The Inflector transforms words from singular to plural, class names to table names, modularized class names to ones without, and class names to foreign keys. The default inflections for pluralization, singularization, and uncountable words are kept in inflections.rb.

The Rails core team has stated patches for the inflections library will not be accepted in order to avoid breaking legacy applications which may be relying on errant inflections. If you discover an incorrect inflection and require it for your application, you'll need to correct it yourself (explained below).

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Instance Public methods
camelize(lower_case_and_underscored_word, first_letter_in_uppercase = true)

By default, camelizeconverts strings to UpperCamelCase. If the argument to camelizeis set to :lowerthen camelizeproduces lowerCamelCase.

camelizewill also convert '/' to '::' which is useful for converting paths to namespaces.

Examples:

"active_record".camelize                # => "ActiveRecord"
"active_record".camelize(:lower)        # => "activeRecord"
"active_record/errors".camelize         # => "ActiveRecord::Errors"
"active_record/errors".camelize(:lower) # => "activeRecord::Errors"
# File activesupport/lib/active_support/inflector.rb, line 178
def camelize(lower_case_and_underscored_word, first_letter_in_uppercase = true)
  if first_letter_in_uppercase
    lower_case_and_underscored_word.to_s.gsub(/\/(.?)/) { "::#{$1.upcase}" }.gsub(/(?:^|_)(.)/) { $1.upcase }
  else
    lower_case_and_underscored_word.first.downcase + camelize(lower_case_and_underscored_word)[1..-1]
  end
end
classify(table_name)

Create 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 classifywith constantize.)

Examples:

"egg_and_hams".classify # => "EggAndHam"
"posts".classify        # => "Post"

Singular names are not handled correctly:

"business".classify     # => "Busines"
# File activesupport/lib/active_support/inflector.rb, line 320
def classify(table_name)
  # strip out any leading schema name
  camelize(singularize(table_name.to_s.sub(/.*\./, '')))
end
constantize(camel_cased_word)

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

"Module".constantize     # => Module
"Test::Unit".constantize # => Test::Unit

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.rb, line 357
def constantize(camel_cased_word)
  names = camel_cased_word.split('::')
  names.shift if names.empty? || names.first.empty?
  constant = Object
  names.each do |name|
    constant = constant.const_defined?(name) ? constant.const_get(name) : constant.const_missing(name)
  end
  constant
end
dasherize(underscored_word)

Replaces underscores with dashes in the string.

Example:

"puni_puni" # => "puni-puni"
# File activesupport/lib/active_support/inflector.rb, line 218
def dasherize(underscored_word)
  underscored_word.gsub(/_/, '-')
end
demodulize(class_name_in_module)

Removes the module part from the expression in the string.

Examples:

"ActiveRecord::CoreExtensions::String::Inflections".demodulize # => "Inflections"
"Inflections".demodulize                                       # => "Inflections"
# File activesupport/lib/active_support/inflector.rb, line 240
def demodulize(class_name_in_module)
  class_name_in_module.to_s.gsub(/^.*::/, '')
end
foreign_key(class_name, separate_class_name_and_id_with_underscore = true)

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

Examples:

"Message".foreign_key        # => "message_id"
"Message".foreign_key(false) # => "messageid"
"Admin::Post".foreign_key    # => "post_id"
# File activesupport/lib/active_support/inflector.rb, line 333
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
humanize(lower_case_and_underscored_word)

Capitalizes the first word and turns underscores into spaces and strips a trailing “_id”, if any. Like titleize, this is meant for creating pretty output.

Examples:

"employee_salary" # => "Employee salary"
"author_id"       # => "Author"
# File activesupport/lib/active_support/inflector.rb, line 228
def humanize(lower_case_and_underscored_word)
  result = lower_case_and_underscored_word.to_s.dup
  inflections.humans.each { |(rule, replacement)| break if result.gsub!(rule, replacement) }
  result.gsub(/_id$/, "").gsub(/_/, " ").capitalize
end
inflections()

Yields a singleton instance of Inflector::Inflections so you can specify additional inflector rules.

Example:

ActiveSupport::Inflector.inflections do |inflect|
  inflect.uncountable "rails"
end
# File activesupport/lib/active_support/inflector.rb, line 122
def inflections
  if block_given?
    yield Inflections.instance
  else
    Inflections.instance
  end
end
ordinalize(number)

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

Examples:

ordinalize(1)     # => "1st"
ordinalize(2)     # => "2nd"
ordinalize(1002)  # => "1002nd"
ordinalize(1003)  # => "1003rd"
# File activesupport/lib/active_support/inflector.rb, line 388
def ordinalize(number)
  if (11..13).include?(number.to_i % 100)
    "#{number}th"
  else
    case number.to_i % 10
      when 1; "#{number}st"
      when 2; "#{number}nd"
      when 3; "#{number}rd"
      else    "#{number}th"
    end
  end
end
parameterize(string, sep = '-')

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

Examples

class Person
  def to_param
    "#{id}-#{name.parameterize}"
  end
end
@person = Person.find(1)
# => #<Person id: 1, name: "Donald E. Knuth">
<%= link_to(@person.name, person_path(@person)) %>
# => <a href="/person/1-donald-e-knuth">Donald E. Knuth</a>
# File activesupport/lib/active_support/inflector.rb, line 259
def parameterize(string, sep = '-')
  # remove malformed utf8 characters
  string = string.toutf8 unless string.is_utf8?
  # replace accented chars with ther ascii equivalents
  parameterized_string = transliterate(string)
  # Turn unwanted chars into the seperator
  parameterized_string.gsub!(/[^a-z0-9\-_]+/, sep)
  unless sep.blank?
    re_sep = Regexp.escape(sep)
    # No more than one of the separator in a row.
    parameterized_string.gsub!(/#{re_sep}{2,}/, sep)
    # Remove leading/trailing separator.
    parameterized_string.gsub!(/^#{re_sep}|#{re_sep}$/, '')
  end
  parameterized_string.downcase
end
pluralize(word)

Returns the plural form of the word in the string.

Examples:

"post".pluralize             # => "posts"
"octopus".pluralize          # => "octopi"
"sheep".pluralize            # => "sheep"
"words".pluralize            # => "words"
"CamelOctopus".pluralize     # => "CamelOctopi"
# File activesupport/lib/active_support/inflector.rb, line 138
def pluralize(word)
  result = word.to_s.dup
  if word.empty? || inflections.uncountables.include?(result.downcase)
    result
  else
    inflections.plurals.each { |(rule, replacement)| break if result.gsub!(rule, replacement) }
    result
  end
end
singularize(word)

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

Examples:

"posts".singularize            # => "post"
"octopi".singularize           # => "octopus"
"sheep".singluarize            # => "sheep"
"word".singularize             # => "word"
"CamelOctopi".singularize      # => "CamelOctopus"
# File activesupport/lib/active_support/inflector.rb, line 157
def singularize(word)
  result = word.to_s.dup
  if inflections.uncountables.any? { |inflection| result =~ /#{inflection}\Z/ }
    result
  else
    inflections.singulars.each { |(rule, replacement)| break if result.gsub!(rule, replacement) }
    result
  end
end
tableize(class_name)

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

Examples

"RawScaledScorer".tableize # => "raw_scaled_scorers"
"egg_and_ham".tableize     # => "egg_and_hams"
"fancyCategory".tableize   # => "fancy_categories"
# File activesupport/lib/active_support/inflector.rb, line 306
def tableize(class_name)
  pluralize(underscore(class_name))
end
titleize(word)

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

titleizeis also aliased as as titlecase.

Examples:

"man from the boondocks".titleize # => "Man From The Boondocks"
"x-men: the last stand".titleize  # => "X Men: The Last Stand"
# File activesupport/lib/active_support/inflector.rb, line 195
def titleize(word)
  humanize(underscore(word)).gsub(/\b('?[a-z])/) { $1.capitalize }
end
transliterate(string)

Replaces accented characters with their ascii equivalents.

# File activesupport/lib/active_support/inflector.rb, line 278
def transliterate(string)
  Iconv.iconv('ascii//ignore//translit', 'utf-8', string).to_s
end
underscore(camel_cased_word)

The reverse of camelize. Makes an underscored, lowercase form from the expression in the string.

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

Examples:

"ActiveRecord".underscore         # => "active_record"
"ActiveRecord::Errors".underscore # => active_record/errors
# File activesupport/lib/active_support/inflector.rb, line 206
def underscore(camel_cased_word)
  camel_cased_word.to_s.gsub(/::/, '/').
    gsub(/([A-Z]+)([A-Z][a-z])/,'\1_\2').
    gsub(/([a-z\d])([A-Z])/,'\1_\2').
    tr("-", "_").
    downcase
end