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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 table from the name of a class.

'ScaleScore'.tableize # => "scale_scores"
Methods
A
B
C
D
E
F
H
I
L
M
P
R
S
T
U
Constants
BLANK_RE = /\A[[:space:]]*\z/
 
Instance Public 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 3
def acts_like_string?
  true
end
at(position)

If you pass a single Fixnum, returns a substring of one character at that position. The first character of the string is at position 0, the next at position 1, and so on. If a range is supplied, a substring containing characters at offsets given by the range is returned. In both cases, if an offset is negative, it is counted from the end of the string. Returns nil if the initial offset falls outside the string. Returns an empty string if the beginning of the range is greater than the end of the string.

str = "hello"
str.at(0)      # => "h"
str.at(1..3)   # => "ell"
str.at(-2)     # => "l"
str.at(-2..-1) # => "lo"
str.at(5)      # => nil
str.at(5..-1)  # => ""

If a Regexp is given, the matching portion of the string is returned. If a String is given, that given string is returned if it occurs in the string. In both cases, nil is returned if there is no match.

str = "hello"
str.at(/lo/) # => "lo"
str.at(/ol/) # => nil
str.at("lo") # => "lo"
str.at("ol") # => nil
# File activesupport/lib/active_support/core_ext/string/access.rb, line 27
def at(position)
  self[position]
end
blank?()

A string is blank if it's empty or contains whitespaces only:

''.blank?       # => true
'   '.blank?    # => true
"\t\n\r".blank? # => true
' blah '.blank? # => false

Unicode whitespace is supported:

"\u00a0".blank? # => true

@return [true, false]

# File activesupport/lib/active_support/core_ext/object/blank.rb, line 115
def blank?
  BLANK_RE === self
end
camelcase(first_letter = :upper)
Alias for: camelize
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"
Also aliased as: camelcase
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 89
def camelize(first_letter = :upper)
  case first_letter
  when :upper
    ActiveSupport::Inflector.camelize(self, true)
  when :lower
    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"
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 187
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. See ActiveSupport::Inflector#constantize

'Module'.constantize  # => Module
'Class'.constantize   # => Class
'blargle'.constantize # => NameError: wrong constant name blargle
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 65
def constantize
  ActiveSupport::Inflector.constantize(self)
end
dasherize()

Replaces underscores with dashes in the string.

'puni_puni'.dasherize # => "puni-puni"
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 125
def dasherize
  ActiveSupport::Inflector.dasherize(self)
end
deconstantize()

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 activesupport/lib/active_support/core_ext/string/inflections.rb, line 150
def deconstantize
  ActiveSupport::Inflector.deconstantize(self)
end
demodulize()

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

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

See also deconstantize.

# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 137
def demodulize
  ActiveSupport::Inflector.demodulize(self)
end
exclude?(string)

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

"hello".exclude? "lo" # => false
"hello".exclude? "ol" # => true
"hello".exclude? ?h   # => false
# File activesupport/lib/active_support/core_ext/string/exclude.rb, line 8
def exclude?(string)
  !include?(string)
end
first(limit = 1)

Returns the first character. If a limit is supplied, returns a substring from the beginning of the string until it reaches the limit value. If the given limit is greater than or equal to the string length, returns a copy of self.

str = "hello"
str.first    # => "h"
str.first(1) # => "h"
str.first(2) # => "he"
str.first(0) # => ""
str.first(6) # => "hello"
# File activesupport/lib/active_support/core_ext/string/access.rb, line 75
def first(limit = 1)
  if limit == 0
    ''
  elsif limit >= size
    self.dup
  else
    to(limit - 1)
  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'.

'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 214
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 a substring from the given position to the end of the string. If the position is negative, it is counted from the end of the string.

str = "hello"
str.from(0)  # => "hello"
str.from(3)  # => "lo"
str.from(-2) # => "lo"

You can mix it with to method and do fun things like:

str = "hello"
str.from(0).to(-1) # => "hello"
str.from(1).to(-2) # => "ell"
# File activesupport/lib/active_support/core_ext/string/access.rb, line 44
def from(position)
  self[position..-1]
end
humanize(options = {})

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.

'employee_salary'.humanize              # => "Employee salary"
'author_id'.humanize                    # => "Author"
'author_id'.humanize(capitalize: false) # => "author"
'_id'.humanize                          # => "Id"
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 203
def humanize(options = {})
  ActiveSupport::Inflector.humanize(self, options)
end
in_time_zone(zone = ::Time.zone)

Converts String to a TimeWithZone in the current zone if Time#zone or Time.zone_default is set, otherwise converts String to a Time via #to_time

# File activesupport/lib/active_support/core_ext/string/zones.rb, line 7
def in_time_zone(zone = ::Time.zone)
  if zone
    ::Time.find_zone!(zone).parse(self)
  else
    to_time
  end
end
indent(amount, indent_string=nil, indent_empty_lines=false)

Indents the lines in the receiver:

<<EOS.indent(2)
def some_method
  some_code
end
EOS
# =>
  def some_method
    some_code
  end

The second argument, indent_string, specifies which indent string to use. The default is nil, which tells the method to make a guess by peeking at the first indented line, and fallback to a space if there is none.

"  foo".indent(2)        # => "    foo"
"foo\n\t\tbar".indent(2) # => "\t\tfoo\n\t\t\t\tbar"
"foo".indent(2, "\t")    # => "\t\tfoo"

While indent_string is typically one space or tab, it may be any string.

The third argument, indent_empty_lines, is a flag that says whether empty lines should be indented. Default is false.

"foo\n\nbar".indent(2)            # => "  foo\n\n  bar"
"foo\n\nbar".indent(2, nil, true) # => "  foo\n  \n  bar"
# File activesupport/lib/active_support/core_ext/string/indent.rb, line 40
def indent(amount, indent_string=nil, indent_empty_lines=false)
  dup.tap {|_| _.indent!(amount, indent_string, indent_empty_lines)}
end
indent!(amount, indent_string=nil, indent_empty_lines=false)

Same as indent, except it indents the receiver in-place.

Returns the indented string, or nil if there was nothing to indent.

# File activesupport/lib/active_support/core_ext/string/indent.rb, line 5
def indent!(amount, indent_string=nil, indent_empty_lines=false)
  indent_string = indent_string || self[/^[ \t]/] || ' '
  re = indent_empty_lines ? /^/ : /^(?!$)/
  gsub!(re, indent_string * amount)
end
inquiry()

Wraps the current string in the ActiveSupport::StringInquirer class, which gives you a prettier way to test for equality.

env = 'production'.inquiry
env.production?  # => true
env.development? # => false
# File activesupport/lib/active_support/core_ext/string/inquiry.rb, line 10
def inquiry
  ActiveSupport::StringInquirer.new(self)
end
is_utf8?()
# File activesupport/lib/active_support/core_ext/string/multibyte.rb, line 38
def is_utf8?
  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. If a limit is supplied, returns a substring from the end of the string until it reaches the limit value (counting backwards). If the given limit is greater than or equal to the string length, returns a copy of self.

str = "hello"
str.last    # => "o"
str.last(1) # => "o"
str.last(2) # => "lo"
str.last(0) # => ""
str.last(6) # => "hello"
# File activesupport/lib/active_support/core_ext/string/access.rb, line 95
def last(limit = 1)
  if limit == 0
    ''
  elsif limit >= size
    self.dup
  else
    from(-limit)
  end
end
mb_chars()

Multibyte proxy

mb_chars is a multibyte safe proxy for string methods.

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 encapsulated 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

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 behavior see ActiveSupport::Multibyte.

# File activesupport/lib/active_support/core_ext/string/multibyte.rb, line 34
def mb_chars
  ActiveSupport::Multibyte.proxy_class.new(self)
end
parameterize(sep = '-')

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) %>
# => <a href="/person/1-donald-e-knuth">Donald E. Knuth</a>
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 167
def parameterize(sep = '-')
  ActiveSupport::Inflector.parameterize(self, sep)
end
pluralize(count = nil, locale = :en)

Returns the plural form of the word in the string.

If the optional parameter count is specified, the singular form will be returned if count == 1. For any other value of count the plural will be returned.

If the optional parameter locale is specified, the word will be pluralized as a word of that language. By default, this parameter is set to :en. You must define your own inflection rules for languages other than English.

'post'.pluralize             # => "posts"
'octopus'.pluralize          # => "octopi"
'sheep'.pluralize            # => "sheep"
'words'.pluralize            # => "words"
'the blue mailman'.pluralize # => "the blue mailmen"
'CamelOctopus'.pluralize     # => "CamelOctopi"
'apple'.pluralize(1)         # => "apple"
'apple'.pluralize(2)         # => "apples"
'ley'.pluralize(:es)         # => "leyes"
'ley'.pluralize(1, :es)      # => "ley"
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 31
def pluralize(count = nil, locale = :en)
  locale = count if count.is_a?(Symbol)
  if count == 1
    self.dup
  else
    ActiveSupport::Inflector.pluralize(self, locale)
  end
end
remove(*patterns)

Returns a new string with all occurrences of the patterns removed.

str = "foo bar test"
str.remove(" test")                 # => "foo bar"
str                                 # => "foo bar test"
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 30
def remove(*patterns)
  dup.remove!(*patterns)
end
remove!(*patterns)

Alters the string by removing all occurrences of the patterns.

str = "foo bar test"
str.remove!(" test")                 # => "foo bar"
str                                  # => "foo bar"
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 38
def remove!(*patterns)
  patterns.each do |pattern|
    gsub! pattern, ""
  end

  self
end
safe_constantize()

safe_constantize tries to find a declared constant with the name specified in the string. It returns nil when the name is not in CamelCase or is not initialized. See ActiveSupport::Inflector#safe_constantize

'Module'.safe_constantize  # => Module
'Class'.safe_constantize   # => Class
'blargle'.safe_constantize # => nil
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 76
def safe_constantize
  ActiveSupport::Inflector.safe_constantize(self)
end
singularize(locale = :en)

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

If the optional parameter locale is specified, the word will be singularized as a word of that language. By default, this parameter is set to :en. You must define your own inflection rules for languages other than English.

'posts'.singularize            # => "post"
'octopi'.singularize           # => "octopus"
'sheep'.singularize            # => "sheep"
'word'.singularize             # => "word"
'the blue mailmen'.singularize # => "the blue mailman"
'CamelOctopi'.singularize      # => "CamelOctopus"
'leyes'.singularize(:es)       # => "ley"
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 54
def singularize(locale = :en)
  ActiveSupport::Inflector.singularize(self, locale)
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.

Note that it handles both ASCII and Unicode whitespace.

%{ 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 11
def squish
  dup.squish!
end
squish!()

Performs a destructive squish. See #squish.

str = " foo   bar    \n   \t   boo"
str.squish!                         # => "foo bar boo"
str                                 # => "foo bar boo"
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 19
def squish!
  gsub!(/\A[[:space:]]+/, '')
  gsub!(/[[:space:]]+\z/, '')
  gsub!(/[[:space:]]+/, ' ')
  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 177
def tableize
  ActiveSupport::Inflector.tableize(self)
end
titlecase()
Alias for: titleize
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"
Also aliased as: titlecase
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 107
def titleize
  ActiveSupport::Inflector.titleize(self)
end
to(position)

Returns a substring from the beginning of the string to the given position. If the position is negative, it is counted from the end of the string.

str = "hello"
str.to(0)  # => "h"
str.to(3)  # => "hell"
str.to(-2) # => "hell"

You can mix it with from method and do fun things like:

str = "hello"
str.from(0).to(-1) # => "hello"
str.from(1).to(-2) # => "ell"
# File activesupport/lib/active_support/core_ext/string/access.rb, line 61
def to(position)
  self[0..position]
end
to_date()

Converts a string to a Date value.

"1-1-2012".to_date   # => Sun, 01 Jan 2012
"01/01/2012".to_date # => Sun, 01 Jan 2012
"2012-12-13".to_date # => Thu, 13 Dec 2012
"12/13/2012".to_date # => ArgumentError: invalid date
# File activesupport/lib/active_support/core_ext/string/conversions.rb, line 43
def to_date
  ::Date.parse(self, false) unless blank?
end
to_datetime()

Converts a string to a DateTime value.

"1-1-2012".to_datetime            # => Sun, 01 Jan 2012 00:00:00 +0000
"01/01/2012 23:59:59".to_datetime # => Sun, 01 Jan 2012 23:59:59 +0000
"2012-12-13 12:50".to_datetime    # => Thu, 13 Dec 2012 12:50:00 +0000
"12/13/2012".to_datetime          # => ArgumentError: invalid date
# File activesupport/lib/active_support/core_ext/string/conversions.rb, line 53
def to_datetime
  ::DateTime.parse(self, false) unless blank?
end
to_time(form = :local)

Converts a string to a Time value. The form can be either :utc or :local (default :local).

The time is parsed using Time.parse method. If form is :local, then the time is in the system timezone. If the date part is missing then the current date is used and if the time part is missing then it is assumed to be 00:00:00.

"13-12-2012".to_time               # => 2012-12-13 00:00:00 +0100
"06:12".to_time                    # => 2012-12-13 06:12:00 +0100
"2012-12-13 06:12".to_time         # => 2012-12-13 06:12:00 +0100
"2012-12-13T06:12".to_time         # => 2012-12-13 06:12:00 +0100
"2012-12-13T06:12".to_time(:utc)   # => 2012-12-13 05:12:00 UTC
"12/13/2012".to_time               # => ArgumentError: argument out of range
# File activesupport/lib/active_support/core_ext/string/conversions.rb, line 19
def to_time(form = :local)
  parts = Date._parse(self, false)
  return if parts.empty?

  now = Time.now
  time = Time.new(
    parts.fetch(:year, now.year),
    parts.fetch(:mon, now.month),
    parts.fetch(:mday, now.day),
    parts.fetch(:hour, 0),
    parts.fetch(:min, 0),
    parts.fetch(:sec, 0) + parts.fetch(:sec_fraction, 0),
    parts.fetch(:offset, form == :utc ? 0 : nil)
  )

  form == :utc ? time.utc : time.getlocal
end
truncate(truncate_at, 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..."

Pass a string or regexp :separator to truncate text at a natural break:

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

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

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

'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 64
def truncate(truncate_at, options = {})
  return dup unless length > truncate_at

  omission = options[:omission] || '...'
  length_with_room_for_omission = truncate_at - omission.length
  stop =        if options[:separator]
      rindex(options[:separator], length_with_room_for_omission) || length_with_room_for_omission
    else
      length_with_room_for_omission
    end

  "#{self[0, stop]}#{omission}"
end
truncate_words(words_count, options = {})

Truncates a given text after a given number of words (words_count):

'Once upon a time in a world far far away'.truncate_words(4)
# => "Once upon a time..."

Pass a string or regexp :separator to specify a different separator of words:

'Once<br>upon<br>a<br>time<br>in<br>a<br>world'.truncate_words(5, separator: '<br>')
# => "Once<br>upon<br>a<br>time<br>in..."

The last characters will be replaced with the :omission string (defaults to “…”):

'And they found that many people were sleeping better.'.truncate_words(5, omission: '... (continued)')
# => "And they found that many... (continued)"
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 93
def truncate_words(words_count, options = {})
  sep = options[:separator] || /\s+/
  sep = Regexp.escape(sep.to_s) unless Regexp === sep
  if self =~ /\A((?:.+?#{sep}){#{words_count - 1}}.+?)#{sep}.*/m
    $1 + (options[:omission] || '...')
  else
    dup
  end
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.

'ActiveModel'.underscore         # => "active_model"
'ActiveModel::Errors'.underscore # => "active_model/errors"
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 118
def underscore
  ActiveSupport::Inflector.underscore(self)
end