String inflections define new methods on the String class to transform names for different purposes. For instance, you can figure out the name of a database from the name of a class.

"ScaleScore".tableize # => "scale_scores"
Methods
Public Instance methods
acts_like_string?()

Enable more predictable duck-typing on String-like classes. See Object#acts_like?.

  # File activesupport/lib/active_support/core_ext/string/behavior.rb, line 4
def acts_like_string?
  true
end
as_json(options = nil)
  # File activesupport/lib/active_support/json/encoding.rb, line 172
def as_json(options = nil) self end
at(position)

Returns the character at the position treating the string as an array (where 0 is the first character).

Examples:

"hello".at(0)  # => "h"
"hello".at(4)  # => "o"
"hello".at(10) # => ERROR if < 1.9, nil in 1.9
  # File activesupport/lib/active_support/core_ext/string/access.rb, line 11
def at(position)
  mb_chars[position, 1].to_s
end
camelize(first_letter = :upper)

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_record".camelize                # => "ActiveRecord"
"active_record".camelize(:lower)        # => "activeRecord"
"active_record/errors".camelize         # => "ActiveRecord::Errors"
"active_record/errors".camelize(:lower) # => "activeRecord::Errors"
This method is also aliased as camelcase
  # File activesupport/lib/active_support/core_ext/string/inflections.rb, line 55
def camelize(first_letter = :upper)
  case first_letter
    when :upper then ActiveSupport::Inflector.camelize(self, true)
    when :lower then ActiveSupport::Inflector.camelize(self, false)
  end
end
classify()

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.

"business".classify # => "Busines"
  # File activesupport/lib/active_support/core_ext/string/inflections.rb, line 140
def classify
  ActiveSupport::Inflector.classify(self)
end
constantize()

constantize tries to find a declared constant with the name specified in the string. It raises a NameError when the name is not in CamelCase or is not initialized.

Examples

"Module".constantize # => Module
"Class".constantize  # => Class
  # File activesupport/lib/active_support/core_ext/string/inflections.rb, line 42
def constantize
  ActiveSupport::Inflector.constantize(self)
end
dasherize()

Replaces underscores with dashes in the string.

"puni_puni" # => "puni-puni"
  # File activesupport/lib/active_support/core_ext/string/inflections.rb, line 89
def dasherize
  ActiveSupport::Inflector.dasherize(self)
end
demodulize()

Removes the module part from the constant expression in the string.

"ActiveRecord::CoreExtensions::String::Inflections".demodulize # => "Inflections"
"Inflections".demodulize                                       # => "Inflections"
  # File activesupport/lib/active_support/core_ext/string/inflections.rb, line 97
def demodulize
  ActiveSupport::Inflector.demodulize(self)
end
encode_json(encoder)
  # File activesupport/lib/active_support/json/encoding.rb, line 173
def encode_json(encoder) encoder.escape(self) end
encoding_aware?()
  # File activesupport/lib/active_support/core_ext/string/encoding.rb, line 3
def encoding_aware?
  true
end
exclude?(string)

The inverse of String#include?. Returns true if the string does not include the other string.

  # File activesupport/lib/active_support/core_ext/string/exclude.rb, line 3
def exclude?(string)
  !include?(string)
end
first(limit = 1)

Returns the first character of the string or the first limit characters.

Examples:

"hello".first     # => "h"
"hello".first(2)  # => "he"
"hello".first(10) # => "hello"
  # File activesupport/lib/active_support/core_ext/string/access.rb, line 41
def first(limit = 1)
  if limit == 0
    ''
  elsif limit >= size
    self
  else
    mb_chars[0...limit].to_s
  end
end
foreign_key(separate_class_name_and_id_with_underscore = true)

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 activesupport/lib/active_support/core_ext/string/inflections.rb, line 161
def foreign_key(separate_class_name_and_id_with_underscore = true)
  ActiveSupport::Inflector.foreign_key(self, separate_class_name_and_id_with_underscore)
end
from(position)

Returns the remaining of the string from the position treating the string as an array (where 0 is the first character).

Examples:

"hello".from(0)  # => "hello"
"hello".from(2)  # => "llo"
"hello".from(10) # => "" if < 1.9, nil in 1.9
  # File activesupport/lib/active_support/core_ext/string/access.rb, line 21
def from(position)
  mb_chars[position..-1].to_s
end
html_safe()
  # File activesupport/lib/active_support/core_ext/string/output_safety.rb, line 127
def html_safe
  ActiveSupport::SafeBuffer.new(self)
end
html_safe!()
  # File activesupport/lib/active_support/core_ext/string/output_safety.rb, line 123
def html_safe!
  raise "You can't call html_safe! on a String"
end
humanize()

Capitalizes the first word, turns underscores into spaces, and strips ‘_id’. Like titleize, this is meant for creating pretty output.

"employee_salary" # => "Employee salary"
"author_id"       # => "Author"
  # File activesupport/lib/active_support/core_ext/string/inflections.rb, line 149
def humanize
  ActiveSupport::Inflector.humanize(self)
end
is_utf8?()
  # File activesupport/lib/active_support/core_ext/string/multibyte.rb, line 46
def is_utf8? #:nodoc
  case encoding
  when Encoding::UTF_8
    valid_encoding?
  when Encoding::ASCII_8BIT, Encoding::US_ASCII
    dup.force_encoding(Encoding::UTF_8).valid_encoding?
  else
    false
  end
end
last(limit = 1)

Returns the last character of the string or the last limit characters.

Examples:

"hello".last     # => "o"
"hello".last(2)  # => "lo"
"hello".last(10) # => "hello"
  # File activesupport/lib/active_support/core_ext/string/access.rb, line 57
def last(limit = 1)
  if limit == 0
    ''
  elsif limit >= size
    self
  else
    mb_chars[(-limit)..-1].to_s
  end
end
mb_chars()

Multibyte proxy

mb_chars is a multibyte safe proxy for string methods.

In Ruby 1.8 and older it creates and returns an instance of the ActiveSupport::Multibyte::Chars class which encapsulates the original string. A Unicode safe version of all the String methods are defined on this proxy class. If the proxy class doesn’t respond to a certain method, it’s forwarded to the encapsuled string.

name = 'Claus Müller'
name.reverse # => "rell??M sualC"
name.length  # => 13

name.mb_chars.reverse.to_s # => "rellüM sualC"
name.mb_chars.length       # => 12

In Ruby 1.9 and newer mb_chars returns self because String is (mostly) encoding aware. This means that it becomes easy to run one version of your code on multiple Ruby versions.

Method chaining

All the methods on the Chars proxy which normally return a string will return a Chars object. This allows method chaining on the result of any of these methods.

name.mb_chars.reverse.length # => 12

Interoperability and configuration

The Chars object tries to be as interchangeable with String objects as possible: sorting and comparing between String and Char work like expected. The bang! methods change the internal string representation in the Chars object. Interoperability problems can be resolved easily with a to_s call.

For more information about the methods defined on the Chars proxy see ActiveSupport::Multibyte::Chars. For information about how to change the default Multibyte behaviour see ActiveSupport::Multibyte.

  # File activesupport/lib/active_support/core_ext/string/multibyte.rb, line 38
def mb_chars
  if ActiveSupport::Multibyte.proxy_class.consumes?(self)
    ActiveSupport::Multibyte.proxy_class.new(self)
  else
    self
  end
end
ord()

Returns the codepoint of the first character of the string, assuming a single-byte character encoding:

"a".ord # => 97
"à".ord # => 224, in ISO-8859-1

This method is defined in Ruby 1.8 for Ruby 1.9 forward compatibility on these character encodings.

ActiveSupport::Multibyte::Chars#ord is forward compatible with Ruby 1.9 on UTF8 strings:

"a".mb_chars.ord # => 97
"à".mb_chars.ord # => 224, in UTF8

Note that the 224 is different in both examples. In ISO-8859-1 “à” is represented as a single byte, 224. In UTF8 it is represented with two bytes, namely 195 and 160, but its Unicode codepoint is 224. If we call ord on the UTF8 string “à” the return value will be 195. That is not an error, because UTF8 is unsupported, the call itself would be bogus.

  # File activesupport/lib/active_support/core_ext/string/conversions.rb, line 27
def ord
  self[0]
end
parameterize(sep = '-')

Replaces special characters in a string so that it may be used as part of a ‘pretty’ URL.

Examples

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 %>
# => <a href="/person/1-donald-e-knuth">Donald E. Knuth</a>
  # File activesupport/lib/active_support/core_ext/string/inflections.rb, line 116
def parameterize(sep = '-')
  ActiveSupport::Inflector.parameterize(self, sep)
end
pluralize()

Returns the plural form of the word in the string.

"post".pluralize             # => "posts"
"octopus".pluralize          # => "octopi"
"sheep".pluralize            # => "sheep"
"words".pluralize            # => "words"
"the blue mailman".pluralize # => "the blue mailmen"
"CamelOctopus".pluralize     # => "CamelOctopi"
  # File activesupport/lib/active_support/core_ext/string/inflections.rb, line 19
def pluralize
  ActiveSupport::Inflector.pluralize(self)
end
singularize()

The reverse of pluralize, returns the singular form of a word in a string.

"posts".singularize            # => "post"
"octopi".singularize           # => "octopus"
"sheep".singularize            # => "sheep"
"word".singularize             # => "word"
"the blue mailmen".singularize # => "the blue mailman"
"CamelOctopi".singularize      # => "CamelOctopus"
  # File activesupport/lib/active_support/core_ext/string/inflections.rb, line 31
def singularize
  ActiveSupport::Inflector.singularize(self)
end
squish()

Returns the string, first removing all whitespace on both ends of the string, and then changing remaining consecutive whitespace groups into one space each.

Examples:

%{ Multi-line
   string }.squish                   # => "Multi-line string"
" foo   bar    \n   \t   boo".squish # => "foo bar boo"
  # File activesupport/lib/active_support/core_ext/string/filters.rb, line 12
def squish
  dup.squish!
end
squish!()

Performs a destructive squish. See String#squish.

  # File activesupport/lib/active_support/core_ext/string/filters.rb, line 17
def squish!
  strip!
  gsub!(/\s+/, ' ')
  self
end
strip_heredoc()

Strips indentation in heredocs.

For example in

if options[:usage]
  puts <<-USAGE.strip_heredoc
    This command does such and such.

    Supported options are:
      -h         This message
      ...
  USAGE
end

the user would see the usage message aligned against the left margin.

Technically, it looks for the least indented line in the whole string, and removes that amount of leading whitespace.

  # File activesupport/lib/active_support/core_ext/string/strip.rb, line 22
def strip_heredoc
  indent = scan(/^[ \t]*(?=\S)/).min.try(:size) || 0
  gsub(/^[ \t]{#{indent}}/, '')
end
tableize()

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.

"RawScaledScorer".tableize # => "raw_scaled_scorers"
"egg_and_ham".tableize     # => "egg_and_hams"
"fancyCategory".tableize   # => "fancy_categories"
  # File activesupport/lib/active_support/core_ext/string/inflections.rb, line 126
def tableize
  ActiveSupport::Inflector.tableize(self)
end
titleize()

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"
This method is also aliased as titlecase
  # File activesupport/lib/active_support/core_ext/string/inflections.rb, line 71
def titleize
  ActiveSupport::Inflector.titleize(self)
end
to(position)

Returns the beginning of the string up to the position treating the string as an array (where 0 is the first character).

Examples:

"hello".to(0)  # => "h"
"hello".to(2)  # => "hel"
"hello".to(10) # => "hello"
  # File activesupport/lib/active_support/core_ext/string/access.rb, line 31
def to(position)
  mb_chars[0..position].to_s
end
to_date()
  # File activesupport/lib/active_support/core_ext/string/conversions.rb, line 42
def to_date
  return nil if self.blank?
  ::Date.new(*::Date._parse(self, false).values_at(:year, :mon, :mday))
end
to_datetime()
  # File activesupport/lib/active_support/core_ext/string/conversions.rb, line 47
def to_datetime
  return nil if self.blank?
  d = ::Date._parse(self, false).values_at(:year, :mon, :mday, :hour, :min, :sec, :zone, :sec_fraction).map { |arg| arg || 0 }
  d[5] += d.pop
  ::DateTime.civil(*d)
end
to_time(form = :utc)

Form can be either :utc (default) or :local.

  # File activesupport/lib/active_support/core_ext/string/conversions.rb, line 35
def to_time(form = :utc)
  return nil if self.blank?
  d = ::Date._parse(self, false).values_at(:year, :mon, :mday, :hour, :min, :sec, :sec_fraction).map { |arg| arg || 0 }
  d[6] *= 1000000
  ::Time.send("#{form}_time", *d)
end
truncate(length, options = {})

Truncates a given text after a given length if text is longer than length:

"Once upon a time in a world far far away".truncate(27)
# => "Once upon a time in a wo..."

The last characters will be replaced with the :omission string (defaults to “…”) for a total length not exceeding :length:

"Once upon a time in a world far far away".truncate(27, :separator => ' ')
# => "Once upon a time in a..."

Pass a :separator to truncate text at a natural break:

"And they found that many people were sleeping better.".truncate(25, :omission => "... (continued)")
# => "And they f... (continued)"
  # File activesupport/lib/active_support/core_ext/string/filters.rb, line 38
def truncate(length, options = {})
  text = self.dup
  options[:omission] ||= "..."

  length_with_room_for_omission = length - options[:omission].mb_chars.length
  chars = text.mb_chars
  stop = options[:separator] ?
    (chars.rindex(options[:separator].mb_chars, length_with_room_for_omission) || length_with_room_for_omission) : length_with_room_for_omission

  (chars.length > length ? chars[0...stop] + options[:omission] : text).to_s
end
underscore()

The reverse of camelize. Makes an underscored, lowercase form from the expression in the string.

underscore will also change ‘::’ to ‘/’ to convert namespaces to paths.

"ActiveRecord".underscore         # => "active_record"
"ActiveRecord::Errors".underscore # => active_record/errors
  # File activesupport/lib/active_support/core_ext/string/inflections.rb, line 82
def underscore
  ActiveSupport::Inflector.underscore(self)
end