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

Constants

BLANK_RE = /\A[[:space:]]*\z/
ENCODED_BLANKS = Concurrent::Map.new do |h, enc| h[enc] = Regexp.new(BLANK_RE.source.encode(enc), BLANK_RE.options | Regexp::FIXEDENCODING) end

Instance Public methods

acts_like_string?()

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

📝 Source code
# File activesupport/lib/active_support/core_ext/string/behavior.rb, line 5
  def acts_like_string?
    true
  end
🔎 See on GitHub

at(position)

If you pass a single integer, 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
📝 Source code
# File activesupport/lib/active_support/core_ext/string/access.rb, line 29
  def at(position)
    self[position]
  end
🔎 See on GitHub

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]

📝 Source code
# File activesupport/lib/active_support/core_ext/object/blank.rb, line 122
  def blank?
    # The regexp that matches blank strings is expensive. For the case of empty
    # strings we can speed up this method (~3.5x) with an empty? call. The
    # penalty for the rest of strings is marginal.
    empty? ||
      begin
        BLANK_RE.match?(self)
      rescue Encoding::CompatibilityError
        ENCODED_BLANKS[self.encoding].match?(self)
      end
  end
🔎 See on GitHub

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
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 91
  def camelize(first_letter = :upper)
    case first_letter
    when :upper
      ActiveSupport::Inflector.camelize(self, true)
    when :lower
      ActiveSupport::Inflector.camelize(self, false)
    else
      raise ArgumentError, "Invalid option, use either :upper or :lower."
    end
  end
🔎 See on GitHub

classify()

Creates 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.)

'ham_and_eggs'.classify # => "HamAndEgg"
'posts'.classify        # => "Post"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 210
  def classify
    ActiveSupport::Inflector.classify(self)
  end
🔎 See on GitHub

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
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 67
  def constantize
    ActiveSupport::Inflector.constantize(self)
  end
🔎 See on GitHub

dasherize()

Replaces underscores with dashes in the string.

'puni_puni'.dasherize # => "puni-puni"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 134
  def dasherize
    ActiveSupport::Inflector.dasherize(self)
  end
🔎 See on GitHub

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.

📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 159
  def deconstantize
    ActiveSupport::Inflector.deconstantize(self)
  end
🔎 See on GitHub

demodulize()

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

'ActiveSupport::Inflector::Inflections'.demodulize # => "Inflections"
'Inflections'.demodulize                           # => "Inflections"
'::Inflections'.demodulize                         # => "Inflections"
''.demodulize                                      # => ''

See also deconstantize.

📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 146
  def demodulize
    ActiveSupport::Inflector.demodulize(self)
  end
🔎 See on GitHub

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
📝 Source code
# File activesupport/lib/active_support/core_ext/string/exclude.rb, line 10
  def exclude?(string)
    !include?(string)
  end
🔎 See on GitHub

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"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/access.rb, line 77
  def first(limit = 1)
    if limit == 0
      ""
    elsif limit >= size
      dup
    else
      to(limit - 1)
    end
  end
🔎 See on GitHub

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"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 251
  def foreign_key(separate_class_name_and_id_with_underscore = true)
    ActiveSupport::Inflector.foreign_key(self, separate_class_name_and_id_with_underscore)
  end
🔎 See on GitHub

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"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/access.rb, line 46
  def from(position)
    self[position..-1]
  end
🔎 See on GitHub

html_safe()

Marks a string as trusted safe. It will be inserted into HTML with no additional escaping performed. It is your responsibility to ensure that the string contains no malicious content. This method is equivalent to the raw helper in views. It is recommended that you use sanitize instead of this method. It should never be called on user input.

📝 Source code
# File activesupport/lib/active_support/core_ext/string/output_safety.rb, line 283
  def html_safe
    ActiveSupport::SafeBuffer.new(self)
  end
🔎 See on GitHub

humanize(capitalize: true, keep_id_suffix: false)

Capitalizes the first word, turns underscores into spaces, and (by default)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.

The trailing '_id' can be kept and capitalized by setting the optional parameter keep_id_suffix to true. By default, this parameter is false.

'employee_salary'.humanize                    # => "Employee salary"
'author_id'.humanize                          # => "Author"
'author_id'.humanize(capitalize: false)       # => "author"
'_id'.humanize                                # => "Id"
'author_id'.humanize(keep_id_suffix: true)    # => "Author Id"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 231
  def humanize(capitalize: true, keep_id_suffix: false)
    ActiveSupport::Inflector.humanize(self, capitalize: capitalize, keep_id_suffix: keep_id_suffix)
  end
🔎 See on GitHub

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 String#to_time

📝 Source code
# File activesupport/lib/active_support/core_ext/string/zones.rb, line 9
  def in_time_zone(zone = ::Time.zone)
    if zone
      ::Time.find_zone!(zone).parse(self)
    else
      to_time
    end
  end
🔎 See on GitHub

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"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/indent.rb, line 42
  def indent(amount, indent_string = nil, indent_empty_lines = false)
    dup.tap { |_| _.indent!(amount, indent_string, indent_empty_lines) }
  end
🔎 See on GitHub

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.

📝 Source code
# File activesupport/lib/active_support/core_ext/string/indent.rb, line 7
  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
🔎 See on GitHub

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
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inquiry.rb, line 12
  def inquiry
    ActiveSupport::StringInquirer.new(self)
  end
🔎 See on GitHub

is_utf8?()

Returns true if string has utf_8 encoding.

utf_8_str = "some string".encode "UTF-8"
iso_str = "some string".encode "ISO-8859-1"

utf_8_str.is_utf8? # => true
iso_str.is_utf8?   # => false
📝 Source code
# File activesupport/lib/active_support/core_ext/string/multibyte.rb, line 47
  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
🔎 See on GitHub

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"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/access.rb, line 97
  def last(limit = 1)
    if limit == 0
      ""
    elsif limit >= size
      dup
    else
      from(-limit)
    end
  end
🔎 See on GitHub

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.

>> "lj".upcase
=> "lj"
>> "lj".mb_chars.upcase.to_s
=> "LJ"

NOTE: An above example is useful for pre Ruby 2.4. Ruby 2.4 supports Unicode case mappings.

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.

📝 Source code
# File activesupport/lib/active_support/core_ext/string/multibyte.rb, line 36
  def mb_chars
    ActiveSupport::Multibyte.proxy_class.new(self)
  end
🔎 See on GitHub

parameterize(separator: "-", preserve_case: false)

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>

To preserve the case of the characters in a string, use the preserve_case argument.

class Person
  def to_param
    "#{id}-#{name.parameterize(preserve_case: true)}"
  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>
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 190
  def parameterize(separator: "-", preserve_case: false)
    ActiveSupport::Inflector.parameterize(self, separator: separator, preserve_case: preserve_case)
  end
🔎 See on GitHub

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"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 33
  def pluralize(count = nil, locale = :en)
    locale = count if count.is_a?(Symbol)
    if count == 1
      dup
    else
      ActiveSupport::Inflector.pluralize(self, locale)
    end
  end
🔎 See on GitHub

remove(*patterns)

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

str = "foo bar test"
str.remove(" test")                 # => "foo bar"
str.remove(" test", /bar/)          # => "foo "
str                                 # => "foo bar test"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 32
  def remove(*patterns)
    dup.remove!(*patterns)
  end
🔎 See on GitHub

remove!(*patterns)

Alters the string by removing all occurrences of the patterns.

str = "foo bar test"
str.remove!(" test", /bar/)         # => "foo "
str                                 # => "foo "
📝 Source code
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 40
  def remove!(*patterns)
    patterns.each do |pattern|
      gsub! pattern, ""
    end

    self
  end
🔎 See on GitHub

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
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 78
  def safe_constantize
    ActiveSupport::Inflector.safe_constantize(self)
  end
🔎 See on GitHub

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"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 56
  def singularize(locale = :en)
    ActiveSupport::Inflector.singularize(self, locale)
  end
🔎 See on GitHub

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"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 13
  def squish
    dup.squish!
  end
🔎 See on GitHub

squish!()

Performs a destructive squish. See String#squish.

str = " foo   bar    \n   \t   boo"
str.squish!                         # => "foo bar boo"
str                                 # => "foo bar boo"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 21
  def squish!
    gsub!(/[[:space:]]+/, " ")
    strip!
    self
  end
🔎 See on GitHub

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 non-empty line in the whole string, and removes that amount of leading whitespace.

📝 Source code
# File activesupport/lib/active_support/core_ext/string/strip.rb, line 22
  def strip_heredoc
    gsub(/^#{scan(/^[ \t]*(?=\S)/).min}/, "".freeze)
  end
🔎 See on GitHub

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"
'ham_and_egg'.tableize     # => "ham_and_eggs"
'fancyCategory'.tableize   # => "fancy_categories"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 200
  def tableize
    ActiveSupport::Inflector.tableize(self)
  end
🔎 See on GitHub

titlecase(keep_id_suffix: false)

Alias for: titleize

titleize(keep_id_suffix: false)

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.

The trailing '_id','Id'.. can be kept and capitalized by setting the optional parameter keep_id_suffix to true. By default, this parameter is false.

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"
'string_ending_with_id'.titleize(keep_id_suffix: true)  # => "String Ending With Id"
Also aliased as: titlecase
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 116
  def titleize(keep_id_suffix: false)
    ActiveSupport::Inflector.titleize(self, keep_id_suffix: keep_id_suffix)
  end
🔎 See on GitHub

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"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/access.rb, line 63
  def to(position)
    self[0..position]
  end
🔎 See on GitHub

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
📝 Source code
# File activesupport/lib/active_support/core_ext/string/conversions.rb, line 46
  def to_date
    ::Date.parse(self, false) unless blank?
  end
🔎 See on GitHub

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
📝 Source code
# File activesupport/lib/active_support/core_ext/string/conversions.rb, line 56
  def to_datetime
    ::DateTime.parse(self, false) unless blank?
  end
🔎 See on GitHub

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 06:12:00 UTC
"12/13/2012".to_time               # => ArgumentError: argument out of range
📝 Source code
# File activesupport/lib/active_support/core_ext/string/conversions.rb, line 21
  def to_time(form = :local)
    parts = Date._parse(self, false)
    used_keys = %i(year mon mday hour min sec sec_fraction offset)
    return if (parts.keys & used_keys).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.to_time
  end
🔎 See on GitHub

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)"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 66
  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
🔎 See on GitHub

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)"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/filters.rb, line 95
  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
🔎 See on GitHub

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"
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 127
  def underscore
    ActiveSupport::Inflector.underscore(self)
  end
🔎 See on GitHub

upcase_first()

Converts just the first character to uppercase.

'what a Lovely Day'.upcase_first # => "What a Lovely Day"
'w'.upcase_first                 # => "W"
''.upcase_first                  # => ""
📝 Source code
# File activesupport/lib/active_support/core_ext/string/inflections.rb, line 240
  def upcase_first
    ActiveSupport::Inflector.upcase_first(self)
  end
🔎 See on GitHub