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 or wish to define rules for languages other than English, please correct or add them yourself (explained below).
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Constants
ALLOWED_ENCODINGS_FOR_TRANSLITERATE | = | [Encoding::UTF_8, Encoding::US_ASCII, Encoding::GB18030].freeze |
Instance Public methods
camelize(term, uppercase_first_letter = true) Link
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 69 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.acronyms_camelize_regex) { |match| match.downcase } end string.gsub!(/(?:_|(\/))([a-z\d]*)/i) { "#{$1}#{inflections.acronyms[$2] || $2.capitalize}" } string.gsub!("/", "::") string end
classify(table_name) Link
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') # => "Calculu"
constantize(camel_cased_word) Link
Tries to find a constant with the name specified in the argument string.
constantize('Module') # => Module
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'
constantize('C') # => '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 271 def constantize(camel_cased_word) if camel_cased_word.blank? || !camel_cased_word.include?("::") Object.const_get(camel_cased_word) else names = camel_cased_word.split("::") # 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 end
dasherize(underscored_word) Link
Replaces underscores with dashes in the string.
dasherize('puni_puni') # => "puni-puni"
deconstantize(path) Link
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
.
demodulize(path) Link
Removes the module part from the expression in the string.
demodulize('ActiveSupport::Inflector::Inflections') # => "Inflections"
demodulize('Inflections') # => "Inflections"
demodulize('::Inflections') # => "Inflections"
demodulize('') # => ""
See also deconstantize
.
foreign_key(class_name, separate_class_name_and_id_with_underscore = true) Link
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"
humanize(lower_case_and_underscored_word, capitalize: true, keep_id_suffix: false) Link
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).
The trailing '_id' can be kept and capitalized by setting the optional parameter keep_id_suffix
to true (default is false).
humanize('employee_salary') # => "Employee salary"
humanize('author_id') # => "Author"
humanize('author_id', capitalize: false) # => "author"
humanize('_id') # => "Id"
humanize('author_id', keep_id_suffix: true) # => "Author Id"
If “SSL” was defined to be an acronym:
humanize('ssl_error') # => "SSL error"
# File activesupport/lib/active_support/inflector/methods.rb, line 128 def humanize(lower_case_and_underscored_word, capitalize: true, keep_id_suffix: false) result = lower_case_and_underscored_word.to_s.dup inflections.humans.each { |(rule, replacement)| break if result.sub!(rule, replacement) } result.sub!(/\A_+/, "") unless keep_id_suffix result.delete_suffix!("_id") end result.tr!("_", " ") result.gsub!(/([a-z\d]*)/i) do |match| "#{inflections.acronyms[match.downcase] || match.downcase}" end if capitalize result.sub!(/\A\w/) { |match| match.upcase } end result end
inflections(locale = :en) Link
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
ordinal(number) Link
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"
ordinalize(number) Link
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"
parameterize(string, separator: "-", preserve_case: false, locale: nil) Link
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("^très|Jolie-- ") # => "tres-jolie"
To use a custom separator, override the separator
argument.
parameterize("Donald E. Knuth", separator: '_') # => "donald_e_knuth"
parameterize("^très|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("^très|Jolie-- ", preserve_case: true) # => "tres-Jolie"
It preserves dashes and underscores unless they are used as separators:
parameterize("^très|Jolie__ ") # => "tres-jolie__"
parameterize("^très|Jolie-- ", separator: "_") # => "tres_jolie--"
parameterize("^très_Jolie-- ", separator: ".") # => "tres_jolie--"
If the optional parameter locale
is specified, the word will be parameterized as a word of that language. By default, this parameter is set to nil
and it will use the configured I18n.locale
.
# File activesupport/lib/active_support/inflector/transliterate.rb, line 121 def parameterize(string, separator: "-", preserve_case: false, locale: nil) # Replace accented chars with their ASCII equivalents. parameterized_string = transliterate(string, locale: locale) # Turn unwanted chars into the separator. parameterized_string.gsub!(/[^a-z0-9\-_]+/i, separator) unless separator.nil? || separator.empty? if separator == "-" 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, "") end parameterized_string.downcase! unless preserve_case parameterized_string end
pluralize(word, locale = :en) Link
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"
safe_constantize(camel_cased_word) Link
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 328 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 LoadError => e message = e.respond_to?(:original_message) ? e.original_message : e.message raise unless /Unable to autoload constant #{const_regexp(camel_cased_word)}/.match?(message) end
singularize(word, locale = :en) Link
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"
tableize(class_name) Link
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"
titleize(word, keep_id_suffix: false) Link
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.
The trailing '_id','Id'.. can be kept and capitalized by setting the optional parameter keep_id_suffix
to true. By default, this parameter is false.
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"
titleize('string_ending_with_id', keep_id_suffix: true) # => "String Ending With Id"
transliterate(string, replacement = "?", locale: nil) Link
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:
transliterate('Jürgen', locale: :en)
# => "Jurgen"
transliterate('Jürgen', locale: :de)
# => "Juergen"
Transliteration is restricted to UTF-8, US-ASCII and GB18030 strings Other encodings will raise an ArgumentError.
# File activesupport/lib/active_support/inflector/transliterate.rb, line 64 def transliterate(string, replacement = "?", locale: nil) string = string.dup if string.frozen? raise ArgumentError, "Can only transliterate strings. Received #{string.class.name}" unless string.is_a?(String) raise ArgumentError, "Cannot transliterate strings with #{string.encoding} encoding" unless ALLOWED_ENCODINGS_FOR_TRANSLITERATE.include?(string.encoding) input_encoding = string.encoding # US-ASCII is a subset of UTF-8 so we'll force encoding as UTF-8 if # US-ASCII is given. This way we can let tidy_bytes handle the string # in the same way as we do for UTF-8 string.force_encoding(Encoding::UTF_8) if string.encoding == Encoding::US_ASCII # GB18030 is Unicode compatible but is not a direct mapping so needs to be # transcoded. Using invalid/undef :replace will result in loss of data in # the event of invalid characters, but since tidy_bytes will replace # invalid/undef with a "?" we're safe to do the same beforehand string.encode!(Encoding::UTF_8, invalid: :replace, undef: :replace) if string.encoding == Encoding::GB18030 transliterated = I18n.transliterate( ActiveSupport::Multibyte::Unicode.tidy_bytes(string).unicode_normalize(:nfc), replacement: replacement, locale: locale ) # Restore the string encoding of the input if it was not UTF-8. # Apply invalid/undef :replace as tidy_bytes does transliterated.encode!(input_encoding, invalid: :replace, undef: :replace) if input_encoding != transliterated.encoding transliterated end
underscore(camel_cased_word) Link
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 92 def underscore(camel_cased_word) return camel_cased_word unless /[A-Z-]|::/.match?(camel_cased_word) word = camel_cased_word.to_s.gsub("::", "/") word.gsub!(inflections.acronyms_underscore_regex) { "#{$1 && '_' }#{$2.downcase}" } word.gsub!(/([A-Z])(?=[A-Z][a-z])|([a-z\d])(?=[A-Z])/) { ($1 || $2) << "_" } word.tr!("-", "_") word.downcase! word end
upcase_first(string) Link
Converts just the first character to uppercase.
upcase_first('what a Lovely Day') # => "What a Lovely Day"
upcase_first('w') # => "W"
upcase_first('') # => ""