class String

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

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

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]

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"

See ActiveSupport::Inflector.camelize.

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"

See ActiveSupport::Inflector.classify.

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.

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

See ActiveSupport::Inflector.constantize.

Replaces underscores with dashes in the string.

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

See ActiveSupport::Inflector.dasherize.

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 ActiveSupport::Inflector.deconstantize.

See also 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 ActiveSupport::Inflector.demodulize.

See also deconstantize.

Converts the first character to lowercase.

'If they enjoyed The Matrix'.downcase_first # => "if they enjoyed The Matrix"
'I'.downcase_first                          # => "i"
''.downcase_first                           # => ""

See ActiveSupport::Inflector.downcase_first.

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. 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"

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"

See ActiveSupport::Inflector.foreign_key.

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"

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.

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"

See ActiveSupport::Inflector.humanize.

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

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 fall back 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"

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

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

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

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

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"

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

NOTE: Ruby 2.4 and later support native Unicode case mappings:

>> "lj".upcase
=> "LJ"

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.

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

If the optional parameter locale is specified, the word will be parameterized as a word of that language. By default, this parameter is set to nil and it will use the configured I18n.locale.

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>

See ActiveSupport::Inflector.parameterize.

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"

See ActiveSupport::Inflector.pluralize.

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"

Alters the string by removing all occurrences of the patterns.

str = "foo bar test"
str.remove!(" test", /bar/)         # => "foo "
str                                 # => "foo "

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.

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

See ActiveSupport::Inflector.safe_constantize.

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"

See ActiveSupport::Inflector.singularize.

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"

Performs a destructive squish. See String#squish.

str = " foo   bar    \n   \t   boo"
str.squish!                         # => "foo bar boo"
str                                 # => "foo bar boo"

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.

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"

See ActiveSupport::Inflector.tableize.

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.

'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"

See ActiveSupport::Inflector.titleize.

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"

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

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
"1604326192".to_time               # => ArgumentError: argument out of range

Truncates a given text to length truncate_to if text is longer than truncate_to:

'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 “…”). The total length will not exceed truncate_to unless both text and :omission are longer than truncate_to:

'And they found that many people were sleeping better.'.truncate(25, omission: '... (continued)')
# => "And they f... (continued)"

'And they found that many people were sleeping better.'.truncate(4, omission: '... (continued)')
# => "... (continued)"

Truncates text to at most truncate_to bytes in length without breaking string encoding by splitting multibyte characters or breaking grapheme clusters (“perceptual characters”) by truncating at combining characters.

>> "🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪".size
=> 20
>> "🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪".bytesize
=> 80
>> "🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪🔪".truncate_bytes(20)
=> "🔪🔪🔪🔪…"

The truncated text ends with the :omission string, defaulting to “…”, for a total length not exceeding truncate_to.

Raises ArgumentError when the bytesize of :omission exceeds truncate_to.

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)"

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"

See ActiveSupport::Inflector.underscore.

Converts the first character to uppercase.

'what a Lovely Day'.upcase_first # => "What a Lovely Day"
'w'.upcase_first                 # => "W"
''.upcase_first                  # => ""

See ActiveSupport::Inflector.upcase_first.