Ruby 1.9 new features: All about encoding

The biggest change in Ruby 1.9 is the all about encoding. First, Encoding class had been created to deal encode information. If you see the all encodings in your Ruby environment, see the output of Encoding

> /opt/ruby-1.9.1/bin/irb
irb(main):001:0> RUBY_VERSION              
=> "1.9.1"                                 
irb(main):002:0> Encoding.constants.find_all{|const|Encoding.const_get(const).is_a?(Encoding)}
=> [:ASCII_8BIT, :Big5, :BIG5, :CP949, :Emacs_Mule, :EMACS_MULE, :EUC_JP, :EUC_KR, :EUC_TW, :GB18030, :GBK, :ISO_8859_1, :ISO_8859_2, :ISO_8859_3, :ISO_8859_4,:ISO_8859_5, :ISO_8859_6, :ISO_8859_7, :ISO_8859_8, :ISO_8859_9, :ISO_8859_10, :ISO_8859_11, :ISO_8859_13, :ISO_8859_14, :ISO_8859_15, :ISO_8859_16, :KOI8_R, :KOI8_U, :Shift_JIS, :SHIFT_JIS, :US_ASCII, :UTF_8, :UTF_16BE, :UTF_16LE, :UTF_32BE, :UTF_32LE, :Windows_1251, :WINDOWS_1251, :BINARY, :IBM437, :CP437, :IBM737, :CP737, :IBM775, :CP775, :CP850, :IBM850, :IBM852, :CP852, :IBM855, :CP855, :IBM857, :CP857, :IBM860, :CP860, :IBM861, :CP861, :IBM862, :CP862, :IBM863, :CP863,:IBM864, :CP864, :IBM865, :CP865, :IBM866, :CP866, :IBM869, :CP869, :Windows_1258, :WINDOWS_1258, :CP1258, :GB1988, :MacCentEuro, :MACCENTEURO, :MacCroatian, :MACCROATIAN, :MacCyrillic, :MACCYRILLIC, :MacGreek, :MACGREEK, :MacIceland, :MACICELAND, :MacRoman, :MACROMAN, :MacRomania, :MACROMANIA, :MacThai, :MACTHAI, :MacTurkish, :MACTURKISH, :MacUkraine, :MACUKRAINE, :CP950, :Stateless_ISO_2022_JP,:STATELESS_ISO_2022_JP, :EucJP, :EUCJP, :EucJP_ms, :EUCJP_MS, :EUC_JP_MS, :CP51932, :EucKR, :EUCKR, :EucTW, :EUCTW, :EUC_CN, :EucCN, :EUCCN, :GB12345, :CP936, :ISO_2022_JP, :ISO2022_JP, :ISO_2022_JP_2, :ISO2022_JP2, :ISO8859_1, :Windows_1252, :WINDOWS_1252, :CP1252, :ISO8859_2, :Windows_1250, :WINDOWS_1250, :CP1250, :ISO8859_3, :ISO8859_4, :ISO8859_5, :ISO8859_6, :Windows_1256, :WINDOWS_1256, :CP1256, :ISO8859_7, :Windows_1253, :WINDOWS_1253, :CP1253, :ISO8859_8, :Windows_1255, :WINDOWS_1255, :CP1255, :ISO8859_9, :Windows_1254, :WINDOWS_1254, :CP1254, :ISO8859_10, :ISO8859_11, :TIS_620, :Windows_874, :WINDOWS_874, :CP874, :ISO8859_13, :Windows_1257, :WINDOWS_1257, :CP1257, :ISO8859_14, :ISO8859_15, :ISO8859_16, :CP878, :SJIS, :Windows_31J, :WINDOWS_31J, :CP932, :CsWindows31J, :CSWINDOWS31J, :MacJapanese, :MACJAPANESE, :MacJapan, :MACJAPAN, :ASCII, :ANSI_X3_4_1968, :UTF_7, :CP65000, :CP65001, :UTF8_MAC, :UTF_8_MAC, :UCS_2BE, :UCS_4BE, :UCS_4LE, :CP1251]

Second, String class has 3 methods that have similar names and similar behaviors: force_encoding, encode! and encode. See the what these are different from.

irb(main):003:0> a0, b0, c0 = 'ü', 'ü', 'ü'
=> ["ü", "ü", "ü"]
irb(main):004:0> [a0, b0, c0].collect(&:encoding)
=> [#<Encoding:UTF-8>, #<Encoding:UTF-8>, #<Encoding:UTF-8>]
irb(main):005:0> a1 = a0.force_encoding(Encoding::EUC_JP)
=> "ü"
irb(main):006:0> b1 = b0.encode!(Encoding::EUC_JP)
=> "���"
irb(main):007:0> c1 = c0.encode(Encoding::EUC_JP)
=> "���"
irb(main):008:0> [a1, b1, c1].collect(&:encoding)
=> [#<Encoding:EUC-JP>, #<Encoding:EUC-JP>, #<Encoding:EUC-JP>]
irb(main):009:0> a0
=> "ü"
irb(main):010:0> b0
=> "���"
irb(main):011:0> c0
=> "ü"
irb(main):012:0> [a0, b0, c0].collect(&:encoding)
=> [#<Encoding:EUC-JP>, #<Encoding:EUC-JP>, #<Encoding:UTF-8>]
irb(main):013:0> a2, b2, c2 = [a1, b1, c1].collect{|str| str.encode(Encoding::UTF_8)}
=> ["端", "ü", "ü"]
irb(main):014:0> [a2, b2, c2].collect(&:encoding)
=> [#<Encoding:UTF-8>, #<Encoding:UTF-8>, #<Encoding:UTF-8>]

force_encoding and encode! are destructive method.