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).

Methods
Classes and Modules
Class ActiveSupport::Inflector::Inflections
Public Instance methods
camelize(lower_case_and_underscored_word, first_letter_in_uppercase = true)

By default, camelize converts strings to UpperCamelCase. If the argument to camelize is set to :lower then camelize produces lowerCamelCase.

camelize will 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"

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 179
179:     def camelize(lower_case_and_underscored_word, first_letter_in_uppercase = true)
180:       if first_letter_in_uppercase
181:         lower_case_and_underscored_word.to_s.gsub(/\/(.?)/) { "::#{$1.upcase}" }.gsub(/(?:^|_)(.)/) { $1.upcase }
182:       else
183:         lower_case_and_underscored_word.first.downcase + camelize(lower_case_and_underscored_word)[1..-1]
184:       end
185:     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 classify with constantize.)

Examples: 

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

Singular names are not handled correctly: 

  "business".classify     # => "Busines"

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 321
321:     def classify(table_name)
322:       # strip out any leading schema name
323:       camelize(singularize(table_name.to_s.sub(/.*\./, '')))
324:     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.

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 358
358:       def constantize(camel_cased_word)
359:         names = camel_cased_word.split('::')
360:         names.shift if names.empty? || names.first.empty?
361: 
362:         constant = Object
363:         names.each do |name|
364:           constant = constant.const_defined?(name) ? constant.const_get(name) : constant.const_missing(name)
365:         end
366:         constant
367:       end
dasherize(underscored_word)

Replaces underscores with dashes in the string.

Example: 

  "puni_puni" # => "puni-puni"

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 219
219:     def dasherize(underscored_word)
220:       underscored_word.gsub(/_/, '-')
221:     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"

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 241
241:     def demodulize(class_name_in_module)
242:       class_name_in_module.to_s.gsub(/^.*::/, '')
243:     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_underscore sets 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"

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 334
334:     def foreign_key(class_name, separate_class_name_and_id_with_underscore = true)
335:       underscore(demodulize(class_name)) + (separate_class_name_and_id_with_underscore ? "_id" : "id")
336:     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"

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 229
229:     def humanize(lower_case_and_underscored_word)
230:       result = lower_case_and_underscored_word.to_s.dup
231: 
232:       inflections.humans.each { |(rule, replacement)| break if result.gsub!(rule, replacement) }
233:       result.gsub(/_id$/, "").gsub(/_/, " ").capitalize
234:     end
inflections() {|Inflections.instance| ...}

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

Example: 

  ActiveSupport::Inflector.inflections do |inflect|
    inflect.uncountable "rails"
  end

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 123
123:     def inflections
124:       if block_given?
125:         yield Inflections.instance
126:       else
127:         Inflections.instance
128:       end
129:     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"

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 389
389:     def ordinalize(number)
390:       if (11..13).include?(number.to_i % 100)
391:         "#{number}th"
392:       else
393:         case number.to_i % 10
394:           when 1; "#{number}st"
395:           when 2; "#{number}nd"
396:           when 3; "#{number}rd"
397:           else    "#{number}th"
398:         end
399:       end
400:     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>

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 260
260:     def parameterize(string, sep = '-')
261:       # remove malformed utf8 characters
262:       string = string.toutf8 unless string.is_utf8?
263:       # replace accented chars with ther ascii equivalents
264:       parameterized_string = transliterate(string)
265:       # Turn unwanted chars into the seperator
266:       parameterized_string.gsub!(/[^a-z0-9\-_]+/i, sep)
267:       unless sep.blank?
268:         re_sep = Regexp.escape(sep)
269:         # No more than one of the separator in a row.
270:         parameterized_string.gsub!(/#{re_sep}{2,}/, sep)
271:         # Remove leading/trailing separator.
272:         parameterized_string.gsub!(/^#{re_sep}|#{re_sep}$/i, '')
273:       end
274:       parameterized_string.downcase
275:     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"

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 139
139:     def pluralize(word)
140:       result = word.to_s.dup
141: 
142:       if word.empty? || inflections.uncountables.include?(result.downcase)
143:         result
144:       else
145:         inflections.plurals.each { |(rule, replacement)| break if result.gsub!(rule, replacement) }
146:         result
147:       end
148:     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"

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 158
158:     def singularize(word)
159:       result = word.to_s.dup
160: 
161:       if inflections.uncountables.any? { |inflection| result =~ /#{inflection}\Z/i }
162:         result
163:       else
164:         inflections.singulars.each { |(rule, replacement)| break if result.gsub!(rule, replacement) }
165:         result
166:       end
167:     end
tableize(class_name)

Create 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.

Examples 

  "RawScaledScorer".tableize # => "raw_scaled_scorers"
  "egg_and_ham".tableize     # => "egg_and_hams"
  "fancyCategory".tableize   # => "fancy_categories"

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 307
307:     def tableize(class_name)
308:       pluralize(underscore(class_name))
309:     end
titleize(word)

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 as titlecase.

Examples: 

  "man from the boondocks".titleize # => "Man From The Boondocks"
  "x-men: the last stand".titleize  # => "X Men: The Last Stand"

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 196
196:     def titleize(word)
197:       humanize(underscore(word)).gsub(/\b('?[a-z])/) { $1.capitalize }
198:     end
transliterate(string)

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 294
294:       def transliterate(string)
295:         string.mb_chars.normalize(:kd). # Decompose accented characters
296:           gsub(/[^\x00-\x7F]+/, '')     # Remove anything non-ASCII entirely (e.g. diacritics).
297:       end
transliterate(string)

Replaces accented characters with their ascii equivalents.

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 279
279:     def transliterate(string)
280:       Iconv.iconv('ascii//ignore//translit', 'utf-8', string).to_s
281:     end
transliterate(string)

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 285
285:       def transliterate(string)
286:         warn "Ruby 1.9 doesn't support Unicode normalization yet"
287:         string.dup
288:       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

[ show source ]

     # File activesupport/lib/active_support/inflector.rb, line 207
207:     def underscore(camel_cased_word)
208:       camel_cased_word.to_s.gsub(/::/, '/').
209:         gsub(/([A-Z]+)([A-Z][a-z])/,'\1_\2').
210:         gsub(/([a-z\d])([A-Z])/,'\1_\2').
211:         tr("-", "_").
212:         downcase
213:     end