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 Mail::Multibyte.proxy_class.
class CharsForUTF32 def size @wrapped_string.size / 4 end def self.accepts?(string) string.length % 4 == 0 end end Mail::Multibyte.proxy_class = CharsForUTF32
Returns true when the proxy class can handle the string. Returns false otherwise.
# File lib/mail/multibyte/chars.rb, line 74 74: def self.consumes?(string) 75: # Unpack is a little bit faster than regular expressions. 76: string.unpack('U*') 77: true 78: rescue ArgumentError 79: false 80: end
Creates a new Chars instance by wrapping string.
# File lib/mail/multibyte/chars.rb, line 41 41: def initialize(string) 42: @wrapped_string = string 43: @wrapped_string.force_encoding(Encoding::UTF_8) unless @wrapped_string.frozen? 44: end
Returns true if the Chars class can and should act as a proxy for the string string. Returns false otherwise.
# File lib/mail/multibyte/chars.rb, line 98 98: def self.wants?(string) 99: $KCODE == 'UTF8' && consumes?(string) 100: 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/mail/multibyte/chars.rb, line 106 106: def +(other) 107: chars(@wrapped_string + other) 108: 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/mail/multibyte/chars.rb, line 91 91: def <=>(other) 92: @wrapped_string <=> other.to_s 93: 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/mail/multibyte/chars.rb, line 114 114: def =~(other) 115: translate_offset(@wrapped_string =~ other) 116: end
# File lib/mail/multibyte/chars.rb, line 237 237: def =~(other) 238: @wrapped_string =~ other 239: 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/mail/multibyte/chars.rb, line 264 264: def []=(*args) 265: replace_by = args.pop 266: # Indexed replace with regular expressions already works 267: if args.first.is_a?(Regexp) 268: @wrapped_string[*args] = replace_by 269: else 270: result = Unicode.u_unpack(@wrapped_string) 271: if args[0].is_a?(Fixnum) 272: raise IndexError, "index #{args[0]} out of string" if args[0] >= result.length 273: min = args[0] 274: max = args[1].nil? ? min : (min + args[1] - 1) 275: range = Range.new(min, max) 276: replace_by = [replace_by].pack('U') if replace_by.is_a?(Fixnum) 277: elsif args.first.is_a?(Range) 278: raise RangeError, "#{args[0]} out of range" if args[0].min >= result.length 279: range = args[0] 280: else 281: needle = args[0].to_s 282: min = index(needle) 283: max = min + Unicode.u_unpack(needle).length - 1 284: range = Range.new(min, max) 285: end 286: result[range] = Unicode.u_unpack(replace_by) 287: @wrapped_string.replace(result.pack('U*')) 288: end 289: end
Enable more predictable duck-typing on String-like classes. See Object#acts_like?.
# File lib/mail/multibyte/chars.rb, line 69 69: def acts_like_string? 70: true 71: end
Converts the first character to uppercase and the remainder to lowercase.
Example:
'über'.mb_chars.capitalize.to_s # => "Über"
# File lib/mail/multibyte/chars.rb, line 357 357: def capitalize 358: (slice(0) || chars('')).upcase + (slice(1..1) || chars('')).downcase 359: 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/mail/multibyte/chars.rb, line 232 232: def center(integer, padstr=' ') 233: justify(integer, :center, padstr) 234: end
Performs composition on all the characters.
Example:
'é'.length # => 3 'é'.mb_chars.compose.to_s.length # => 2
# File lib/mail/multibyte/chars.rb, line 395 395: def compose 396: chars(Unicode.compose_codepoints(Unicode.u_unpack(@wrapped_string)).pack('U*')) 397: end
Performs canonical decomposition on all the characters.
Example:
'é'.length # => 2 'é'.mb_chars.decompose.to_s.length # => 3
# File lib/mail/multibyte/chars.rb, line 386 386: def decompose 387: chars(Unicode.decompose_codepoints(:canonical, Unicode.u_unpack(@wrapped_string)).pack('U*')) 388: end
Convert characters in the string to lowercase.
Example:
'VĚDA A VÝZKUM'.mb_chars.downcase.to_s # => "věda a výzkum"
# File lib/mail/multibyte/chars.rb, line 349 349: def downcase 350: chars(Unicode.apply_mapping(@wrapped_string), :lowercase_mapping) 351: end
Returns the number of grapheme clusters in the string.
Example:
'क्षि'.mb_chars.length # => 4 'क्षि'.mb_chars.g_length # => 3
# File lib/mail/multibyte/chars.rb, line 404 404: def g_length 405: Unicode.g_unpack(@wrapped_string).length 406: end
Returns true if contained string contains other. Returns false otherwise.
Example:
'Café'.mb_chars.include?('é') # => true
# File lib/mail/multibyte/chars.rb, line 138 138: def include?(other) 139: # We have to redefine this method because Enumerable defines it. 140: @wrapped_string.include?(other) 141: 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/mail/multibyte/chars.rb, line 148 148: def index(needle, offset=0) 149: wrapped_offset = first(offset).wrapped_string.length 150: index = @wrapped_string.index(needle, wrapped_offset) 151: index ? (Unicode.u_unpack(@wrapped_string.slice(0...index)).size) : nil 152: end
Inserts the passed string at specified codepoint offsets.
Example:
'Café'.mb_chars.insert(4, ' périferôl').to_s # => "Café périferôl"
# File lib/mail/multibyte/chars.rb, line 122 122: def insert(offset, fragment) 123: unpacked = Unicode.u_unpack(@wrapped_string) 124: unless offset > unpacked.length 125: @wrapped_string.replace( 126: Unicode.u_unpack(@wrapped_string).insert(offset, *Unicode.u_unpack(fragment)).pack('U*') 127: ) 128: else 129: raise IndexError, "index #{offset} out of string" 130: end 131: self 132: 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/mail/multibyte/chars.rb, line 333 333: def limit(limit) 334: slice(0...translate_offset(limit)) 335: 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/mail/multibyte/chars.rb, line 219 219: def ljust(integer, padstr=' ') 220: justify(integer, :left, padstr) 221: end
Strips entire range of Unicode whitespace from the left of the string.
# File lib/mail/multibyte/chars.rb, line 180 180: def lstrip 181: chars(@wrapped_string.gsub(Unicode::LEADERS_PAT, '')) 182: end
Forward all undefined methods to the wrapped string.
# File lib/mail/multibyte/chars.rb, line 52 52: def method_missing(method, *args, &block) 53: if method.to_s =~ /!$/ 54: @wrapped_string.__send__(method, *args, &block) 55: self 56: else 57: result = @wrapped_string.__send__(method, *args, &block) 58: result.kind_of?(String) ? chars(result) : result 59: end 60: 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 Mail::Multibyte::Unicode.default_normalization_form
# File lib/mail/multibyte/chars.rb, line 377 377: def normalize(form = nil) 378: chars(Unicode.normalize(@wrapped_string, form)) 379: end
Returns the codepoint of the first character in the string.
Example:
'こんにちは'.mb_chars.ord # => 12371
# File lib/mail/multibyte/chars.rb, line 193 193: def ord 194: Unicode.u_unpack(@wrapped_string)[0] 195: 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/mail/multibyte/chars.rb, line 64 64: def respond_to?(method, include_private=false) 65: super || @wrapped_string.respond_to?(method, include_private) || false 66: end
Reverses all characters in the string.
Example:
'Café'.mb_chars.reverse.to_s # => 'éfaC'
# File lib/mail/multibyte/chars.rb, line 295 295: def reverse 296: chars(Unicode.g_unpack(@wrapped_string).reverse.flatten.pack('U*')) 297: 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/mail/multibyte/chars.rb, line 161 161: def rindex(needle, offset=nil) 162: offset ||= length 163: wrapped_offset = first(offset).wrapped_string.length 164: index = @wrapped_string.rindex(needle, wrapped_offset) 165: index ? (Unicode.u_unpack(@wrapped_string.slice(0...index)).size) : nil 166: 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/mail/multibyte/chars.rb, line 206 206: def rjust(integer, padstr=' ') 207: justify(integer, :right, padstr) 208: end
Strips entire range of Unicode whitespace from the right of the string.
# File lib/mail/multibyte/chars.rb, line 175 175: def rstrip 176: chars(@wrapped_string.gsub(Unicode::TRAILERS_PAT, '')) 177: end
Returns the number of codepoints in the string
# File lib/mail/multibyte/chars.rb, line 169 169: def size 170: Unicode.u_unpack(@wrapped_string).size 171: 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/mail/multibyte/chars.rb, line 304 304: def slice(*args) 305: if args.size > 2 306: raise ArgumentError, "wrong number of arguments (#{args.size} for 1)" # Do as if we were native 307: elsif (args.size == 2 && !(args.first.is_a?(Numeric) || args.first.is_a?(Regexp))) 308: raise TypeError, "cannot convert #{args.first.class} into Integer" # Do as if we were native 309: elsif (args.size == 2 && !args[1].is_a?(Numeric)) 310: raise TypeError, "cannot convert #{args[1].class} into Integer" # Do as if we were native 311: elsif args[0].kind_of? Range 312: cps = Unicode.u_unpack(@wrapped_string).slice(*args) 313: result = cps.nil? ? nil : cps.pack('U*') 314: elsif args[0].kind_of? Regexp 315: result = @wrapped_string.slice(*args) 316: elsif args.size == 1 && args[0].kind_of?(Numeric) 317: character = Unicode.u_unpack(@wrapped_string)[args[0]] 318: result = character && [character].pack('U') 319: else 320: cps = Unicode.u_unpack(@wrapped_string).slice(*args) 321: result = cps && cps.pack('U*') 322: end 323: result && chars(result) 324: 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/mail/multibyte/chars.rb, line 247 247: def split(*args) 248: @wrapped_string.split(*args).map { |i| i.mb_chars } 249: end
Strips entire range of Unicode whitespace from the right and left of the string.
# File lib/mail/multibyte/chars.rb, line 185 185: def strip 186: rstrip.lstrip 187: 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/mail/multibyte/chars.rb, line 411 411: def tidy_bytes(force = false) 412: chars(Unicode.tidy_bytes(@wrapped_string, force)) 413: 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/mail/multibyte/chars.rb, line 366 366: def titleize 367: chars(downcase.to_s.gsub(/\b('?[\S])/) { Unicode.apply_mapping $1, :uppercase_mapping }) 368: 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/mail/multibyte/chars.rb, line 341 341: def upcase 342: chars(Unicode.apply_mapping(@wrapped_string), :uppercase_mapping) 343: end
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