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).
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
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
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
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
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
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
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
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/) { $&.upcase } 102: end
Yields a singleton instance of Inflector::Inflections so you can specify additional inflector rules.
Example:
ActiveSupport::Inflector.inflections do |inflect| inflect.uncountable "rails" end
# File lib/active_support/inflector/inflections.rb, line 166 166: def inflections 167: if block_given? 168: yield Inflections.instance 169: else 170: Inflections.instance 171: end 172: end
Turns a number into an ordinal string used to denote the position in an ordered sequence such as 1st, 2nd, 3rd, 4th.
Examples:
ordinalize(1) # => "1st" ordinalize(2) # => "2nd" ordinalize(1002) # => "1002nd" ordinalize(1003) # => "1003rd" ordinalize(-11) # => "-11th" ordinalize(-1021) # => "-1021st"
# File lib/active_support/inflector/methods.rb, line 279 279: def ordinalize(number) 280: if (11..13).include?(number.to_i.abs % 100) 281: "#{number}th" 282: else 283: case number.to_i.abs % 10 284: when 1; "#{number}st" 285: when 2; "#{number}nd" 286: when 3; "#{number}rd" 287: else "#{number}th" 288: end 289: end 290: end
Replaces special characters in a string so that it may be used as part of a ‘pretty’ URL.
class Person def to_param "#{id}-#{name.parameterize}" end end @person = Person.find(1) # => #<Person id: 1, name: "Donald E. Knuth"> <%= link_to(@person.name, person_path(@person)) %> # => <a href="/person/1-donald-e-knuth">Donald E. Knuth</a>
# File lib/active_support/inflector/transliterate.rb, line 82 82: def parameterize(string, sep = '-') 83: # replace accented chars with their ascii equivalents 84: parameterized_string = transliterate(string) 85: # Turn unwanted chars into the separator 86: parameterized_string.gsub!(/[^a-z0-9\-_]+/, sep) 87: unless sep.nil? || sep.empty? 88: re_sep = Regexp.escape(sep) 89: # No more than one of the separator in a row. 90: parameterized_string.gsub!(/#{re_sep}{2,}/, sep) 91: # Remove leading/trailing separator. 92: parameterized_string.gsub!(/^#{re_sep}|#{re_sep}$/, '') 93: end 94: parameterized_string.downcase 95: end
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
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
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
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
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
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
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
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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