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 def camelize(term, uppercase_first_letter = true) string = term.to_s if uppercase_first_letter string = string.sub(/^[a-z\d]*/) { inflections.acronyms[$&] || $&.capitalize } else string = string.sub(/^(?:#{inflections.acronym_regex}(?=\b|[A-Z_])|\w)/) { $&.downcase } end string.gsub(/(?:_|(\/))([a-z\d]*)/) { "#{$1}#{inflections.acronyms[$2] || $2.capitalize}" }.gsub('/', '::') 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 def classify(table_name) # strip out any leading schema name camelize(singularize(table_name.to_s.sub(/.*\./, ''))) 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 def constantize(camel_cased_word) names = camel_cased_word.split('::') names.shift if names.empty? || names.first.empty? constant = Object names.each do |name| constant = constant.const_defined?(name) ? constant.const_get(name) : constant.const_missing(name) end constant end
Replaces underscores with dashes in the string.
Example:
"puni_puni" # => "puni-puni"
# File lib/active_support/inflector/methods.rb, line 149 def dasherize(underscored_word) underscored_word.gsub(/_/, '-') 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 def deconstantize(path) path.to_s[0...(path.rindex('::') || 0)] # implementation based on the one in facets' Module#spacename 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 def demodulize(path) path = path.to_s if i = path.rindex('::') path[(i+2)..-1] else path end 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 def foreign_key(class_name, separate_class_name_and_id_with_underscore = true) underscore(demodulize(class_name)) + (separate_class_name_and_id_with_underscore ? "_id" : "id") 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 def humanize(lower_case_and_underscored_word) result = lower_case_and_underscored_word.to_s.dup inflections.humans.each { |(rule, replacement)| break if result.gsub!(rule, replacement) } result.gsub!(/_id$/, "") result.gsub!(/_/, ' ') result.gsub(/([a-z\d]*)/) { |match| "#{inflections.acronyms[match] || match.downcase}" }.gsub(/^\w/) { $&.upcase } end
Yields a singleton instance of Inflector::Inflections so you can specify additional inflector rules.
Example:
ActiveSupport::Inflector.inflections do |inflect| inflect.uncountable "rails" end
# File lib/active_support/inflector/inflections.rb, line 166 def inflections if block_given? yield Inflections.instance else Inflections.instance end end
Turns a number into an ordinal string used to denote the position in an ordered sequence such as 1st, 2nd, 3rd, 4th.
Examples:
ordinalize(1) # => "1st" ordinalize(2) # => "2nd" ordinalize(1002) # => "1002nd" ordinalize(1003) # => "1003rd" ordinalize(-11) # => "-11th" ordinalize(-1021) # => "-1021st"
# File lib/active_support/inflector/methods.rb, line 279 def ordinalize(number) if (11..13).include?(number.to_i.abs % 100) "#{number}th" else case number.to_i.abs % 10 when 1; "#{number}st" when 2; "#{number}nd" when 3; "#{number}rd" else "#{number}th" end end end
Replaces special characters in a string so that it may be used as part of a 'pretty' URL.
class Person def to_param "#{id}-#{name.parameterize}" end end @person = Person.find(1) # => #<Person id: 1, name: "Donald E. Knuth"> <%= link_to(@person.name, person_path(@person)) %> # => <a href="/person/1-donald-e-knuth">Donald E. Knuth</a>
# File lib/active_support/inflector/transliterate.rb, line 81 def parameterize(string, sep = '-') # replace accented chars with their ascii equivalents parameterized_string = transliterate(string) # Turn unwanted chars into the separator parameterized_string.gsub!(/[^a-z0-9\-_]+/, sep) unless sep.nil? || sep.empty? re_sep = Regexp.escape(sep) # No more than one of the separator in a row. parameterized_string.gsub!(/#{re_sep}{2,}/, sep) # Remove leading/trailing separator. parameterized_string.gsub!(/^#{re_sep}|#{re_sep}$/, '') end parameterized_string.downcase 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 def pluralize(word) apply_inflections(word, inflections.plurals) 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 def safe_constantize(camel_cased_word) begin constantize(camel_cased_word) rescue NameError => e raise unless e.message =~ /(uninitialized constant|wrong constant name) #{const_regexp(camel_cased_word)}$/ || e.name.to_s == camel_cased_word.to_s rescue ArgumentError => e raise unless e.message =~ /not missing constant #{const_regexp(camel_cased_word)}\!$/ end 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 def singularize(word) apply_inflections(word, inflections.singulars) 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 def tableize(class_name) pluralize(underscore(class_name)) 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 def titleize(word) humanize(underscore(word)).gsub(/\b('?[a-z])/) { $1.capitalize } 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 def transliterate(string, replacement = "?") I18n.transliterate(ActiveSupport::Multibyte::Unicode.normalize( ActiveSupport::Multibyte::Unicode.tidy_bytes(string), :c), :replacement => replacement) 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 def underscore(camel_cased_word) word = camel_cased_word.to_s.dup word.gsub!(/::/, '/') word.gsub!(/(?:([A-Za-z\d])|^)(#{inflections.acronym_regex})(?=\b|[^a-z])/) { "#{$1}#{$1 && '_'}#{$2.downcase}" } word.gsub!(/([A-Z\d]+)([A-Z][a-z])/,'\1_\2') word.gsub!(/([a-z\d])([A-Z])/,'\1_\2') word.tr!("-", "_") word.downcase! word end