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 76 76: def self.consumes?(string) 77: # Unpack is a little bit faster than regular expressions. 78: string.unpack('U*') 79: true 80: rescue ArgumentError 81: false 82: end
Creates a new Chars instance by wrapping string.
# File lib/active_support/multibyte/chars.rb, line 43 43: def initialize(string) 44: @wrapped_string = string 45: @wrapped_string.force_encoding(Encoding::UTF_8) unless @wrapped_string.frozen? 46: 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 100 100: def self.wants?(string) 101: $KCODE == 'UTF8' && consumes?(string) 102: 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 108 108: def +(other) 109: chars(@wrapped_string + other) 110: 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 93 93: def <=>(other) 94: @wrapped_string <=> other.to_s 95: 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 116 116: def =~(other) 117: translate_offset(@wrapped_string =~ other) 118: end
# File lib/active_support/multibyte/chars.rb, line 239 239: def =~(other) 240: @wrapped_string =~ other 241: 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 266 266: def []=(*args) 267: replace_by = args.pop 268: # Indexed replace with regular expressions already works 269: if args.first.is_a?(Regexp) 270: @wrapped_string[*args] = replace_by 271: else 272: result = Unicode.u_unpack(@wrapped_string) 273: if args[0].is_a?(Fixnum) 274: raise IndexError, "index #{args[0]} out of string" if args[0] >= result.length 275: min = args[0] 276: max = args[1].nil? ? min : (min + args[1] - 1) 277: range = Range.new(min, max) 278: replace_by = [replace_by].pack('U') if replace_by.is_a?(Fixnum) 279: elsif args.first.is_a?(Range) 280: raise RangeError, "#{args[0]} out of range" if args[0].min >= result.length 281: range = args[0] 282: else 283: needle = args[0].to_s 284: min = index(needle) 285: max = min + Unicode.u_unpack(needle).length - 1 286: range = Range.new(min, max) 287: end 288: result[range] = Unicode.u_unpack(replace_by) 289: @wrapped_string.replace(result.pack('U*')) 290: end 291: end
Enable more predictable duck-typing on String-like classes. See Object#acts_like?.
# File lib/active_support/multibyte/chars.rb, line 71 71: def acts_like_string? 72: true 73: 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 359 359: def capitalize 360: (slice(0) || chars('')).upcase + (slice(1..1) || chars('')).downcase 361: 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 234 234: def center(integer, padstr=' ') 235: justify(integer, :center, padstr) 236: 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 397 397: def compose 398: chars(Unicode.compose_codepoints(Unicode.u_unpack(@wrapped_string)).pack('U*')) 399: 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 388 388: def decompose 389: chars(Unicode.decompose_codepoints(:canonical, Unicode.u_unpack(@wrapped_string)).pack('U*')) 390: 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 351 351: def downcase 352: chars(Unicode.apply_mapping @wrapped_string, :lowercase_mapping) 353: 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 406 406: def g_length 407: Unicode.g_unpack(@wrapped_string).length 408: 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 140 140: def include?(other) 141: # We have to redefine this method because Enumerable defines it. 142: @wrapped_string.include?(other) 143: 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/u) # => 0
# File lib/active_support/multibyte/chars.rb, line 150 150: def index(needle, offset=0) 151: wrapped_offset = first(offset).wrapped_string.length 152: index = @wrapped_string.index(needle, wrapped_offset) 153: index ? (Unicode.u_unpack(@wrapped_string.slice(0...index)).size) : nil 154: 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 124 124: def insert(offset, fragment) 125: unpacked = Unicode.u_unpack(@wrapped_string) 126: unless offset > unpacked.length 127: @wrapped_string.replace( 128: Unicode.u_unpack(@wrapped_string).insert(offset, *Unicode.u_unpack(fragment)).pack('U*') 129: ) 130: else 131: raise IndexError, "index #{offset} out of string" 132: end 133: self 134: 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:
s = 'こんにちは' s.mb_chars.limit(7) # => "こに"
# File lib/active_support/multibyte/chars.rb, line 335 335: def limit(limit) 336: slice(0...translate_offset(limit)) 337: 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 221 221: def ljust(integer, padstr=' ') 222: justify(integer, :left, padstr) 223: end
Strips entire range of Unicode whitespace from the left of the string.
# File lib/active_support/multibyte/chars.rb, line 182 182: def lstrip 183: chars(@wrapped_string.gsub(Unicode::LEADERS_PAT, '')) 184: end
Forward all undefined methods to the wrapped string.
# File lib/active_support/multibyte/chars.rb, line 54 54: def method_missing(method, *args, &block) 55: if method.to_s =~ /!$/ 56: @wrapped_string.__send__(method, *args, &block) 57: self 58: else 59: result = @wrapped_string.__send__(method, *args, &block) 60: result.kind_of?(String) ? chars(result) : result 61: end 62: 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 379 379: def normalize(form = nil) 380: chars(Unicode.normalize(@wrapped_string, form)) 381: 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 195 195: def ord 196: Unicode.u_unpack(@wrapped_string)[0] 197: 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 66 66: def respond_to?(method, include_private=false) 67: super || @wrapped_string.respond_to?(method, include_private) || false 68: end
Reverses all characters in the string.
Example:
'Café'.mb_chars.reverse.to_s # => 'éfaC'
# File lib/active_support/multibyte/chars.rb, line 297 297: def reverse 298: chars(Unicode.g_unpack(@wrapped_string).reverse.flatten.pack('U*')) 299: 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/u) # => 13
# File lib/active_support/multibyte/chars.rb, line 163 163: def rindex(needle, offset=nil) 164: offset ||= length 165: wrapped_offset = first(offset).wrapped_string.length 166: index = @wrapped_string.rindex(needle, wrapped_offset) 167: index ? (Unicode.u_unpack(@wrapped_string.slice(0...index)).size) : nil 168: 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 208 208: def rjust(integer, padstr=' ') 209: justify(integer, :right, padstr) 210: end
Strips entire range of Unicode whitespace from the right of the string.
# File lib/active_support/multibyte/chars.rb, line 177 177: def rstrip 178: chars(@wrapped_string.gsub(Unicode::TRAILERS_PAT, '')) 179: end
Returns the number of codepoints in the string
# File lib/active_support/multibyte/chars.rb, line 171 171: def size 172: Unicode.u_unpack(@wrapped_string).size 173: 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 306 306: def slice(*args) 307: if args.size > 2 308: raise ArgumentError, "wrong number of arguments (#{args.size} for 1)" # Do as if we were native 309: elsif (args.size == 2 && !(args.first.is_a?(Numeric) || args.first.is_a?(Regexp))) 310: raise TypeError, "cannot convert #{args.first.class} into Integer" # Do as if we were native 311: elsif (args.size == 2 && !args[1].is_a?(Numeric)) 312: raise TypeError, "cannot convert #{args[1].class} into Integer" # Do as if we were native 313: elsif args[0].kind_of? Range 314: cps = Unicode.u_unpack(@wrapped_string).slice(*args) 315: result = cps.nil? ? nil : cps.pack('U*') 316: elsif args[0].kind_of? Regexp 317: result = @wrapped_string.slice(*args) 318: elsif args.size == 1 && args[0].kind_of?(Numeric) 319: character = Unicode.u_unpack(@wrapped_string)[args[0]] 320: result = character && [character].pack('U') 321: else 322: cps = Unicode.u_unpack(@wrapped_string).slice(*args) 323: result = cps && cps.pack('U*') 324: end 325: result && chars(result) 326: 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 249 249: def split(*args) 250: @wrapped_string.split(*args).map { |i| i.mb_chars } 251: end
Strips entire range of Unicode whitespace from the right and left of the string.
# File lib/active_support/multibyte/chars.rb, line 187 187: def strip 188: rstrip.lstrip 189: 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 413 413: def tidy_bytes(force = false) 414: chars(Unicode.tidy_bytes(@wrapped_string, force)) 415: 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 368 368: def titleize 369: chars(downcase.to_s.gsub(/\b('?[\S])/) { Unicode.apply_mapping $1, :uppercase_mapping }) 370: 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 343 343: def upcase 344: chars(Unicode.apply_mapping @wrapped_string, :uppercase_mapping) 345: end
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