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.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".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
Returns true
when the proxy class can handle the string.
Returns false
otherwise.
# File lib/active_support/multibyte/chars.rb, line 75 def self.consumes?(string) # Unpack is a little bit faster than regular expressions. string.unpack('U*') true rescue ArgumentError false end
Creates a new Chars instance by wrapping string.
# File lib/active_support/multibyte/chars.rb, line 42 def initialize(string) @wrapped_string = string @wrapped_string.force_encoding(Encoding::UTF_8) unless @wrapped_string.frozen? end
Returns true
if the Chars class can
and should act as a proxy for the string string. Returns
false
otherwise.
# File lib/active_support/multibyte/chars.rb, line 99 def self.wants?(string) $KCODE == 'UTF8' && consumes?(string) end
Returns a new Chars object containing the other object concatenated to the string.
Example:
('Café'.mb_chars + ' périferôl').to_s # => "Café périferôl"
# File lib/active_support/multibyte/chars.rb, line 107 def +(other) chars(@wrapped_string + other) end
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
:
'é'.mb_chars <=> 'ü'.mb_chars # => -1
See String#<=>
for more details.
# File lib/active_support/multibyte/chars.rb, line 92 def <=>(other) @wrapped_string <=> other.to_s end
Like String#=~
only it returns the character offset (in
codepoints) instead of the byte offset.
Example:
'Café périferôl'.mb_chars =~ /ô/ # => 12
# File lib/active_support/multibyte/chars.rb, line 115 def =~(other) translate_offset(@wrapped_string =~ other) end
Like String#[]=
, except instead of byte offsets you specify
character offsets.
Example:
s = "Müller" s.mb_chars[2] = "e" # Replace character with offset 2 s # => "Müeler" s = "Müller" s.mb_chars[1, 2] = "ö" # Replace 2 characters at character offset 1 s # => "Möler"
# File lib/active_support/multibyte/chars.rb, line 265 def []=(*args) replace_by = args.pop # Indexed replace with regular expressions already works if args.first.is_a?(Regexp) @wrapped_string[*args] = replace_by else result = Unicode.u_unpack(@wrapped_string) case args.first when Fixnum raise IndexError, "index #{args[0]} out of string" if args[0] >= result.length min = args[0] max = args[1].nil? ? min : (min + args[1] - 1) range = Range.new(min, max) replace_by = [replace_by].pack('U') if replace_by.is_a?(Fixnum) when Range raise RangeError, "#{args[0]} out of range" if args[0].min >= result.length range = args[0] else needle = args[0].to_s min = index(needle) max = min + Unicode.u_unpack(needle).length - 1 range = Range.new(min, max) end result[range] = Unicode.u_unpack(replace_by) @wrapped_string.replace(result.pack('U*')) end end
Enable more predictable duck-typing on String-like classes. See Object#acts_like?.
# File lib/active_support/multibyte/chars.rb, line 70 def acts_like_string? true end
Converts the first character to uppercase and the remainder to lowercase.
Example:
'über'.mb_chars.capitalize.to_s # => "Über"
# File lib/active_support/multibyte/chars.rb, line 358 def capitalize (slice(0) || chars('')).upcase + (slice(1..-1) || chars('')).downcase end
Works just like String#center
, only integer specifies
characters instead of bytes.
Example:
"¾ cup".mb_chars.center(8).to_s # => " ¾ cup " "¾ cup".mb_chars.center(8, " ").to_s # Use non-breaking whitespace # => " ¾ cup "
# File lib/active_support/multibyte/chars.rb, line 233 def center(integer, padstr=' ') justify(integer, :center, padstr) end
Performs composition on all the characters.
Example:
'é'.length # => 3 'é'.mb_chars.compose.to_s.length # => 2
# File lib/active_support/multibyte/chars.rb, line 396 def compose chars(Unicode.compose_codepoints(Unicode.u_unpack(@wrapped_string)).pack('U*')) end
Performs canonical decomposition on all the characters.
Example:
'é'.length # => 2 'é'.mb_chars.decompose.to_s.length # => 3
# File lib/active_support/multibyte/chars.rb, line 387 def decompose chars(Unicode.decompose_codepoints(:canonical, Unicode.u_unpack(@wrapped_string)).pack('U*')) end
Convert characters in the string to lowercase.
Example:
'VĚDA A VÝZKUM'.mb_chars.downcase.to_s # => "věda a výzkum"
# File lib/active_support/multibyte/chars.rb, line 350 def downcase chars(Unicode.apply_mapping @wrapped_string, :lowercase_mapping) end
Returns the number of grapheme clusters in the string.
Example:
'क्षि'.mb_chars.length # => 4 'क्षि'.mb_chars.g_length # => 3
# File lib/active_support/multibyte/chars.rb, line 405 def g_length Unicode.g_unpack(@wrapped_string).length end
Returns true
if contained string contains other.
Returns false
otherwise.
Example:
'Café'.mb_chars.include?('é') # => true
# File lib/active_support/multibyte/chars.rb, line 139 def include?(other) # We have to redefine this method because Enumerable defines it. @wrapped_string.include?(other) end
Returns the position needle in the string, counting in codepoints.
Returns nil
if needle isn't found.
Example:
'Café périferôl'.mb_chars.index('ô') # => 12 'Café périferôl'.mb_chars.index(/\w/) # => 0
# File lib/active_support/multibyte/chars.rb, line 149 def index(needle, offset=0) wrapped_offset = first(offset).wrapped_string.length index = @wrapped_string.index(needle, wrapped_offset) index ? (Unicode.u_unpack(@wrapped_string.slice(0...index)).size) : nil end
Inserts the passed string at specified codepoint offsets.
Example:
'Café'.mb_chars.insert(4, ' périferôl').to_s # => "Café périferôl"
# File lib/active_support/multibyte/chars.rb, line 123 def insert(offset, fragment) unpacked = Unicode.u_unpack(@wrapped_string) unless offset > unpacked.length @wrapped_string.replace( Unicode.u_unpack(@wrapped_string).insert(offset, *Unicode.u_unpack(fragment)).pack('U*') ) else raise IndexError, "index #{offset} out of string" end self end
Limit 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.
Example:
'こんにちは'.mb_chars.limit(7).to_s # => "こん"
# File lib/active_support/multibyte/chars.rb, line 334 def limit(limit) slice(0...translate_offset(limit)) end
Works just like String#ljust
, only integer specifies
characters instead of bytes.
Example:
"¾ cup".mb_chars.rjust(8).to_s # => "¾ cup " "¾ cup".mb_chars.rjust(8, " ").to_s # Use non-breaking whitespace # => "¾ cup "
# File lib/active_support/multibyte/chars.rb, line 220 def ljust(integer, padstr=' ') justify(integer, :left, padstr) end
Strips entire range of Unicode whitespace from the left of the string.
# File lib/active_support/multibyte/chars.rb, line 181 def lstrip chars(@wrapped_string.gsub(Unicode::LEADERS_PAT, '')) end
Forward all undefined methods to the wrapped string.
# File lib/active_support/multibyte/chars.rb, line 53 def method_missing(method, *args, &block) if method.to_s =~ /!$/ @wrapped_string.__send__(method, *args, &block) self else result = @wrapped_string.__send__(method, *args, &block) result.kind_of?(String) ? chars(result) : result end end
Returns the KC normalization of the string by default. NFKC is considered the best normalization form for passing strings to databases and validations.
form
- The form you want to normalize in. Should be one of the
following: :c
, :kc
, :d
, or
:kd
. Default is ActiveSupport::Multibyte::Unicode#default_normalization_form
# File lib/active_support/multibyte/chars.rb, line 378 def normalize(form = nil) chars(Unicode.normalize(@wrapped_string, form)) end
Returns the codepoint of the first character in the string.
Example:
'こんにちは'.mb_chars.ord # => 12371
# File lib/active_support/multibyte/chars.rb, line 194 def ord Unicode.u_unpack(@wrapped_string)[0] end
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 lib/active_support/multibyte/chars.rb, line 65 def respond_to?(method, include_private=false) super || @wrapped_string.respond_to?(method, include_private) end
Reverses all characters in the string.
Example:
'Café'.mb_chars.reverse.to_s # => 'éfaC'
# File lib/active_support/multibyte/chars.rb, line 297 def reverse chars(Unicode.g_unpack(@wrapped_string).reverse.flatten.pack('U*')) end
Returns the position needle in the string, counting in codepoints,
searching backward from offset or the end of the string. Returns
nil
if needle isn't found.
Example:
'Café périferôl'.mb_chars.rindex('é') # => 6 'Café périferôl'.mb_chars.rindex(/\w/) # => 13
# File lib/active_support/multibyte/chars.rb, line 162 def rindex(needle, offset=nil) offset ||= length wrapped_offset = first(offset).wrapped_string.length index = @wrapped_string.rindex(needle, wrapped_offset) index ? (Unicode.u_unpack(@wrapped_string.slice(0...index)).size) : nil end
Works just like String#rjust
, only integer specifies
characters instead of bytes.
Example:
"¾ cup".mb_chars.rjust(8).to_s # => " ¾ cup" "¾ cup".mb_chars.rjust(8, " ").to_s # Use non-breaking whitespace # => " ¾ cup"
# File lib/active_support/multibyte/chars.rb, line 207 def rjust(integer, padstr=' ') justify(integer, :right, padstr) end
Strips entire range of Unicode whitespace from the right of the string.
# File lib/active_support/multibyte/chars.rb, line 176 def rstrip chars(@wrapped_string.gsub(Unicode::TRAILERS_PAT, '')) end
Returns the number of codepoints in the string
# File lib/active_support/multibyte/chars.rb, line 170 def size Unicode.u_unpack(@wrapped_string).size end
Implements Unicode-aware slice with codepoints. Slicing on one point returns the codepoints for that character.
Example:
'こんにちは'.mb_chars.slice(2..3).to_s # => "にち"
# File lib/active_support/multibyte/chars.rb, line 306 def slice(*args) if args.size > 2 raise ArgumentError, "wrong number of arguments (#{args.size} for 1)" # Do as if we were native elsif (args.size == 2 && !(args.first.is_a?(Numeric) || args.first.is_a?(Regexp))) raise TypeError, "cannot convert #{args.first.class} into Integer" # Do as if we were native elsif (args.size == 2 && !args[1].is_a?(Numeric)) raise TypeError, "cannot convert #{args[1].class} into Integer" # Do as if we were native elsif args[0].kind_of? Range cps = Unicode.u_unpack(@wrapped_string).slice(*args) result = cps.nil? ? nil : cps.pack('U*') elsif args[0].kind_of? Regexp result = @wrapped_string.slice(*args) elsif args.size == 1 && args[0].kind_of?(Numeric) character = Unicode.u_unpack(@wrapped_string)[args[0]] result = character && [character].pack('U') else cps = Unicode.u_unpack(@wrapped_string).slice(*args) result = cps && cps.pack('U*') end result && chars(result) end
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.
Example:
'Café périferôl'.mb_chars.split(/é/).map { |part| part.upcase.to_s } # => ["CAF", " P", "RIFERÔL"]
# File lib/active_support/multibyte/chars.rb, line 248 def split(*args) @wrapped_string.split(*args).map { |i| i.mb_chars } end
Strips entire range of Unicode whitespace from the right and left of the string.
# File lib/active_support/multibyte/chars.rb, line 186 def strip rstrip.lstrip end
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 lib/active_support/multibyte/chars.rb, line 412 def tidy_bytes(force = false) chars(Unicode.tidy_bytes(@wrapped_string, force)) end
Capitalizes the first letter of every word, when possible.
Example:
"ÉL QUE SE ENTERÓ".mb_chars.titleize # => "Él Que Se Enteró" "日本語".mb_chars.titleize # => "日本語"
# File lib/active_support/multibyte/chars.rb, line 367 def titleize chars(downcase.to_s.gsub(/\b('?[\S])/) { Unicode.apply_mapping $1, :uppercase_mapping }) end
Convert characters in the string to uppercase.
Example:
'Laurent, où sont les tests ?'.mb_chars.upcase.to_s # => "LAURENT, OÙ SONT LES TESTS ?"
# File lib/active_support/multibyte/chars.rb, line 342 def upcase chars(Unicode.apply_mapping @wrapped_string, :uppercase_mapping) end