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Chars enables you to work transparently with UTF-8 encoding in the Ruby String class without having extensive knowledge about the encoding. A Chars object accepts a string upon initialization and proxies String methods in an encoding safe manner. All the normal String methods are also implemented on the proxy.

String methods are proxied through the Chars object, and can be accessed through the mb_chars method. Methods which would normally return a String object now return a Chars object so methods can be chained.

'The Perfect String  '.mb_chars.downcase.strip
# => #<ActiveSupport::Multibyte::Chars:0x007fdc434ccc10 @wrapped_string="the perfect string">

Chars objects are perfectly interchangeable with String objects as long as no explicit class checks are made. If certain methods do explicitly check the class, call to_s before you pass chars objects to them.

bad.explicit_checking_method 'T'.mb_chars.downcase.to_s

The default Chars implementation assumes that the encoding of the string is UTF-8, if you want to handle different encodings you can write your own multibyte string handler and configure it through ActiveSupport::Multibyte.proxy_class.

class CharsForUTF32
  def size
    @wrapped_string.size / 4
  end

  def self.accepts?(string)
    string.length % 4 == 0
  end
end

ActiveSupport::Multibyte.proxy_class = CharsForUTF32
Methods
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Included Modules
Attributes
[R] to_s
[R] to_str
[R] wrapped_string
Class Public methods
new(string)

Creates a new Chars instance by wrapping string.

# File activesupport/lib/active_support/multibyte/chars.rb, line 55
def initialize(string)
  @wrapped_string = string
  @wrapped_string.force_encoding(Encoding::UTF_8) unless @wrapped_string.frozen?
end
Instance Public methods
compose()

Performs composition on all the characters.

'é'.length                       # => 3
'é'.mb_chars.compose.to_s.length # => 2
# File activesupport/lib/active_support/multibyte/chars.rb, line 139
def compose
  chars(Unicode.compose(@wrapped_string.codepoints.to_a).pack("U*"))
end
decompose()

Performs canonical decomposition on all the characters.

'é'.length                         # => 2
'é'.mb_chars.decompose.to_s.length # => 3
# File activesupport/lib/active_support/multibyte/chars.rb, line 131
def decompose
  chars(Unicode.decompose(:canonical, @wrapped_string.codepoints.to_a).pack("U*"))
end
grapheme_length()

Returns the number of grapheme clusters in the string.

'क्षि'.mb_chars.length   # => 4
'क्षि'.mb_chars.grapheme_length # => 3
# File activesupport/lib/active_support/multibyte/chars.rb, line 147
def grapheme_length
  @wrapped_string.scan(/\X/).length
end
limit(limit)

Limits the byte size of the string to a number of bytes without breaking characters. Usable when the storage for a string is limited for some reason.

'こんにちは'.mb_chars.limit(7).to_s # => "こん"
# File activesupport/lib/active_support/multibyte/chars.rb, line 114
def limit(limit)
  chars(@wrapped_string.truncate_bytes(limit, omission: nil))
end
method_missing(method, *args, &block)

Forward all undefined methods to the wrapped string.

# File activesupport/lib/active_support/multibyte/chars.rb, line 61
def method_missing(method, *args, &block)
  result = @wrapped_string.__send__(method, *args, &block)
  if method.end_with?("!")
    self if result
  else
    result.kind_of?(String) ? chars(result) : result
  end
end
respond_to_missing?(method, include_private)

Returns true if obj responds to the given method. Private methods are included in the search only if the optional second parameter evaluates to true.

# File activesupport/lib/active_support/multibyte/chars.rb, line 73
def respond_to_missing?(method, include_private)
  @wrapped_string.respond_to?(method, include_private)
end
reverse()

Reverses all characters in the string.

'Café'.mb_chars.reverse.to_s # => 'éfaC'
# File activesupport/lib/active_support/multibyte/chars.rb, line 105
def reverse
  chars(@wrapped_string.scan(/\X/).reverse.join)
end
slice!(*args)

Works like String#slice!, but returns an instance of Chars, or nil if the string was not modified. The string will not be modified if the range given is out of bounds

string = 'Welcome'
string.mb_chars.slice!(3)    # => #<ActiveSupport::Multibyte::Chars:0x000000038109b8 @wrapped_string="c">
string # => 'Welome'
string.mb_chars.slice!(0..3) # => #<ActiveSupport::Multibyte::Chars:0x00000002eb80a0 @wrapped_string="Welo">
string # => 'me'
# File activesupport/lib/active_support/multibyte/chars.rb, line 95
def slice!(*args)
  string_sliced = @wrapped_string.slice!(*args)
  if string_sliced
    chars(string_sliced)
  end
end
split(*args)

Works just like String#split, with the exception that the items in the resulting list are Chars instances instead of String. This makes chaining methods easier.

'Café périferôl'.mb_chars.split(/é/).map { |part| part.upcase.to_s } # => ["CAF", " P", "RIFERÔL"]
# File activesupport/lib/active_support/multibyte/chars.rb, line 82
def split(*args)
  @wrapped_string.split(*args).map { |i| self.class.new(i) }
end
tidy_bytes(force = false)

Replaces all ISO-8859-1 or CP1252 characters by their UTF-8 equivalent resulting in a valid UTF-8 string.

Passing true will forcibly tidy all bytes, assuming that the string's encoding is entirely CP1252 or ISO-8859-1.

# File activesupport/lib/active_support/multibyte/chars.rb, line 156
def tidy_bytes(force = false)
  chars(Unicode.tidy_bytes(@wrapped_string, force))
end
titlecase()
Alias for: titleize
titleize()

Capitalizes the first letter of every word, when possible.

"ÉL QUE SE ENTERÓ".mb_chars.titleize.to_s    # => "Él Que Se Enteró"
"日本語".mb_chars.titleize.to_s               # => "日本語"
Also aliased as: titlecase
# File activesupport/lib/active_support/multibyte/chars.rb, line 122
def titleize
  chars(downcase.to_s.gsub(/\b('?\S)/u) { $1.upcase })
end