else
end

# non-standard
if
  some_condition
  do_something
  do_something_else
end

Favor the ternary operator(?:) over if/then/else/end constructs. ^[link]

# standard
result = some_condition ? something : something_else

# non-standard
result = if some_condition then something else something_else end

Use one expression per branch in a ternary operator. This also means that ternary operators must not be nested. Prefer if/else constructs in these cases. ^[link]

# standard
if some_condition
  nested_condition ? nested_something : nested_something_else
else
  something_else
end

# non-standard
some_condition ? (nested_condition ? nested_something : nested_something_else) : something_else

Never use if x; .... Use the ternary operator instead. ^[link]

Use if and case as expressions which return a result. ^[link]

# standard
result =
  if condition
    x
  else
    y
  end

# non-standard
if condition
  result = x
else
  result = y
end

Use ! instead of not. ^[link]

# standard
x = !something

# non-standard
x = (not something)

Avoid multi-line ?: (the ternary operator); use if/unless instead. ^[link]

Favor modifier if/unless usage when you have a single-line body. Another good alternative is the usage of control flow and/or. ^[link]

# standard
do_something if some_condition

# standard
some_condition and do_something

# non-standard
if some_condition
  do_something
end

Favor unless over if for negative conditions (or control flow ||). ^[link]

# standard
do_something unless some_condition

# standard
some_condition or do_something

# non-standard
do_something if !some_condition

# non-standard
do_something if not some_condition

Avoid unless with else. Try rewriting these with the positive case first. ^[link]

# standard
if success?
  puts 'success'
else
  puts 'failure'
end

# non-standard
unless success?
  puts 'failure'
else
  puts 'success'
end

Don't use parentheses around the condition of an if/unless/while/until. ^[link]

# standard
if x > 10
  # body omitted
end

# non-standard
if (x > 10)
  # body omitted
end

Omit parentheses around parameters for methods that are part of an internal DSL (e.g. Rake, Rails, RSpec), methods that have "keyword" status in Ruby (e.g. attr_reader, puts) and attribute access methods. Use parentheses around the arguments of all other method invocations. ^[link]
```
class Person
  attr_reader :name, :age

  # omitted
end

temperance = Person.new('Temperance', 30)
temperance.name

puts temperance.age

x = Math.sin(y)
array.delete(e)

bowling.score.should == 0
```

Omit the outer braces around an implicit options hash. ^[link]

# standard
user.set(:name => 'John', :age => 45, :permissions => { :read => true })

# non-standard
user.set({ :name => 'John', :age => 45, :permissions => { :read => true }})

Omit both the outer braces and parentheses for methods that are part of an internal DSL. ^[link]

class Person < ActiveRecord::Base
  # standard
  validates :name, :presence => true, :length => { :within => 1..10 }

  # non-standard
  validates(:name, :presence => true, :length => { :within => 1..10 })
end

Omit parentheses for method calls with no arguments. ^[link]

# standard
Kernel.exit!
2.even?
fork
'test'.upcase

# non-standard
Kernel.exit!()
2.even?()
fork()
'test'.upcase()

Prefer {...} over do...end for single-line blocks. Avoid using {...} for multi-line blocks (multiline chaining is always ugly). Always use do...end for "control flow" and "method definitions" (e.g. in Rakefiles and certain DSLs). Avoid do...end when chaining. ^[link]

names = ['Bozhidar', 'Steve', 'Sarah']

# standard
names.each { |name| puts name }

# non-standard
names.each do |name|
  puts name
end

# standard
names.select { |name| name.start_with?('S') }.map { |name| name.upcase }

# non-standard
names.select do |name|
  name.start_with?('S')
end.map { |name| name.upcase }

Use the new lambda literal syntax for single line body blocks. Use the lambda method for multi-line blocks. ^[link]

# standard
l = ->(a, b) { a + b }
l.call(1, 2)

l = lambda do |a, b|
  tmp = a * 7
  tmp * b / 50
end

# non-standard
l = ->(a, b) do
  tmp = a * 7
  tmp * b / 50
end

# non-standard
l = lambda { |a, b| a + b }
l.call(1, 2)

Prefer proc over Proc.new. ^[link]

# standard
p = proc { |n| puts n }

# non-standard
p = Proc.new { |n| puts n }

Prefer proc.call() over proc[] or proc.() for both lambdas and procs. ^[link]

# standard
l = ->(v) { puts v }
l.call(1)

# non-standard
l = ->(v) { puts v }
l[1]

# non-standard
l = ->(v) { puts v }
l.(1)

Prefix with _ unused block parameters and local variables. ^[link]

# standard
result = hash.map { |_, v| v + 1 }

# standard
result = hash.map { |_k, v| v + 1 }

# non-standard
result = hash.map { |k, v| v + 1 }

Avoid return where not required for flow of control. ^[link]

# standard
def some_method(some_arr)
  some_arr.size
end

# non-standard
def some_method(some_arr)
  return some_arr.size
end

Avoid self where not required. ^[link]

# standard
def ready?
  if last_reviewed_at > last_updated_at
    worker.update(content, options)
    self.status = :in_progress
  end
  status == :verified
end

# non-standard
def ready?
  if self.last_reviewed_at > self.last_updated_at
    self.worker.update(self.content, self.options)
    self.status = :in_progress
  end
  self.status == :verified
end

Don't use the return value of = (an assignment) in conditional expressions unless the assignment is wrapped in parentheses. ^[link]

# standard
if (v = array.grep(/foo/))
  do_something(v)
  ...
end

# standard
v = array.grep(/foo/)
if v
  do_something(v)
  ...
end

# non-standard
if v = array.grep(/foo/)
  do_something(v)
  ...
end

Use shorthand self assignment operators whenever applicable. ^[link]

# standard
x += y
x *= y
x **= y
x /= y
x ||= y
x &&= y

# non-standard
x = x + y
x = x * y
x = x**y
x = x / y
x = x || y
x = x && y

Use ||= to initialize variables only if they're not already initialized. ^[link]

# standard
name ||= 'Bozhidar'

# non-standard
name = name ? name : 'Bozhidar'

# non-standard
name = 'Bozhidar' unless name

Use &&= to preprocess variables that may or may not exist. ^[link]

# standard
something &&= something.downcase

# standard
something = something && something.downcase

# standard
something = something.downcase if something

# non-standard
if something
  something = something.downcase
end

# non-standard
something = something ? nil : something.downcase

Avoid explicit use of the case equality operator ===. ^[link]

# standard
something.is_a?(Array)
(1..100).include?(7)
some_string =~ /something/

# non-standard
Array === something
(1..100) === 7
/something/ === some_string

Never put a space between a method name and the opening parenthesis. ^[link]
```
# standard
f(3 + 2) + 1

# non-standard
f (3 + 2) + 1
```
If the first argument to a method begins with an open parenthesis, always use parentheses in the method invocation. For example, write f((3 + 2) + 1). ^[link]

Favor the use of Array#join over Array#* with ^[link] a string argument.

# standard
%w(one two three).join(', ')
# => 'one, two, three'

# non-standard
%w(one two three) * ', '
# => 'one, two, three'

Use [*var] or Array() instead of explicit Array check, when dealing with a variable you want to treat as an Array, but you're not certain it's an array. ^[link]

# standard
[*paths].each { |path| do_something(path) }

# non-standard
paths = [paths] unless paths.is_a? Array
paths.each { |path| do_something(path) }

# non-standard (and a bit more readable)
Array(paths).each { |path| do_something(path) }

Use ranges or Comparable#between? instead of comparison logic. ^[link]

# standard
do_something if (1000..2000).include?(x)

# standard
do_something if x.between?(1000, 2000)

# non-standard
do_something if x >= 1000 && x <= 2000

Favor the use of predicate methods to explicit comparisons with ==. Numeric comparisons are OK. ^[link]

# standard
if x.even?
end

if x.odd?
end

if x.nil?
end

if x.zero?
end

if x == 0
end

# non-standard
if x % 2 == 0
end

if x % 2 == 1
end

if x == nil
end

Don't do explicit non-nil checks unless you're dealing with boolean values. ^[link]

# standard
do_something if something

# standard
def value_set?
  @some_boolean.present?
end

# non-standard
do_something if !something.nil?
do_something if something != nil

Avoid use of nested conditionals for flow of control. ^[link]

Prefer a guard clause when you can assert invalid data.

# standard
def compute_thing(thing)
  return unless thing[:foo]
  update_with_bar(thing[:foo])
  return re_compute(thing) unless thing[:foo][:bar]
  partial_compute(thing)
end

# non-standard
def compute_thing(thing)
  if thing[:foo]
    update_with_bar(thing)
    if thing[:foo][:bar]
      partial_compute(thing)
    else
      re_compute(thing)
    end
  end
end

Prefer next in loops instead of conditional blocks.

# standard
[0, 1, 2, 3].each do |item|
  next unless item > 1
  puts item
end

# non-standard
[0, 1, 2, 3].each do |item|
  if item > 1
    puts item
  end
end

Naming

Use snake_case for symbols, methods and variables. ^[link]

# standard
:some_symbol

def some_method
  ...
end

# non-standard
:'some symbol'
:SomeSymbol
:someSymbol

someVar = 5

def someMethod
  ...
end

def SomeMethod
 ...
end

Use CamelCase for classes and modules. (Keep acronyms like HTTP, RFC, XML uppercase.) ^[link]

# standard
class SomeClass
  ...
end

class SomeXML
  ...
end

# non-standard
class Someclass
  ...
end

class Some_Class
  ...
end

class SomeXml
  ...
end

Use snake_case for naming files, e.g. hello_world.rb. ^[link]
Use snake_case for naming directories, e.g. lib/hello_world/hello_world.rb. ^[link]
Aim to have just a single class/module per source file. Name the file name as the class/module, but replacing CamelCase with snake_case. ^[link]

Use SCREAMING_SNAKE_CASE for other constants. ^[link]

# standard
SOME_CONST = 5

# non-standard
SomeConst = 5

The names of predicate methods should end in a question mark. (i.e. Array#empty?). Methods that don't return a boolean, shouldn't end in a question mark. ^[link]

The names of potentially dangerous methods (i.e. methods that modify self or the arguments, exit! (doesn't run the finalizers like exit does), etc.) should end with an exclamation mark if there exists a safe version of that dangerous method. ^[link]

# standard
class Person
  def update
  end
end

# standard
class Person
  def update!
  end

  def update
  end
end

# non-standard - there is no matching 'safe' method
class Person
  def update!
  end
end

Define the non-bang (safe) method in terms of the bang (dangerous) one if possible. ^[link]

class Array
  def flatten_once!
    res = []

    each do |e|
      [*e].each { |f| res << f }
    end

    replace(res)
  end

  def flatten_once
    dup.flatten_once!
  end
end

Prefer map over collect, detect over find, select over find_all, and size over length.

Use reduce over inject if the result is a single object. Use inject over reduce if the result is an enumeration. ^[link]

Don't use count as a substitute for size. ^[link]

# standard
some_hash.size

# non-standard
some_hash.count

Use flat_map instead of map + flatten. ^[link]

# standard
all_songs = users.flat_map(&:songs).uniq

# non-standard
all_songs = users.map(&:songs).flatten.uniq

Use reverse_each instead of reverse.each. ^[link]

# standard
array.reverse_each { ... }

# non-standard
array.reverse.each { ... }

Comments

Write self-documenting code and ignore the rest of this section. ^[link]
Use one space between the leading # character of the comment and the text of the comment. ^[link]
Comments longer than a word are capitalized and use punctuation. Use one space after periods. ^[link]

No superfluous comments! ^[link]

# non-standard
counter += 1 # Increments counter by one.

Keep existing comments up-to-date. An outdated comment is worse than no comment at all. ^[link]
Avoid writing comments to explain bad code. Refactor the code to make it self-explanatory. (Do or do not - there is no try. --Yoda) ^[link]

Comment Annotations

Annotations should usually be written on the line immediately above the relevant code. ^[link]
The annotation keyword is followed by a colon and a space, then a note describing the problem. ^[link]

If multiple lines are required to describe the problem, subsequent lines should not be indented. ^[link]

def bar
  # FIXME: This has crashed occasionally since v3.2.1. It may
  # be related to the BarBazUtil upgrade.
  baz(:quux)
end

In cases where the problem is so obvious that any documentation would be redundant, annotations may be left at the end of the offending line with no note. This usage should be the exception and not the rule. ^[link]
```
def bar
  sleep 100 # OPTIMIZE
end
```
Use TODO to note missing features or functionality that should be added at a later date. ^[link]
Use FIXME to note broken code that needs to be fixed. ^[link]
Use OPTIMIZE to note slow or inefficient code that may cause performance problems. ^[link]
Use HACK to note code smells where questionable coding practices were used and should be refactored away. ^[link]
Use REVIEW to note anything that should be looked at to confirm it is working as intended. For example: REVIEW: Are we sure this is how the client does X currently? ^[link]
Use other custom annotation keywords if it feels appropriate, but be sure to document them in your project's README or similar. ^[link]

Classes & Modules

Use a consistent structure in your class definitions. ^[link]

class Person
  # extend and include go first
  extend SomeModule
  include AnotherModule

  # inner classes
  CustomErrorKlass = Class.new(StandardError)

  # constants are next
  SOME_CONSTANT = 20

  # afterwards we have attribute macros
  attr_reader :name

  # followed by other macros (if any)
  validates :name

  # public class methods are next in line
  class << self
    def some_method
    end
  end

  # followed by public instance methods
  def some_method
  end

  # protected and private methods are grouped near the end
  protected

  def some_protected_method
  end

  private

  def some_private_method
  end
end

Prefer modules to classes with only class methods. Classes should be used only when it makes sense to create instances out of them. ^[link]

# standard
module SomeClass
  module_function

  def some_method
    # body omitted
  end

  def some_other_method
  end
end

# non-standard
class SomeClass
  def self.some_method
    # body omitted
  end

  def self.some_other_method
  end
end

Declare module namespaces separately. ^[link]

# standard
module Namespace
  class SomeClass
    # body omitted
  end
end

# non-standard
class Namespace::SomeClass
  # body omitted
end

Favor the use of module_function over extend self when you want to turn a module's instance methods into class methods. ^[link]

# standard
module Utilities
  module_function

  def parse_something(string)
    # do stuff here
  end

  def other_utility_method(number, string)
    # do some more stuff
  end
end

# non-standard
module Utilities
  extend self

  def parse_something(string)
    # do stuff here
  end

  def other_utility_method(number, string)
    # do some more stuff
  end
end

Use the attr family of functions to define trivial accessors or mutators. ^[link]

# non-standard
class Person
  def initialize(first_name, last_name)
    @first_name = first_name
    @last_name = last_name
  end

  def first_name
    @first_name
  end

  def last_name
    @last_name
  end
end

# standard
class Person
  attr_reader :first_name, :last_name

  def initialize(first_name, last_name)
    @first_name = first_name
    @last_name = last_name
  end
end

Always supply a proper to_s method for classes that represent domain objects. ^[link]

class Person
  attr_accessor :first_name, :last_name

  def initialize(first_name, last_name)
    self.first_name = first_name
    self.last_name = last_name
  end

  def to_s
    "#{first_name} #{last_name}"
  end
end

Prefer duck-typing over inheritance, assuming there are no common implementations of methods. ^[link]

# standard
class Duck
  def speak
    puts 'Quack! Quack'
  end
end

class Dog
  def speak
    puts 'Bau! Bau!'
  end
end

# non-standard
class Animal
  # abstract method
  def speak
  end
end

class Duck < Animal
  def speak
    puts 'Quack! Quack'
  end
end

class Dog < Animal
  def speak
    puts 'Bau! Bau!'
  end
end

Avoid the usage of class (@@) variables. ^[link]

class Parent
  @@class_var = 'parent'

  def self.print_class_var
    puts @@class_var
  end
end

class Child < Parent
  @@class_var = 'child'
end

Parent.print_class_var # => will print "child"

Assign proper visibility levels to methods (private, protected) in accordance with their intended usage. ^[link]
Indent the public, protected, and private methods as much the method definitions they apply to. Leave one blank line above the visibility modifier and one blank line below in order to emphasize that it applies to all methods below it. ^[link]
```
class SomeClass
  def public_method
    # ...
  end

  private

  def private_method
    # ...
  end

  def another_private_method
    # ...
  end
end
```

Use class << self to define singleton methods. ^[link]

class TestClass
  # standard
  class << self
    def first_method
      # body omitted
    end

    def second_method_etc
      # body omitted
    end
  end

  # non-standard
  def self.some_other_method
    # body omitted
  end

  # non-standard
  def TestClass.some_method
    # body omitted
  end
end

Exceptions

Signal exceptions using the fail method. Use raise only when catching an exception and re-raising it (because here you're not failing, but explicitly and purposefully raising an exception). ^[link]
```
begin
  fail 'Oops'
rescue => error
  raise if error.message != 'Oops'
end
```
Don't specify RuntimeError explicitly in the two argument version of fail/raise. ^[link]
```
# standard
fail 'message'

# non-standard
fail RuntimeError, 'message'
```
Prefer supplying an exception class and a message as two separate arguments to fail/raise, instead of an exception instance. ^[link]
```
# standard
fail SomeException, 'message'

# non-standard
fail SomeException.new('message')
```

Never return from an ensure block. ^[link]

def foo
  begin
    fail
  ensure
    return 'very bad idea'
  end
end

Use implicit begin blocks where possible. ^[link]

# standard
def foo
  # main logic goes here
rescue
  # failure handling goes here
end

# non-standard
def foo
  begin
    # main logic goes here
  rescue
    # failure handling goes here
  end
end

Mitigate the proliferation of begin blocks by using contingency methods ^[link]

# standard
def with_io_error_handling
   yield
rescue IOError
  # handle IOError
end

with_io_error_handling { something_that_might_fail }

with_io_error_handling { something_else_that_might_fail }

# non-standard
begin
  something_that_might_fail
rescue IOError
  # handle IOError
end

begin
  something_else_that_might_fail
rescue IOError
  # handle IOError
end

Don't suppress exceptions. ^[link]

# non-standard
do_something rescue nil

# non-standard
begin
  # an exception occurs here
rescue SomeError
  # the rescue clause does absolutely nothing
end

Always specify an exception type in the rescue clause. ^[link]

# standard
def foo
  read_file
rescue Errno::ENOENT => e
  handle_error(e)
end

Don't use exceptions for flow of control. ^[link]

# standard
if d.zero?
  puts 'Cannot divide by 0!'
else
  n / d
end

# non-standard
begin
  n / d
rescue ZeroDivisionError
  puts 'Cannot divide by 0!'
end

Release external resources obtained by your program in an ensure block. ^[link]

f = File.open('testfile')
begin
  # .. process
rescue
  # .. handle error
ensure
  f.close if f
end

Favor the use of exceptions for the standard library over introducing new exception classes. ^[link]

Collections

Prefer literal array and hash creation notation (unless you need to pass parameters to their constructors, that is). ^[link]
```
# standard
arr = []
hash = {}

# non-standard
arr = Array.new
hash = Hash.new
```
Prefer %w to the literal array syntax when you need an array of words. Apply this rule only to arrays with two or more elements. ^[link]
```
# standard
states = %w(draft open closed)

# non-standard
states = ['draft', 'open', 'closed']
```
Prefer %i to the literal array syntax when you need an array of symbols. Apply this rule only to arrays with two or more elements. ^[link]
```
# standard
states = %i(draft open closed)

# non-standard
states = [:draft, :open, :closed]
```
Avoid comma after the last item of an Array or Hash literal, especially when the items are not on separate lines. ^[link]
```
# standard
values = [1001, 2020, 3333]

# non-standard
values = [1001, 2020, 3333, ]
```
When accessing the first or last element from an array, prefer first or last over [0] or [-1]. ^[link]
Use Set instead of Array when dealing with unique elements. ^[link]

Prefer symbols instead of strings as hash keys. ^[link]

# standard
hash = { :one => 1, :two => 2, :three => 3 }

# non-standard
hash = { 'one' => 1, 'two' => 2, 'three' => 3 }

Use hash rockets instead of Ruby 1.9 symbol notation. ^[link]

# standard
hash = { :one => 1, :two => 2, :three => 3 }

# non-standard
hash = { one: 1, two: 2, three: 3 }

Avoid the use of mutable objects as hash keys. ^[link]
Use Hash#key? instead of Hash#has_key? and Hash#value? instead of Hash#has_value?. As noted here by Matz, the longer forms are considered deprecated. ^[link]
```
# standard
hash.key?(:test)
hash.value?(value)

# non-standard
hash.has_key?(:test)
hash.has_value?(value)
```

Use Hash#fetch when dealing with hash keys that should be present. ^[link]

heroes = { :batman => 'Bruce Wayne', :superman => 'Clark Kent' }

# standard
heroes.fetch(:supermann) # raises a KeyError making the problem obvious

# non-standard
heroes[:batman] # => "Bruce Wayne"
heroes[:supermann] # => nil

Introduce default values for hash keys via Hash#fetch as opposed to using custom logic. ^[link]
```
# standard
batman.fetch(:is_evil, true) # => false
```

Prefer the use of the block instead of the default value in Hash#fetch. ^[link]

# standard
batman.fetch(:powers) { get_batman_powers }

# non-standard
batman.fetch(:powers, get_batman_powers)

Use Hash#values_at when you need to retrieve several values consecutively from a hash. ^[link]

# standard
email, username = data.values_at('email', 'nickname')

# non-standard
email = data['email']
nickname = data['nickname']

Rely on the fact that as of Ruby 1.9 hashes are ordered. ^[link]
Never modify a collection while traversing it. ^[link]

Strings

Prefer string interpolation instead of string concatenation: ^[link]

# standard
email_with_name = "#{user.name} <#{user.email}>"

# non-standard
email_with_name = user.name + ' <' + user.email + '>'

Use single quotes by default ^[link]

# standard
name = 'Bozhidar'

# non-standard
name = "Bozhidar"

Regular Expressions

Don't use regular expressions if you just need plain text search in string: string['text'] ^[link]

For simple constructions you can use regexp directly through string index. ^[link]

match = string[/regexp/]             # get content of matched regexp
first_group = string[/text(grp)/, 1] # get content of captured group
string[/text (grp)/, 1] = 'replace'  # string => 'text replace'

Use non-capturing groups when you don't use captured result of parentheses. ^[link]
```
/(?:first|second)/ # standard
/(first|second)/   # non-standard
```
Don't use the cryptic Perl-legacy variables denoting last regexp group matches ($1, $2, etc). Use Regexp.last_match[n] instead. ^[link]
```
/(regexp)/ =~ string
...

# standard
process Regexp.last_match[1]

# non-standard
process $1
```

Avoid using numbered groups as it can be hard to track what they contain. Named groups can be used instead. ^[link]

# standard
/(?<meaningful_var>regexp)/ =~ string
...
process meaningful_var

# non-standard
/(regexp)/ =~ string
...
process Regexp.last_match[1]

Character classes have only a few special characters you should care about: ^, -, \, ], so don't escape . or brackets in []. ^[link]
Be careful with ^ and $ as they match start/end of line, not string endings. If you want to match the whole string use: \A and \z (not to be confused with \Z which is the equivalent of /\n?\z/). ^[link]
```
string = "some injection\nusername"
string[/^username$/]   # matches
string[/\Ausername\z/] # doesn't match
```

Use x modifier for complex regexps. This makes them more readable and you can add some useful comments. Just be careful as spaces are ignored. ^[link]

regexp = /
  start         # some text
  \s            # white space char
  (group)       # first group
  (?:alt1|alt2) # some alternation
  end
/x

For complex replacements sub/gsub can be used with block or hash. ^[link]

Percent Literals

Use %()(it's a shorthand for %Q) for single-line strings which require both interpolation and embedded double-quotes. For multi-line strings, prefer heredocs. ^[link]

# standard (requires interpolation, has quotes, single line)
%(<tr><td class="name">#{name}</td>)

# non-standard (no interpolation needed)
%(<div class="text">Some text</div>)
# should be '<div class="text">Some text</div>'

# non-standard (no double-quotes)
%(This is #{quality} style)
# should be "This is #{quality} style"

# non-standard (multiple lines)
%(<div>\n<span class="big">#{exclamation}</span>\n</div>)
# should be a heredoc.

Avoid %q unless you have a string with both ' and " in it. Regular string literals are more readable and should be preferred unless a lot of characters would have to be escaped in them. ^[link]

# standard
name = 'Bruce Wayne'
time = "8 o'clock"
question = '"What did you say?"'

# non-standard
name = %q(Bruce Wayne)
time = %q(8 o'clock)
question = %q("What did you say?")

Use %r only for regular expressions matching more than one '/' character. ^[link]

# standard
%r(^/blog/2011/(.*)$)

# non-standard
%r(\s+)

# non-standard
%r(^/(.*)$)
# should be /^\/(.*)$/

Avoid the use of %x unless you're going to invoke a command with backquotes in it(which is rather unlikely). ^[link]
```
# standard
date = `date`
echo = %x(echo `date`)

# non-standard
date = %x(date)
```
Avoid the use of %s. It seems that the community has decided :"some string" is the preferred way to create a symbol with spaces in it. ^[link]
Prefer () as delimiters for all % literals, except %r. Since braces often appear inside regular expressions in many scenarios a less common character like { might be a better choice for a delimiter, depending on the regexp's content. ^[link]
```
# standard
%w(one two three)
%q("Test's king!", John said.)

# non-standard
%w[one two three]
%q{"Test's king!", John said.}
```

Misc (and still important)

Code in a functional way, avoiding mutation when that makes sense. ^[link]
Avoid methods longer than 1 line of code inside the def end block. ^[link]
Avoid hashes as optional parameters. ^[link]
Avoid parameter lists longer than three parameters. ^[link]

Use module instance variables instead of global variables. ^[link]

# standard
module Foo
  class << self
    attr_accessor :bar
  end
end

Foo.bar = 1

# non-standard
$foo_bar = 1

Avoid alias when alias_method will do. ^[link]
Use OptionParser for parsing complex command line options and ruby -s for trivial command line options. ^[link]
Prefer Time.now over Time.new when retrieving the current system time. ^[link]
Do not mutate arguments unless that is the purpose of the method. ^[link]
Avoid more than three levels of block nesting. ^[link]

Name		Name	Last commit message	Last commit date
Latest commit History 514 Commits
.gitattributes		.gitattributes
CONTRIBUTING.md		CONTRIBUTING.md
README.md		README.md

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Repository files navigation

The Ruby Style Guide

Source Code Layout

Syntax

Naming

Comments

Comment Annotations

Classes & Modules

Exceptions

Collections

Strings

Regular Expressions

Percent Literals

Misc (and still important)

About

Releases

Packages

habanerohq/ruby-style-guide

Folders and files

Latest commit

History

Repository files navigation

The Ruby Style Guide

Source Code Layout

Syntax

Naming

Comments

Comment Annotations

Classes & Modules

Exceptions

Collections

Strings

Regular Expressions

Percent Literals

Misc (and still important)

About

Resources

Stars

Watchers

Forks

Releases

Packages 0

Packages