Chars enables you to work transparently with multibyte encodings 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 chars method. Methods which would normally return a String object now return a Chars object so methods can be chained.

  "The Perfect String  ".chars.downcase.strip.normalize #=> "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".chars.downcase.to_s

The actual operations on the string are delegated to handlers. Theoretically handlers can be implemented for any encoding, but the default handler handles UTF-8. This handler is set during initialization, if you want to use you own handler, you can set it on the Chars class. Look at the UTF8Handler source for an example how to implement your own handler. If you your own handler to work on anything but UTF-8 you probably also want to override Chars#handler.

  ActiveSupport::Multibyte::Chars.handler = MyHandler

Note that a few methods are defined on Chars instead of the handler because they are defined on Object or Kernel and method_missing can‘t catch them.

Methods
Included Modules
Attributes
[R] string
Public Class methods
handler=(klass)

Set the handler class for the Char objects.

     # File vendor/rails/activesupport/lib/active_support/multibyte/chars.rb, line 98
 98:     def self.handler=(klass)
 99:       @@handler = klass
100:     end
new(str)

Create a new Chars instance.

    # File vendor/rails/activesupport/lib/active_support/multibyte/chars.rb, line 45
45:     def initialize(str)
46:       @string = (str.string rescue str)
47:     end
Public Instance methods
<=>(other)

Returns -1, 0 or +1 depending on whether the Chars object is to be sorted before, equal or after the object on the right side of the operation. It accepts any object that implements to_s. See String.<=> for more details.

    # File vendor/rails/activesupport/lib/active_support/multibyte/chars.rb, line 52
52:     def <=>(other); @string <=> other.to_s; end
=~(other)

Like String.=~ only it returns the character offset (in codepoints) instead of the byte offset.

    # File vendor/rails/activesupport/lib/active_support/multibyte/chars.rb, line 64
64:     def =~(other)
65:       handler.translate_offset(@string, @string =~ other)
66:     end
gsub(*a, &b)

Gsub works exactly the same as gsub on a normal string.

    # File vendor/rails/activesupport/lib/active_support/multibyte/chars.rb, line 61
61:     def gsub(*a, &b); @string.gsub(*a, &b).chars; end
handler()

Returns the proper handler for the contained string depending on $KCODE and the encoding of the string. This method is used internally to always redirect messages to the proper classes depending on the context.

     # File vendor/rails/activesupport/lib/active_support/multibyte/chars.rb, line 104
104:     def handler
105:       if utf8_pragma?
106:         @@handler
107:       else
108:         ActiveSupport::Multibyte::Handlers::PassthruHandler
109:       end
110:     end
method_missing(m, *a, &b)

Try to forward all undefined methods to the handler, when a method is not defined on the handler, send it to the contained string. Method_missing is also responsible for making the bang! methods destructive.

    # File vendor/rails/activesupport/lib/active_support/multibyte/chars.rb, line 70
70:     def method_missing(m, *a, &b)
71:       begin
72:         # Simulate methods with a ! at the end because we can't touch the enclosed string from the handlers.
73:         if m.to_s =~ /^(.*)\!$/
74:           result = handler.send($1, @string, *a, &b)
75:           if result == @string
76:             result = nil
77:           else
78:             @string.replace result
79:           end
80:         else
81:           result = handler.send(m, @string, *a, &b)
82:         end
83:       rescue NoMethodError
84:         result = @string.send(m, *a, &b)
85:       rescue Handlers::EncodingError
86:         @string.replace handler.tidy_bytes(@string)
87:         retry
88:       end
89:       
90:       if result.kind_of?(String)
91:         result.chars
92:       else
93:         result
94:       end
95:     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.

    # File vendor/rails/activesupport/lib/active_support/multibyte/chars.rb, line 56
56:     def split(*args)
57:       @string.split(*args).map { |i| i.chars }
58:     end
to_str()

The magic method to make String and Chars comparable

    # File vendor/rails/activesupport/lib/active_support/multibyte/chars.rb, line 38
38:     def to_str
39:       # Using any other ways of overriding the String itself will lead you all the way from infinite loops to
40:       # core dumps. Don't go there.
41:       @string
42:     end