A singleton instance of this class is yielded by Inflector.inflections, which can then be used to specify additional inflection rules. Examples: 

  ActiveSupport::Inflector.inflections do |inflect|
    inflect.plural /^(ox)$/i, '\1\2en'
    inflect.singular /^(ox)en/i, '\1'

    inflect.irregular 'octopus', 'octopi'

    inflect.uncountable "equipment"
  end

New rules are added at the top. So in the example above, the irregular rule for octopus will now be the first of the pluralization and singularization rules that is runs. This guarantees that your rules run before any of the rules that may already have been loaded.

Methods
A
C
H
I
N
P
S
U
Attributes
[R] plurals
[R] singulars
[R] uncountables
[R] humans
[R] acronyms
[R] acronym_regex
Class Public methods
instance()

Source: show | on GitHub 

    # File activesupport/lib/active_support/inflector/inflections.rb, line 19
19:       def self.instance
20:         @__instance__ ||= new
21:       end
new()

Source: show | on GitHub 

    # File activesupport/lib/active_support/inflector/inflections.rb, line 25
25:       def initialize
26:         @plurals, @singulars, @uncountables, @humans, @acronyms, @acronym_regex = [], [], [], [], {}, /(?=a)b/
27:       end
Instance Public methods
acronym(word)

Specifies a new acronym. An acronym must be specified as it will appear in a camelized string. An underscore string that contains the acronym will retain the acronym when passed to `camelize`, `humanize`, or `titleize`. A camelized string that contains the acronym will maintain the acronym when titleized or humanized, and will convert the acronym into a non-delimited single lowercase word when passed to underscore.

Examples: 

  acronym 'HTML'
  titleize 'html' #=> 'HTML'
  camelize 'html' #=> 'HTML'
  underscore 'MyHTML' #=> 'my_html'

The acronym, however, must occur as a delimited unit and not be part of another word for conversions to recognize it: 

  acronym 'HTTP'
  camelize 'my_http_delimited' #=> 'MyHTTPDelimited'
  camelize 'https' #=> 'Https', not 'HTTPs'
  underscore 'HTTPS' #=> 'http_s', not 'https'

  acronym 'HTTPS'
  camelize 'https' #=> 'HTTPS'
  underscore 'HTTPS' #=> 'https'

Note: Acronyms that are passed to `pluralize` will no longer be recognized, since the acronym will not occur as a delimited unit in the pluralized result. To work around this, you must specify the pluralized form as an acronym as well: 

   acronym 'API'
   camelize(pluralize('api')) #=> 'Apis'

   acronym 'APIs'
   camelize(pluralize('api')) #=> 'APIs'

`acronym` may be used to specify any word that contains an acronym or otherwise needs to maintain a non-standard capitalization. The only restriction is that the word must begin with a capital letter.

Examples: 

  acronym 'RESTful'
  underscore 'RESTful' #=> 'restful'
  underscore 'RESTfulController' #=> 'restful_controller'
  titleize 'RESTfulController' #=> 'RESTful Controller'
  camelize 'restful' #=> 'RESTful'
  camelize 'restful_controller' #=> 'RESTfulController'

  acronym 'McDonald'
  underscore 'McDonald' #=> 'mcdonald'
  camelize 'mcdonald' #=> 'McDonald'

Source: show | on GitHub 

    # File activesupport/lib/active_support/inflector/inflections.rb, line 75
75:       def acronym(word)
76:         @acronyms[word.downcase] = word
77:         @acronym_regex = /#{@acronyms.values.join("|")}/
78:       end
clear(scope = :all)

Clears the loaded inflections within a given scope (default is :all). Give the scope as a symbol of the inflection type, the options are: :plurals, :singulars, :uncountables, :humans.

Examples: 

  clear :all
  clear :plurals

Source: show | on GitHub 

     # File activesupport/lib/active_support/inflector/inflections.rb, line 147
147:       def clear(scope = :all)
148:         case scope
149:           when :all
150:             @plurals, @singulars, @uncountables, @humans = [], [], [], []
151:           else
152:             instance_variable_set "@#{scope}", []
153:         end
154:       end
human(rule, replacement)

Specifies a humanized form of a string by a regular expression rule or by a string mapping. When using a regular expression based replacement, the normal humanize formatting is called after the replacement. When a string is used, the human form should be specified as desired (example: ‘The name’, not ‘the_name’)

Examples: 

  human /_cnt$/i, '\1_count'
  human "legacy_col_person_name", "Name"

Source: show | on GitHub 

     # File activesupport/lib/active_support/inflector/inflections.rb, line 136
136:       def human(rule, replacement)
137:         @humans.insert(0, [rule, replacement])
138:       end
irregular(singular, plural)

Specifies a new irregular that applies to both pluralization and singularization at the same time. This can only be used for strings, not regular expressions. You simply pass the irregular in singular and plural form.

Examples: 

  irregular 'octopus', 'octopi'
  irregular 'person', 'people'

Source: show | on GitHub 

     # File activesupport/lib/active_support/inflector/inflections.rb, line 102
102:       def irregular(singular, plural)
103:         @uncountables.delete(singular)
104:         @uncountables.delete(plural)
105:         if singular[0,1].upcase == plural[0,1].upcase
106:           plural(Regexp.new("(#{singular[0,1]})#{singular[1..-1]}$", "i"), '\1' + plural[1..-1])
107:           plural(Regexp.new("(#{plural[0,1]})#{plural[1..-1]}$", "i"), '\1' + plural[1..-1])
108:           singular(Regexp.new("(#{plural[0,1]})#{plural[1..-1]}$", "i"), '\1' + singular[1..-1])
109:         else
110:           plural(Regexp.new("#{singular[0,1].upcase}(?i)#{singular[1..-1]}$"), plural[0,1].upcase + plural[1..-1])
111:           plural(Regexp.new("#{singular[0,1].downcase}(?i)#{singular[1..-1]}$"), plural[0,1].downcase + plural[1..-1])
112:           plural(Regexp.new("#{plural[0,1].upcase}(?i)#{plural[1..-1]}$"), plural[0,1].upcase + plural[1..-1])
113:           plural(Regexp.new("#{plural[0,1].downcase}(?i)#{plural[1..-1]}$"), plural[0,1].downcase + plural[1..-1])
114:           singular(Regexp.new("#{plural[0,1].upcase}(?i)#{plural[1..-1]}$"), singular[0,1].upcase + singular[1..-1])
115:           singular(Regexp.new("#{plural[0,1].downcase}(?i)#{plural[1..-1]}$"), singular[0,1].downcase + singular[1..-1])
116:         end
117:       end
plural(rule, replacement)

Specifies a new pluralization rule and its replacement. The rule can either be a string or a regular expression. The replacement should always be a string that may include references to the matched data from the rule.

Source: show | on GitHub 

    # File activesupport/lib/active_support/inflector/inflections.rb, line 82
82:       def plural(rule, replacement)
83:         @uncountables.delete(rule) if rule.is_a?(String)
84:         @uncountables.delete(replacement)
85:         @plurals.insert(0, [rule, replacement])
86:       end
singular(rule, replacement)

Specifies a new singularization rule and its replacement. The rule can either be a string or a regular expression. The replacement should always be a string that may include references to the matched data from the rule.

Source: show | on GitHub 

    # File activesupport/lib/active_support/inflector/inflections.rb, line 90
90:       def singular(rule, replacement)
91:         @uncountables.delete(rule) if rule.is_a?(String)
92:         @uncountables.delete(replacement)
93:         @singulars.insert(0, [rule, replacement])
94:       end
uncountable(*words)

Add uncountable words that shouldn’t be attempted inflected.

Examples: 

  uncountable "money"
  uncountable "money", "information"
  uncountable %w( money information rice )

Source: show | on GitHub 

     # File activesupport/lib/active_support/inflector/inflections.rb, line 125
125:       def uncountable(*words)
126:         (@uncountables << words).flatten!
127:       end