module ActiveSupport::Inflector

# File activesupport/lib/active_support/inflector/methods.rb, line 66
def camelize(term, uppercase_first_letter = true)
  string = term.to_s
  if uppercase_first_letter
    string = string.sub(/^[a-z\d]*/) { |match| inflections.acronyms[match] || match.capitalize }
  else
    string = string.sub(/^(?:#{inflections.acronym_regex}(?=\b|[A-Z_])|\w)/) { |match| match.downcase }
  end
  string.gsub!(/(?:_|(\/))([a-z\d]*)/i) { "#{$1}#{inflections.acronyms[$2] || $2.capitalize}" }
  string.gsub!('/'.freeze, '::'.freeze)
  string
end

Converts strings to UpperCamelCase. If the uppercase_first_letter parameter is set to false, then produces lowerCamelCase.

Also converts '/' to '::' which is useful for converting paths to namespaces.

camelize('active_model')                # => "ActiveModel"
camelize('active_model', false)         # => "activeModel"
camelize('active_model/errors')         # => "ActiveModel::Errors"
camelize('active_model/errors', false)  # => "activeModel::Errors"

As a rule of thumb you can think of camelize as the inverse of underscore, though there are cases where that does not hold:

camelize(underscore('SSLError'))        # => "SslError"

# File activesupport/lib/active_support/inflector/methods.rb, line 186
def classify(table_name)
  # strip out any leading schema name
  camelize(singularize(table_name.to_s.sub(/.*\./, ''.freeze)))
end

Creates a class name from a plural table name like Rails does for table names to models. Note that this returns a string and not a Class (To convert to an actual class follow classify with constantize).

classify('ham_and_eggs') # => "HamAndEgg"
classify('posts')        # => "Post"

Singular names are not handled correctly:

classify('calculus')     # => "Calculus"

# File activesupport/lib/active_support/inflector/methods.rb, line 257
def constantize(camel_cased_word)
  names = camel_cased_word.split('::'.freeze)

  # Trigger a built-in NameError exception including the ill-formed constant in the message.
  Object.const_get(camel_cased_word) if names.empty?

  # Remove the first blank element in case of '::ClassName' notation.
  names.shift if names.size > 1 && names.first.empty?

  names.inject(Object) do |constant, name|
    if constant == Object
      constant.const_get(name)
    else
      candidate = constant.const_get(name)
      next candidate if constant.const_defined?(name, false)
      next candidate unless Object.const_defined?(name)

      # Go down the ancestors to check if it is owned directly. The check
      # stops when we reach Object or the end of ancestors tree.
      constant = constant.ancestors.inject(constant) do |const, ancestor|
        break const    if ancestor == Object
        break ancestor if ancestor.const_defined?(name, false)
        const
      end

      # owner is in Object, so raise
      constant.const_get(name, false)
    end
  end
end

Tries to find a constant with the name specified in the argument string.

'Module'.constantize   # => Module
'Foo::Bar'.constantize # => Foo::Bar

The name is assumed to be the one of a top-level constant, no matter whether it starts with “::” or not. No lexical context is taken into account:

C = 'outside'
module M
  C = 'inside'
  C               # => 'inside'
  'C'.constantize # => 'outside', same as ::C
end

NameError is raised when the name is not in CamelCase or the constant is unknown.

# File activesupport/lib/active_support/inflector/methods.rb, line 194
def dasherize(underscored_word)
  underscored_word.tr('_'.freeze, '-'.freeze)
end

Replaces underscores with dashes in the string.

dasherize('puni_puni') # => "puni-puni"

# File activesupport/lib/active_support/inflector/methods.rb, line 224
def deconstantize(path)
  path.to_s[0, path.rindex('::') || 0] # implementation based on the one in facets' Module#spacename
end

Removes the rightmost segment from the constant expression in the string.

deconstantize('Net::HTTP')   # => "Net"
deconstantize('::Net::HTTP') # => "::Net"
deconstantize('String')      # => ""
deconstantize('::String')    # => ""
deconstantize('')            # => ""

See also demodulize.

# File activesupport/lib/active_support/inflector/methods.rb, line 206
def demodulize(path)
  path = path.to_s
  if i = path.rindex('::')
    path[(i+2)..-1]
  else
    path
  end
end

Removes the module part from the expression in the string.

demodulize('ActiveRecord::CoreExtensions::String::Inflections') # => "Inflections"
demodulize('Inflections')                                       # => "Inflections"
demodulize('::Inflections')                                     # => "Inflections"
demodulize('')                                                  # => ""

See also deconstantize.

# File activesupport/lib/active_support/inflector/methods.rb, line 235
def foreign_key(class_name, separate_class_name_and_id_with_underscore = true)
  underscore(demodulize(class_name)) + (separate_class_name_and_id_with_underscore ? "_id" : "id")
end

Creates a foreign key name from a class name. separate_class_name_and_id_with_underscore sets whether the method should put '_' between the name and 'id'.

foreign_key('Message')        # => "message_id"
foreign_key('Message', false) # => "messageid"
foreign_key('Admin::Post')    # => "post_id"

# File activesupport/lib/active_support/inflector/methods.rb, line 123
def humanize(lower_case_and_underscored_word, options = {})
  result = lower_case_and_underscored_word.to_s.dup

  inflections.humans.each { |(rule, replacement)| break if result.sub!(rule, replacement) }

  result.sub!(/\A_+/, ''.freeze)
  result.sub!(/_id\z/, ''.freeze)
  result.tr!('_'.freeze, ' '.freeze)

  result.gsub!(/([a-z\d]*)/i) do |match|
    "#{inflections.acronyms[match] || match.downcase}"
  end

  if options.fetch(:capitalize, true)
    result.sub!(/\A\w/) { |match| match.upcase }
  end

  result
end

Tweaks an attribute name for display to end users.

Specifically, performs these transformations:

• Applies human inflection rules to the argument.

• Deletes leading underscores, if any.

• Removes a “_id” suffix if present.

• Replaces underscores with spaces, if any.

• Downcases all words except acronyms.

• Capitalizes the first word.

The capitalization of the first word can be turned off by setting the :capitalize option to false (default is true).

humanize('employee_salary')              # => "Employee salary"
humanize('author_id')                    # => "Author"
humanize('author_id', capitalize: false) # => "author"
humanize('_id')                          # => "Id"

If “SSL” was defined to be an acronym:

humanize('ssl_error') # => "SSL error"

# File activesupport/lib/active_support/inflector/inflections.rb, line 234
def inflections(locale = :en)
  if block_given?
    yield Inflections.instance(locale)
  else
    Inflections.instance(locale)
  end
end

Yields a singleton instance of Inflector::Inflections so you can specify additional inflector rules. If passed an optional locale, rules for other languages can be specified. If not specified, defaults to :en. Only rules for English are provided.

ActiveSupport::Inflector.inflections(:en) do |inflect|
  inflect.uncountable 'rails'
end

# File activesupport/lib/active_support/inflector/methods.rb, line 328
def ordinal(number)
  abs_number = number.to_i.abs

  if (11..13).include?(abs_number % 100)
    "th"
  else
    case abs_number % 10
      when 1; "st"
      when 2; "nd"
      when 3; "rd"
      else    "th"
    end
  end
end

Returns the suffix that should be added to a number to denote the position in an ordered sequence such as 1st, 2nd, 3rd, 4th.

ordinal(1)     # => "st"
ordinal(2)     # => "nd"
ordinal(1002)  # => "nd"
ordinal(1003)  # => "rd"
ordinal(-11)   # => "th"
ordinal(-1021) # => "st"

# File activesupport/lib/active_support/inflector/methods.rb, line 352
def ordinalize(number)
  "#{number}#{ordinal(number)}"
end

Turns a number into an ordinal string used to denote the position in an ordered sequence such as 1st, 2nd, 3rd, 4th.

ordinalize(1)     # => "1st"
ordinalize(2)     # => "2nd"
ordinalize(1002)  # => "1002nd"
ordinalize(1003)  # => "1003rd"
ordinalize(-11)   # => "-11th"
ordinalize(-1021) # => "-1021st"

# File activesupport/lib/active_support/inflector/transliterate.rb, line 82
def parameterize(string, sep = :unused, separator: '-', preserve_case: false)
  unless sep == :unused
    ActiveSupport::Deprecation.warn("Passing the separator argument as a positional parameter is deprecated and will soon be removed. Use `separator: '#{sep}'` instead.")
    separator = sep
  end
  # Replace accented chars with their ASCII equivalents.
  parameterized_string = transliterate(string)

  # Turn unwanted chars into the separator.
  parameterized_string.gsub!(/[^a-z0-9\-_]+/i, separator)

  unless separator.nil? || separator.empty?
    if separator == "-".freeze
      re_duplicate_separator        = /-{2,}/
      re_leading_trailing_separator = /^-|-$/i
    else
      re_sep = Regexp.escape(separator)
      re_duplicate_separator        = /#{re_sep}{2,}/
      re_leading_trailing_separator = /^#{re_sep}|#{re_sep}$/i
    end
    # No more than one of the separator in a row.
    parameterized_string.gsub!(re_duplicate_separator, separator)
    # Remove leading/trailing separator.
    parameterized_string.gsub!(re_leading_trailing_separator, ''.freeze)
  end
  
  parameterized_string.downcase! unless preserve_case
  parameterized_string
end

Replaces special characters in a string so that it may be used as part of a 'pretty' URL.

parameterize("Donald E. Knuth") # => "donald-e-knuth"
parameterize("^trés|Jolie-- ")  # => "tres-jolie"

To use a custom separator, override the `separator` argument.

parameterize("Donald E. Knuth", separator: '_') # => "donald_e_knuth"
parameterize("^trés|Jolie-- ", separator: '_')  # => "tres_jolie"

To preserve the case of the characters in a string, use the `preserve_case` argument.

parameterize("Donald E. Knuth", preserve_case: true) # => "Donald-E-Knuth"
parameterize("^trés|Jolie-- ", preserve_case: true) # => "tres-Jolie"

# File activesupport/lib/active_support/inflector/methods.rb, line 29
def pluralize(word, locale = :en)
  apply_inflections(word, inflections(locale).plurals)
end

Returns the plural form of the word in the string.

If passed an optional locale parameter, the word will be pluralized using rules defined for that language. By default, this parameter is set to :en.

pluralize('post')             # => "posts"
pluralize('octopus')          # => "octopi"
pluralize('sheep')            # => "sheep"
pluralize('words')            # => "words"
pluralize('CamelOctopus')     # => "CamelOctopi"
pluralize('ley', :es)         # => "leyes"

# File activesupport/lib/active_support/inflector/methods.rb, line 310
def safe_constantize(camel_cased_word)
  constantize(camel_cased_word)
rescue NameError => e
  raise if e.name && !(camel_cased_word.to_s.split("::").include?(e.name.to_s) ||
    e.name.to_s == camel_cased_word.to_s)
rescue ArgumentError => e
  raise unless e.message =~ /not missing constant #{const_regexp(camel_cased_word)}\!$/
end

Tries to find a constant with the name specified in the argument string.

safe_constantize('Module')   # => Module
safe_constantize('Foo::Bar') # => Foo::Bar

The name is assumed to be the one of a top-level constant, no matter whether it starts with “::” or not. No lexical context is taken into account:

C = 'outside'
module M
  C = 'inside'
  C                     # => 'inside'
  safe_constantize('C') # => 'outside', same as ::C
end

nil is returned when the name is not in CamelCase or the constant (or part of it) is unknown.

safe_constantize('blargle')                  # => nil
safe_constantize('UnknownModule')            # => nil
safe_constantize('UnknownModule::Foo::Bar')  # => nil

# File activesupport/lib/active_support/inflector/methods.rb, line 46
def singularize(word, locale = :en)
  apply_inflections(word, inflections(locale).singulars)
end

The reverse of pluralize, returns the singular form of a word in a string.

If passed an optional locale parameter, the word will be singularized using rules defined for that language. By default, this parameter is set to :en.

singularize('posts')            # => "post"
singularize('octopi')           # => "octopus"
singularize('sheep')            # => "sheep"
singularize('word')             # => "word"
singularize('CamelOctopi')      # => "CamelOctopus"
singularize('leyes', :es)       # => "ley"

# File activesupport/lib/active_support/inflector/methods.rb, line 172
def tableize(class_name)
  pluralize(underscore(class_name))
end

Creates the name of a table like Rails does for models to table names. This method uses the pluralize method on the last word in the string.

tableize('RawScaledScorer') # => "raw_scaled_scorers"
tableize('ham_and_egg')     # => "ham_and_eggs"
tableize('fancyCategory')   # => "fancy_categories"

# File activesupport/lib/active_support/inflector/methods.rb, line 162
def titleize(word)
  humanize(underscore(word)).gsub(/\b(?<!['’`])[a-z]/) { |match| match.capitalize }
end

Capitalizes all the words and replaces some characters in the string to create a nicer looking title. titleize is meant for creating pretty output. It is not used in the Rails internals.

titleize is also aliased as titlecase.

titleize('man from the boondocks')   # => "Man From The Boondocks"
titleize('x-men: the last stand')    # => "X Men: The Last Stand"
titleize('TheManWithoutAPast')       # => "The Man Without A Past"
titleize('raiders_of_the_lost_ark')  # => "Raiders Of The Lost Ark"

# File activesupport/lib/active_support/inflector/transliterate.rb, line 60
def transliterate(string, replacement = "?".freeze)
  I18n.transliterate(ActiveSupport::Multibyte::Unicode.normalize(
    ActiveSupport::Multibyte::Unicode.tidy_bytes(string), :c),
      :replacement => replacement)
end

Replaces non-ASCII characters with an ASCII approximation, or if none exists, a replacement character which defaults to “?”.

transliterate('Ærøskøbing')
# => "AEroskobing"

Default approximations are provided for Western/Latin characters, e.g, “ø”, “ñ”, “é”, “ß”, etc.

This method is I18n aware, so you can set up custom approximations for a locale. This can be useful, for example, to transliterate German's “ü” and “ö” to “ue” and “oe”, or to add support for transliterating Russian to ASCII.

In order to make your custom transliterations available, you must set them as the i18n.transliterate.rule i18n key:

# Store the transliterations in locales/de.yml
i18n:
  transliterate:
    rule:
      ü: "ue"
      ö: "oe"

# Or set them using Ruby
I18n.backend.store_translations(:de, i18n: {
  transliterate: {
    rule: {
      'ü' => 'ue',
      'ö' => 'oe'
    }
  }
})

The value for i18n.transliterate.rule can be a simple Hash that maps characters to ASCII approximations as shown above, or, for more complex requirements, a Proc:

I18n.backend.store_translations(:de, i18n: {
  transliterate: {
    rule: ->(string) { MyTransliterator.transliterate(string) }
  }
})

Now you can have different transliterations for each locale:

I18n.locale = :en
transliterate('Jürgen')
# => "Jurgen"

I18n.locale = :de
transliterate('Jürgen')
# => "Juergen"

# File activesupport/lib/active_support/inflector/methods.rb, line 89
def underscore(camel_cased_word)
  return camel_cased_word unless camel_cased_word =~ /[A-Z-]|::/
  word = camel_cased_word.to_s.gsub('::'.freeze, '/'.freeze)
  word.gsub!(/(?:(?<=([A-Za-z\d]))|\b)(#{inflections.acronym_regex})(?=\b|[^a-z])/) { "#{$1 && '_'.freeze }#{$2.downcase}" }
  word.gsub!(/([A-Z\d]+)([A-Z][a-z])/, '\1_\2'.freeze)
  word.gsub!(/([a-z\d])([A-Z])/, '\1_\2'.freeze)
  word.tr!("-".freeze, "_".freeze)
  word.downcase!
  word
end

Makes an underscored, lowercase form from the expression in the string.

Changes '::' to '/' to convert namespaces to paths.

underscore('ActiveModel')         # => "active_model"
underscore('ActiveModel::Errors') # => "active_model/errors"

As a rule of thumb you can think of underscore as the inverse of camelize, though there are cases where that does not hold:

camelize(underscore('SSLError'))  # => "SslError"

# File activesupport/lib/active_support/inflector/methods.rb, line 148
def upcase_first(string)
  string.length > 0 ? string[0].upcase.concat(string[1..-1]) : ''
end

Converts just the first character to uppercase.

upcase_first('what a Lovely Day') # => "What a Lovely Day"
upcase_first('w')                 # => "W"
upcase_first('')                  # => ""