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ActiveSupport::Inflector

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).

Public Instance Methods

camelize(term, uppercase_first_letter = true) click to toggle source

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_model".camelize                # => "ActiveModel"
  "active_model".camelize(:lower)        # => "activeModel"
  "active_model/errors".camelize         # => "ActiveModel::Errors"
  "active_model/errors".camelize(:lower) # => "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:

  "SSLError".underscore.camelize # => "SslError"
    # File lib/active_support/inflector/methods.rb, line 55
55:     def camelize(term, uppercase_first_letter = true)
56:       string = term.to_s
57:       if uppercase_first_letter
58:         string = string.sub(/^[a-z\d]*/) { inflections.acronyms[$&] || $&.capitalize }
59:       else
60:         string = string.sub(/^(?:#{inflections.acronym_regex}(?=\b|[A-Z_])|\w)/) { $&.downcase }
61:       end
62:       string.gsub(/(?:_|(\/))([a-z\d]*)/) { "#{$1}#{inflections.acronyms[$2] || $2.capitalize}" }.gsub('/', '::')
63:     end
classify(table_name) click to toggle source

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"
     # File lib/active_support/inflector/methods.rb, line 140
140:     def classify(table_name)
141:       # strip out any leading schema name
142:       camelize(singularize(table_name.to_s.sub(/.*\./, '')))
143:     end
constantize(camel_cased_word) click to toggle source

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 lib/active_support/inflector/methods.rb, line 213
213:       def constantize(camel_cased_word)
214:         names = camel_cased_word.split('::')
215:         names.shift if names.empty? || names.first.empty?
216: 
217:         constant = Object
218:         names.each do |name|
219:           constant = constant.const_defined?(name) ? constant.const_get(name) : constant.const_missing(name)
220:         end
221:         constant
222:       end
dasherize(underscored_word) click to toggle source

Replaces underscores with dashes in the string.

Example:

  "puni_puni" # => "puni-puni"
     # File lib/active_support/inflector/methods.rb, line 149
149:     def dasherize(underscored_word)
150:       underscored_word.gsub(/_/, '-')
151:     end
deconstantize(path) click to toggle source

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

  "Net::HTTP".deconstantize   # => "Net"
  "::Net::HTTP".deconstantize # => "::Net"
  "String".deconstantize      # => ""
  "::String".deconstantize    # => ""
  "".deconstantize            # => ""

See also demodulize.

     # File lib/active_support/inflector/methods.rb, line 177
177:     def deconstantize(path)
178:       path.to_s[0...(path.rindex('::') || 0)] # implementation based on the one in facets' Module#spacename
179:     end
demodulize(path) click to toggle source

Removes the module part from the expression in the string:

  "ActiveRecord::CoreExtensions::String::Inflections".demodulize # => "Inflections"
  "Inflections".demodulize                                       # => "Inflections"

See also deconstantize.

     # File lib/active_support/inflector/methods.rb, line 159
159:     def demodulize(path)
160:       path = path.to_s
161:       if i = path.rindex('::')
162:         path[(i+2)..1]
163:       else
164:         path
165:       end
166:     end
foreign_key(class_name, separate_class_name_and_id_with_underscore = true) click to toggle source

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"
     # File lib/active_support/inflector/methods.rb, line 189
189:     def foreign_key(class_name, separate_class_name_and_id_with_underscore = true)
190:       underscore(demodulize(class_name)) + (separate_class_name_and_id_with_underscore ? "_id" : "id")
191:     end
humanize(lower_case_and_underscored_word) click to toggle source

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 lib/active_support/inflector/methods.rb, line 94
 94:     def humanize(lower_case_and_underscored_word)
 95:       result = lower_case_and_underscored_word.to_s.dup
 96:       inflections.humans.each { |(rule, replacement)| break if result.gsub!(rule, replacement) }
 97:       result.gsub!(/_id$/, "")
 98:       result.gsub!(/_/, ' ')
 99:       result.gsub(/([a-z\d]*)/) { |match|
100:         "#{inflections.acronyms[match] || match.downcase}"
101:       }.gsub(/^\w/) { $&.upcase }
102:     end
inflections() click to toggle source

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 lib/active_support/inflector/inflections.rb, line 166
166:     def inflections
167:       if block_given?
168:         yield Inflections.instance
169:       else
170:         Inflections.instance
171:       end
172:     end
ordinalize(number) click to toggle source

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"
  ordinalize(-11)   # => "-11th"
  ordinalize(-1021) # => "-1021st"
     # File lib/active_support/inflector/methods.rb, line 279
279:     def ordinalize(number)
280:       if (11..13).include?(number.to_i.abs % 100)
281:         "#{number}th"
282:       else
283:         case number.to_i.abs % 10
284:           when 1; "#{number}st"
285:           when 2; "#{number}nd"
286:           when 3; "#{number}rd"
287:           else    "#{number}th"
288:         end
289:       end
290:     end
parameterize(string, sep = '-') click to toggle source

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 lib/active_support/inflector/transliterate.rb, line 82
82:     def parameterize(string, sep = '-')
83:       # replace accented chars with their ascii equivalents
84:       parameterized_string = transliterate(string)
85:       # Turn unwanted chars into the separator
86:       parameterized_string.gsub!(/[^a-z0-9\-_]+/, sep)
87:       unless sep.nil? || sep.empty?
88:         re_sep = Regexp.escape(sep)
89:         # No more than one of the separator in a row.
90:         parameterized_string.gsub!(/#{re_sep}{2,}/, sep)
91:         # Remove leading/trailing separator.
92:         parameterized_string.gsub!(/^#{re_sep}|#{re_sep}$/, '')
93:       end
94:       parameterized_string.downcase
95:     end
pluralize(word) click to toggle source

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 lib/active_support/inflector/methods.rb, line 24
24:     def pluralize(word)
25:       apply_inflections(word, inflections.plurals)
26:     end
safe_constantize(camel_cased_word) click to toggle source

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

  "Module".safe_constantize     # => Module
  "Test::Unit".safe_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".safe_constantize # => 'outside', same as ::C
  end

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

  "blargle".safe_constantize  # => nil
  "UnknownModule".safe_constantize  # => nil
  "UnknownModule::Foo::Bar".safe_constantize  # => nil
     # File lib/active_support/inflector/methods.rb, line 258
258:     def safe_constantize(camel_cased_word)
259:       begin
260:         constantize(camel_cased_word)
261:       rescue NameError => e
262:         raise unless e.message =~ /(uninitialized constant|wrong constant name) #{const_regexp(camel_cased_word)}$/ ||
263:           e.name.to_s == camel_cased_word.to_s
264:       rescue ArgumentError => e
265:         raise unless e.message =~ /not missing constant #{const_regexp(camel_cased_word)}\!$/
266:       end
267:     end
singularize(word) click to toggle source

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

Examples:

  "posts".singularize            # => "post"
  "octopi".singularize           # => "octopus"
  "sheep".singularize            # => "sheep"
  "word".singularize             # => "word"
  "CamelOctopi".singularize      # => "CamelOctopus"
    # File lib/active_support/inflector/methods.rb, line 36
36:     def singularize(word)
37:       apply_inflections(word, inflections.singulars)
38:     end
tableize(class_name) click to toggle source

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"
     # File lib/active_support/inflector/methods.rb, line 126
126:     def tableize(class_name)
127:       pluralize(underscore(class_name))
128:     end
titleize(word) click to toggle source

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"
  "TheManWithoutAPast".titleize       # => "The Man Without A Past"
  "raiders_of_the_lost_ark".titleize  # => "Raiders Of The Lost Ark"
     # File lib/active_support/inflector/methods.rb, line 115
115:     def titleize(word)
116:       humanize(underscore(word)).gsub(/\b('?[a-z])/) { $1.capitalize }
117:     end
transliterate(string, replacement = "?") click to toggle source

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 => lambda {|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 lib/active_support/inflector/transliterate.rb, line 61
61:     def transliterate(string, replacement = "?")
62:       I18n.transliterate(ActiveSupport::Multibyte::Unicode.normalize(
63:         ActiveSupport::Multibyte::Unicode.tidy_bytes(string), :c),
64:           :replacement => replacement)
65:     end
underscore(camel_cased_word) click to toggle source

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

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

Examples:

  "ActiveModel".underscore         # => "active_model"
  "ActiveModel::Errors".underscore # => "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:

  "SSLError".underscore.camelize # => "SslError"
    # File lib/active_support/inflector/methods.rb, line 77
77:     def underscore(camel_cased_word)
78:       word = camel_cased_word.to_s.dup
79:       word.gsub!(/::/, '/')
80:       word.gsub!(/(?:([A-Za-z\d])|^)(#{inflections.acronym_regex})(?=\b|[^a-z])/) { "#{$1}#{$1 && '_'}#{$2.downcase}" }
81:       word.gsub!(/([A-Z\d]+)([A-Z][a-z])/,'\1_\2')
82:       word.gsub!(/([a-z\d])([A-Z])/,'\1_\2')
83:       word.tr!("-", "_")
84:       word.downcase!
85:       word
86:     end

Private Instance Methods

apply_inflections(word, rules) click to toggle source

Applies inflection rules for singularize and pluralize.

Examples:

 apply_inflections("post", inflections.plurals) # => "posts"
 apply_inflections("posts", inflections.singulars) # => "post"
     # File lib/active_support/inflector/methods.rb, line 310
310:     def apply_inflections(word, rules)
311:       result = word.to_s.dup
312: 
313:       if word.empty? || inflections.uncountables.any? { |inflection| result =~ /\b#{inflection}\Z/ }
314:         result
315:       else
316:         rules.each { |(rule, replacement)| break if result.gsub!(rule, replacement) }
317:         result
318:       end
319:     end

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