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_record".camelize # => "ActiveRecord" "active_record".camelize(:lower) # => "activeRecord" "active_record/errors".camelize # => "ActiveRecord::Errors" "active_record/errors".camelize(:lower) # => "activeRecord::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 28 28: def camelize(lower_case_and_underscored_word, first_letter_in_uppercase = true) 29: if first_letter_in_uppercase 30: lower_case_and_underscored_word.to_s.gsub(/\/(.?)/) { "::#{$1.upcase}" }.gsub(/(?:^|_)(.)/) { $1.upcase } 31: else 32: lower_case_and_underscored_word.to_s[0].chr.downcase + camelize(lower_case_and_underscored_word)[1..1] 33: end 34: 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/inflections.rb, line 206 206: def classify(table_name) 207: # strip out any leading schema name 208: camelize(singularize(table_name.to_s.sub(/.*\./, ''))) 209: 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 107 107: def constantize(camel_cased_word) 108: names = camel_cased_word.split('::') 109: names.shift if names.empty? || names.first.empty? 110: 111: constant = Object 112: names.each do |name| 113: constant = constant.const_defined?(name) ? constant.const_get(name) : constant.const_missing(name) 114: end 115: constant 116: end
Replaces underscores with dashes in the string.
Example:
"puni_puni" # => "puni-puni"
# File lib/active_support/inflector/methods.rb, line 62 62: def dasherize(underscored_word) 63: underscored_word.gsub(/_/, '-') 64: end
Removes the module part from the expression in the string.
Examples:
"ActiveRecord::CoreExtensions::String::Inflections".demodulize # => "Inflections" "Inflections".demodulize # => "Inflections"
# File lib/active_support/inflector/methods.rb, line 71 71: def demodulize(class_name_in_module) 72: class_name_in_module.to_s.gsub(/^.*::/, '') 73: 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 83 83: def foreign_key(class_name, separate_class_name_and_id_with_underscore = true) 84: underscore(demodulize(class_name)) + (separate_class_name_and_id_with_underscore ? "_id" : "id") 85: 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/inflections.rb, line 165 165: def humanize(lower_case_and_underscored_word) 166: result = lower_case_and_underscored_word.to_s.dup 167: 168: inflections.humans.each { |(rule, replacement)| break if result.gsub!(rule, replacement) } 169: result.gsub(/_id$/, "").gsub(/_/, " ").capitalize 170: 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 113 113: def inflections 114: if block_given? 115: yield Inflections.instance 116: else 117: Inflections.instance 118: end 119: 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"
# File lib/active_support/inflector/methods.rb, line 138 138: def ordinalize(number) 139: if (11..13).include?(number.to_i % 100) 140: "#{number}th" 141: else 142: case number.to_i % 10 143: when 1; "#{number}st" 144: when 2; "#{number}nd" 145: when 3; "#{number}rd" 146: else "#{number}th" 147: end 148: end 149: 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 81 81: def parameterize(string, sep = '-') 82: # replace accented chars with their ascii equivalents 83: parameterized_string = transliterate(string) 84: # Turn unwanted chars into the separator 85: parameterized_string.gsub!(/[^a-z0-9\-_]+/, sep) 86: unless sep.nil? || sep.empty? 87: re_sep = Regexp.escape(sep) 88: # No more than one of the separator in a row. 89: parameterized_string.gsub!(/#{re_sep}{2,}/, sep) 90: # Remove leading/trailing separator. 91: parameterized_string.gsub!(/^#{re_sep}|#{re_sep}$/, '') 92: end 93: parameterized_string.downcase 94: 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/inflections.rb, line 129 129: def pluralize(word) 130: result = word.to_s.dup 131: 132: if word.empty? || inflections.uncountables.include?(result.downcase) 133: result 134: else 135: inflections.plurals.each { |(rule, replacement)| break if result.gsub!(rule, replacement) } 136: result 137: end 138: 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/inflections.rb, line 148 148: def singularize(word) 149: result = word.to_s.dup 150: 151: if inflections.uncountables.any? { |inflection| result =~ /#{inflection}\Z/ } 152: result 153: else 154: inflections.singulars.each { |(rule, replacement)| break if result.gsub!(rule, replacement) } 155: result 156: end 157: 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/inflections.rb, line 192 192: def tableize(class_name) 193: pluralize(underscore(class_name)) 194: 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"
# File lib/active_support/inflector/inflections.rb, line 181 181: def titleize(word) 182: humanize(underscore(word)).gsub(/\b('?[a-z])/) { $1.capitalize } 183: 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 60 60: def transliterate(string, replacement = "?") 61: I18n.transliterate(ActiveSupport::Multibyte::Unicode.normalize( 62: ActiveSupport::Multibyte::Unicode.tidy_bytes(string), :c), 63: :replacement => replacement) 64: end
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
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 48 48: def underscore(camel_cased_word) 49: word = camel_cased_word.to_s.dup 50: word.gsub!(/::/, '/') 51: word.gsub!(/([A-Z]+)([A-Z][a-z])/,'\1_\2') 52: word.gsub!(/([a-z\d])([A-Z])/,'\1_\2') 53: word.tr!("-", "_") 54: word.downcase! 55: word 56: end
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