Module ActiveSupport::Inflector

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.

'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"

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).

'egg_and_hams'.classify # => "EggAndHam"
'posts'.classify        # => "Post"

Singular names are not handled correctly:

'calculus'.classify     # => "Calculu"

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.

Replaces underscores with dashes in the string.

'puni_puni'.dasherize # => "puni-puni"

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.

Removes the module part from the expression in the string.

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

See also deconstantize.

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'.

'Message'.foreign_key        # => "message_id"
'Message'.foreign_key(false) # => "messageid"
'Admin::Post'.foreign_key    # => "post_id"

Capitalizes the first word, turns underscores into spaces, and strips a trailing '_id' if present. Like titleize, this is meant for creating pretty output.

The capitalization of the first word can be turned off by setting the optional parameter capitalize to false. By default, this parameter is true.

humanize('employee_salary')              # => "Employee salary"
humanize('author_id')                    # => "Author"
humanize('author_id', capitalize: false) # => "author"

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

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"

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"

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>

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.

'post'.pluralize             # => "posts"
'octopus'.pluralize          # => "octopi"
'sheep'.pluralize            # => "sheep"
'words'.pluralize            # => "words"
'CamelOctopus'.pluralize     # => "CamelOctopi"
'ley'.pluralize(:es)         # => "leyes"

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

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.

'posts'.singularize            # => "post"
'octopi'.singularize           # => "octopus"
'sheep'.singularize            # => "sheep"
'word'.singularize             # => "word"
'CamelOctopi'.singularize      # => "CamelOctopus"
'leyes'.singularize(:es)       # => "ley"

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.

'RawScaledScorer'.tableize # => "raw_scaled_scorers"
'egg_and_ham'.tableize     # => "egg_and_hams"
'fancyCategory'.tableize   # => "fancy_categories"

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 titlecase.

'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"

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:

I18n.locale = :en
transliterate('Jürgen')
# => "Jurgen"

I18n.locale = :de
transliterate('Jürgen')
# => "Juergen"

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

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

'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"