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Ruby хэлний код бичих зөвлөмж

Эх сурвалж: ruby-style-guide

Эх код

Nearly everybody is convinced that every style but their own is ugly and unreadable. Leave out the "but their own" and they're probably right...
-- Jerry Coffin (on indentation)

  • Use UTF-8 as the source file encoding.

  • Догол мөр бүрт 2 хоосон зай авах

    # сайн
def some_method
  do_something
end

# муу - 4 хоосон зай
def some_method
    do_something
end

  • Use Unix-style line endings. (*BSD/Solaris/Linux/OSX users are covered by default, Windows users have to be extra careful.)

    • If you're using Git you might want to add the following configuration setting to protect your project from Windows line endings creeping in:

      $ git config --global core.autocrlf true

  • Операторууд, {, } хаалтнуудын өмнө болон ард, таслал, тодорхойлох цэг, цэгтэй таслалын ард хоосон зай ав. Хоосон зайг зөв ашигласнаар кодыг илүү ойлгомжтой харагдуулдаг.

    sum = 1 + 2
a, b = 1, 2
1 > 2 ? true : false; puts 'Hi'
[1, 2, 3].each { |e| puts e }

    Дээрх зөвлөмжтэй зөрчилдсөн ганц тохиолдол нь зэрэг дэвшүүлэх үйлдэл дээр хоосон зай ашиглаж болохгүй:

    # муу
e = M * c ** 2

# сайн
e = M * c**2

  • (, [ нээх хаалтуудын ард, ], ) хаах хаалтуудын өмнө хоосон зай хэрэггүй

    some(arg).other
[1, 2, 3].length

  • case болон when-ий хооронд догол мөр ав.

    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

kind = case year
       when 1850..1889 then 'Blues'
       when 1890..1909 then 'Ragtime'
       when 1910..1929 then 'New Orleans Jazz'
       when 1930..1939 then 'Swing'
       when 1940..1950 then 'Bebop'
       else 'Jazz'
       end

  • Функциуд болон чухал кодуудын хооронд догол мөр авна.

    def some_method
  data = initialize(options)

  data.manipulate!

  data.result
end

def some_method
  result
end

  • Функц руу дамжуулж байгаа параметрууд нь хэт их бол параметруудыг догол мөрүүдэд хувааж, функцын дуудалттай зэрэгцүүлнэ.

    # муу (мөр нь хэт урт байна)
def send_mail(source)
  Mailer.deliver(to: '[email protected]', from: '[email protected]', subject: 'Important message', body: source.text)
end

# муу (1 догол мөртэй)
def send_mail(source)
  Mailer.deliver(
    to: '[email protected]',
    from: '[email protected]',
    subject: 'Important message',
    body: source.text)
end

# муу (2 догол мөртэй)
def send_mail(source)
  Mailer.deliver(
      to: '[email protected]',
      from: '[email protected]',
      subject: 'Important message',
      body: source.text)
end

# сайн (догол мөр нь функц дуудалттай зэрэгцээ)
def send_mail(source)
  Mailer.deliver(to: '[email protected]',
                 from: '[email protected]',
                 subject: 'Important message',
                 body: source.text)
end

  • API-н баримт бичгэнд RDoc-н зөвлөмжүүдийг ашигла. Функц болон түүний тайлбарын хооронд догол мөр битгий ав.

  • Мөрөнд хамгийн ихдээ 80-н тэмдэгтийг багтаа.

  • Avoid trailing whitespace.

Бичиглэл

  • Хэрэв функц чинь аргументтэй бол хаалт ашигла, үгүй бол хаалт битгий ашигла

    def some_method
  # код
end

def some_method_with_arguments(arg1, arg2)
  # код
end

  • Never use for, unless you know exactly why. Most of the time iterators should be used instead. for is implemented in terms of each (so you're adding a level of indirection), but with a twist - for doesn't introduce a new scope (unlike each) and variables defined in its block will be visible outside it.

    arr = [1, 2, 3]

# муу
for elem in arr do
  puts elem
end

# сайн
arr.each { |elem| puts elem }

  • Олон мөрүүдээс тогтож байгаа if/unless нөхцөлүүдийн ард then түлхүүр үгийг битгий ашигла

    # муу
if some_condition then
  # код
end

# сайн
if some_condition
  # код
end

  • if/then/else/end нөхцөлийн (?:) оронд гурвалсан нөхцөл ашигла.

    # муу
result = if some_condition then something else something_else end

# сайн
result = some_condition ? something : something_else

  • 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.

    # bad
some_condition ? (nested_condition ? nested_something : nested_something_else) : something_else

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

  • if x: ...-ийг хэзээ ч бүү ашигла, энэ нь Ruby 1.9 дээр дэмжигдэхээ больсон. Оронд нь гурвалсан операторыг ашигла.

    # муу
result = if some_condition: something else something_else end

# сайн
result = some_condition ? something : something_else

  • if x; ...-ийг хэзээ ч бүү ашигла. Оронд нь гурвалсан операторыг ашигла.

  • when x; ... үүнийг хэзээ ч бүү ашигла. Өмнөх зөвлөмжийг харна уу.

  • Булийн илэрхийллийн үед &&/||-ийг, удирдлагын урсгалын үед and/or-ийг ашигла. (Практик туршлага: Хэрэв чамд гадуур хаалт хэрэглэх шаардлага гараад байвал чи буруу л оператороо ашиглаад байна даа.)

    # булийн нөхцөл
if some_condition && some_other_condition
  do_something
end

# удирлагын урсгал
document.saved? or document.save!

  • Олон мөр шалгалтанд ?: (гурвалсан оператор)-г ашиглахаас зайлсхий, оронд нь if/unless-ийг ашигла.

  • Favor modifier if/unless usage when you have a single-line body. Өөр нэг сайн бичиглэл бол удирдлагын урсгалын and/or-ийг ашиглах явдал юм.

    # муу
if some_condition
  do_something
end

# сайн
do_something if some_condition

# өөр нэг хувилбар
some_condition and do_something

  • Сөрөг нөхцөл шалгах үед if-ийн оронд unless-ийг ашиглах нь тохиромжтой (эсвэл or нөхцлийг ашиглаарай).

    # муу
do_something if !some_condition

# сайн
do_something unless some_condition

# өөр нэг хувилбар
some_condition or do_something

  • unless-ийг else-тэй цуг бүү ашигла. Эерэг тохиолдлыг нь эхэлж шалга.

    # муу
unless success?
  puts 'failure'
else
  puts 'success'
end

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

  • Don't use parentheses around the condition of an if/unless/while, unless the condition contains an assignment (see "Using the return value of =" below).

    # bad
if (x > 10)
  # body omitted
end

# good
if x > 10
  # body omitted
end

# ok
if (x = self.next_value)
  # body omitted
end

  • Omit parentheses around parameters for methods that are part of an internal DSL (e.g. Rake, Rails, RSpec), methods that are with "keyword" status in Ruby (e.g. attr_reader, puts) and attribute access methods. Use parentheses around the arguments of all other method invocations.

    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)

  • 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.

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

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

# bad
names.each do |name|
  puts name
end

# good
names.select { |name| name.start_with?("S") }.map { |name| name.upcase }

# bad
names.select do |name|
  name.start_with?("S")
end.map { |name| name.upcase }

    Some will argue that multiline chaining would look OK with the use of {...}, but they should ask themselves - it this code really readable and can't the blocks contents be extracted into nifty methods.

  • Шаардлагагүй үед return ашиглахаас татгалз.

    # муу
def some_method(some_arr)
  return some_arr.size
end

# сайн
def some_method(some_arr)
  some_arr.size
end

  • Функцын параметруудад заяамал утга оноож байгаа бол тэнцүүгийн тэмдэг (=)-н хоёр талд зай авах

    # муу
def some_method(arg1=:default, arg2=nil, arg3=[])
  # кодын хэсэг...
end

# сайн
def some_method(arg1 = :default, arg2 = nil, arg3 = [])
  # кодын хэсэг...
end

    Зарим Ruby номнуудад эхний хувилбарыг санал болгодог ч 2 дахь хувилбарыг нь практикт илүү дэмждэг (бас илүү уншихад эвтэйхэн).

  • Шаардлагагүй бол мөр үргэлжлүүлэгч (\)-г битгий ашигла. Туршлагаас харахад мөр үргэлжлүүлэгчийг ашиглахгүй байсан нь дээр байдаг.

    # муу
result = 1 - \
         2

# сайн (гэхдээ, ашиглах хэрэггүй)
result = 1 \
         - 2

  • Using the return value of = (an assignment) is ok, but surround the assignment with parenthesis.

    # good - shows intented use of assignment
if (v = array.grep(/foo/)) ...

# bad
if v = array.grep(/foo/) ...

# also good - shows intended use of assignment and has correct precedence.
if (v = self.next_value) == "hello" ...

  • Хувьсагчид дахин анхны утга оноохдоо ||=-г ашигла.

    # Хэрэв нэр нь nil эсвэл false бол уг нэрэнд Bozhidar гэсэн утга онооно
name ||= 'Bozhidar'

  • ||=-г бүүлэн төрлийн хувьсагчид ашиглаж болохгүй. (Хэрэв хувьсагчийн утга нь false байвал юу болох бол.)

    # муу - хэрэв false-л байх юм бол true-г онооно
enabled ||= true

# сайн
enabled = true if enabled.nil?

  • Avoid using Perl-style special variables (like $0-9, `$``, etc. ). They are quite cryptic and their use in anything but one-liner scripts is discouraged.

  • Never put a space between a method name and the opening parenthesis.

    # bad
f (3 + 2) + 1

# good
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).

  • Always run the Ruby interpreter with the -w option so it will warn you if you forget either of the rules above!

  • When the keys of your hash are symbols use the Ruby 1.9 hash literal syntax.

    # bad
hash = { :one => 1, :two => 2 }

# good
hash = { one: 1, two: 2 }

  • Use the new lambda literal syntax.

    # bad
lambda = lambda { |a, b| a + b }
lambda.call(1, 2)

# good
lambda = ->(a, b) { a + b }
lambda.(1, 2)

  • Ашиглагдахгүй блокын хувьсагчийн нэрний оронд _-г ашигла.

    # муу
result = hash.map { |k, v| v + 1 }

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

Нэршил

The only real difficulties in programming are cache invalidation and naming things.
-- Phil Karlton

  • Use snake_case for methods and variables.

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

  • Use SCREAMING_SNAKE_CASE for other constants.

  • The names of predicate methods (methods that return a boolean value) should end in a question mark. (i.e. Array#empty?).

  • The names of potentially "dangerous" methods (i.e. methods that modify self or the arguments, exit!, etc.) should end with an exclamation mark.

  • When using reduce with short blocks, name the arguments |a, e| (accumulator, element).

  • When defining binary operators, name the argument other.

    def +(other)
  # body omitted
end

  • Prefer map over collect, find over detect, select over find_all, reduce over inject and size over length. This is not a hard requirement; if the use of the alias enhances readability, it's ok to use it. The rhyming methods are inherited from Smalltalk and are not common in other programming languages. The reason the use of select is encouraged over find_all is that it goes together nicely with reject and its name is pretty self-explanatory.

Тайлбар

Good code is its own best documentation. As you're about to add a comment, ask yourself, "How can I improve the code so that this comment isn't needed?" Improve the code and then document it to make it even clearer.
-- Steve McConnell

  • Write self-documenting code and ignore the rest of this section. Seriously!

  • Comments longer than a word are capitalized and use punctuation. Use one space after periods.

  • Avoid superfluous comments.

    # bad
counter += 1 # increments counter by one

  • Keep existing comments up-to-date. No comment is better than an outdated comment.

  • Avoid writing comments to explain bad code. Refactor the code to make it self-explanatory. (Do or do not - there is no try.)

Тэмдэглэгээ

  • Annotations should usually be written on the line immediately above the relevant code.

  • The annotation keyword is followed by a colon and a space, then a note describing the problem.

  • If multiple lines are required to describe the problem, subsequent lines should be indented two spaces after the #.

    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.

    def bar
  sleep 100 # OPTIMIZE
end

  • Use TODO to note missing features or functionality that should be added at a later date.

  • Use FIXME to note broken code that needs to be fixed.

  • Use OPTIMIZE to note slow or inefficient code that may cause performance problems.

  • Use HACK to note code smells where questionable coding practices were used and should be refactored away.

  • 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?

  • Use other custom annotation keywords if it feels appropriate, but be sure to document them in your project's README or similar.

Класс

  • When designing class hierarchies make sure that they conform to the Liskov Substitution Principle.

  • Try to make your classes as [SOLID](http://en.wikipedia.org/wiki/SOLID_(object-oriented_design\)) as possible.

  • Always supply a proper to_s method for classes that represent domain objects.

    class Person
  attr_reader :first_name, :last_name

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

  def to_s
    "#@first_name #@last_name"
  end
end

  • Use the attr family of functions to define trivial accessors or mutators.

    # bad
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

# good
class Person
  attr_reader :first_name, :last_name

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

  • Consider adding factory methods to provide additional sensible ways to create instances of a particular class.

    class Person
  def self.create(options_hash)
    # body omitted
  end
end

  • Prefer duck-typing over inheritance.

    # bad
class Animal
  # abstract method
  def speak
  end
end

# extend superclass
class Duck < Animal
  def speak
    puts 'Quack! Quack'
  end
end

# extend superclass
class Dog < Animal
  def speak
    puts 'Bau! Bau!'
  end
end

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

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

  • Avoid the usage of class (@@) variables due to their "nasty" behavior in inheritance.

    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"

    As you can see all the classes in a class hierarchy actually share one class variable. Class instance variables should usually be preferred over class variables.

  • Assign proper visibility levels to methods (private, protected) in accordance with their intended usage. Don't go off leaving everything public (which is the default). After all we're coding in Ruby now, not in Python.

  • Indent the public, protected, and private methods as much the method definitions they apply to. Leave one blank line above them.

    class SomeClass
  def public_method
    # ...
  end

  private
  def private_method
    # ...
  end
end

  • Use def self.method to define singleton methods. This makes the methods more resistant to refactoring changes.

    class TestClass
  # bad
  def TestClass.some_method
    # body omitted
  end

  # good
  def self.some_other_method
    # body omitted
  end

  # Also possible and convenient when you
  # have to define many singleton methods.
  class << self
    def first_method
      # body omitted
    end

    def second_method_etc
      # body omitted
    end
  end
end

Exceptions

  • Don't suppress exceptions.

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

  • Don't use exceptions for flow of control.

    # bad
begin
  n / d
rescue ZeroDivisionError
  puts "Cannot divide by 0!"
end

# good
if n.zero?
  puts "Cannot divide by 0!"
else
  n / d

  • Avoid rescuing the Exception class.

    # bad
begin
  # an exception occurs here
rescue
  # exception handling
end

# still bad
begin
  # an exception occurs here
rescue Exception
  # exception handling
end

  • Put more specific exceptions higher up the rescue chain, otherwise they'll never be rescued from.

    # bad
begin
  # some code
rescue Exception => e
  # some handling
rescue StandardError => e
  # some handling
end

# good
begin
  # some code
rescue StandardError => e
  # some handling
rescue Exception => e
  # some handling
end

  • Release external resources obtained by your program in an ensure block.

    f = File.open("testfile")
begin
  # .. process
rescue
  # .. handle error
ensure
  f.close unless f.nil?
end

  • Favor the use of exceptions for the standard library over introducing new exception classes.

Collections

  • Prefer %w to the literal array syntax when you need an array of strings.

    # bad
STATES = ['draft', 'open', 'closed']

# good
STATES = %w(draft open closed)

  • Avoid the creation of huge gaps in arrays.

    arr = []
arr[100] = 1 # now you have an array with lots of nils

  • Use Set instead of Array when dealing with unique elements. Set implements a collection of unordered values with no duplicates. This is a hybrid of Array's intuitive inter-operation facilities and Hash's fast lookup.

  • Use symbols instead of strings as hash keys.

    # bad
hash = { 'one' => 1, 'two' => 2, 'three' => 3 }

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

  • Avoid the use of mutable object as hash keys.

  • Use the new 1.9 literal hash syntax in preference to the hashrocket syntax.

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

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

  • Rely on the fact that hashes in 1.9 are ordered.

  • Never modify a collection while traversing it.

Тэмдэгт мөр

  • Prefer string interpolation instead of string concatenation:

    # bad
email_with_name = user.name + ' <' + user.email + '>'

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

  • Prefer single-quoted strings when you don't need string interpolation or special symbols such as \t, \n, ', etc.

    # bad
name = "Bozhidar"

# good
name = 'Bozhidar'

  • Don't use {} around instance variables being interpolated into a string.

    class Person
  attr_reader :first_name, :last_name

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

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

  # good
  def to_s
    "#@first_name #@last_name"
  end
end

  • Avoid using String#+ when you need to construct large data chunks. Instead, use String#<<. Concatenation mutates the string instance in-place and is always faster than String#+, which creates a bunch of new string objects.

    # good and also fast
html = ''
html << '<h1>Page title</h1>'

paragraphs.each do |paragraph|
  html << "<p>#{paragraph}</p>"
end

Энгийн илэрхийлэл

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

  • For simple constructions you can use regexp directly through string index.

    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 parenthesis.

    /(first|second)/   # bad
/(?:first|second)/ # good

  • Avoid using $1-9 as it can be hard to track what they contain. Named groups can be used instead.

    # bad
/(regexp)/ =~ string
...
process $1

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

  • Character classes have only few special characters you should care about: ^, -, \, ], so don't escape . or brackets in [].

  • 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.

    string = "some injection\nusername"
string[/^username$/]   # matches
string[/\Ausername\Z/] # don'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.

    regexp = %r{
  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.

Percent Literals

  • %w тэмдэглэгээг сайн ашигла

    STATES = %w(draft open closed)

  • Use %() for single-line strings which require both interpolation and embedded double-quotes. For multi-line strings, prefer heredocs.

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

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

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

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

  • Use %r only for regular expressions matching more than one '/' character.

    # bad
%r(\s+)

# still bad
%r(^/(.*)$)
# should be /^\/(.*)$/

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

  • Avoid %q, %Q, %x, %s, and %W.

  • Prefer () as delimiters for all % literals.

Metaprogramming

  • Do not mess around in core classes when writing libraries. (Do not monkey patch them.)

Misc

  • Write ruby -w safe code.

  • Avoid hashes as optional parameters. Does the method do too much?

  • Avoid methods longer than 10 LOC (lines of code). Ideally, most methods will be shorter than 5 LOC. Empty lines do not contribute to the relevant LOC.

  • Avoid parameter lists longer than three or four parameters.

  • If you really have to, add "global" methods to Kernel and make them private.

  • Use class instance variables instead of global variables.

    #bad
$foo_bar = 1

#good
class Foo
  class << self
    attr_accessor :bar
  end
end

Foo.bar = 1

  • Avoid alias when alias_method will do.

  • Use OptionParser for parsing complex command line options and ruby -s for trivial command line options.

  • Code in a functional way, avoiding mutation when that makes sense.

  • Avoid needless metaprogramming.

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

  • Avoid more than three levels of block nesting.

  • Be consistent. In an ideal world, be consistent with these guidelines.

  • Use common sense.