Class String < Object

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

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

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

  "".blank?                 # => true
  "   ".blank?              # => true
  "　".blank?               # => true
  " something here ".blank? # => false

Alias for camelize

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"

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"

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

Examples

  "Module".constantize  # => Module
  "Class".constantize   # => Class
  "blargle".constantize # => NameError: wrong constant name blargle

Replaces underscores with dashes in the string.

  "puni_puni" # => "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 constant expression in the string.

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

See also deconstantize.

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

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

Examples:

  "hello".first     # => "h"
  "hello".first(2)  # => "he"
  "hello".first(10) # => "hello"

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"

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

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"

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

  env = "production".inquiry
  env.production?  # => true
  env.development? # => false

Returns true if the string has UTF-8 semantics (a String used for purely byte resources is unlikely to have them), returns false otherwise.

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

Examples:

  "hello".last     # => "o"
  "hello".last(2)  # => "lo"
  "hello".last(10) # => "hello"

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 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

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 behavior see ActiveSupport::Multibyte.

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.

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>

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.

Examples

  "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"

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

Examples

  "Module".safe_constantize  # => Module
  "Class".safe_constantize   # => Class
  "blargle".safe_constantize # => nil

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"

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"

Performs a destructive squish. See String#squish.

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.

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"

Alias for 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"

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"

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

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

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

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 :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..."

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)"

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"