最近再開發ios程式的時候，發現從url取得的utf8編碼資料中文部分顯示為亂碼，為此在網上查詢了一些資料，對nsstring的編碼問題做一下總結：
幫助文件列出的nsstring支援的編碼：
enum ;
列表中很多編碼都沒有，原來這個列表沒有把全部的編碼列出來，通過以下**可以列出nsstring支援的全部編碼：
執行結果：
western (mac os roman) = 30
japanese (mac os) = -2147483647
traditional chinese (mac os) = -2147483646
korean (mac os) = -2147483645
arabic (mac os) = -2147483644
hebrew (mac os) = -2147483643
greek (mac os) = -2147483642
cyrillic (mac os) = -2147483641
devanagari (mac os) = -2147483639
gurmukhi (mac os) = -2147483638
gujarati (mac os) = -2147483637
thai (mac os) = -2147483627
simplified chinese (mac os) = -2147483623
tibetan (mac os) = -2147483622
central european (mac os) = -2147483619
symbol (mac os) = 6
dingbats (mac os) = -2147483614
turkish (mac os) = -2147483613
croatian (mac os) = -2147483612
icelandic (mac os) = -2147483611
romanian (mac os) = -2147483610
celtic (mac os) = -2147483609
gaelic (mac os) = -2147483608
keyboard symbols (mac os) = -2147483607
farsi (mac os) = -2147483508
cyrillic (mac os ukrainian) = -2147483496
inuit (mac os) = -2147483412
unicode (utf-16) = 10
unicode (utf-7) = -2080374528
unicode (utf-8) = 4
unicode (utf-32) = -1946156800
unicode (utf-16be) = -1879047936
unicode (utf-16le) = -1811939072
unicode (utf-32be) = -1744830208
unicode (utf-32le) = -1677721344
western (iso latin 1) = 5
central european (iso latin 2) = 9
western (iso latin 3) = -2147483133
central european (iso latin 4) = -2147483132
cyrillic (iso 8859-5) = -2147483131
arabic (iso 8859-6) = -2147483130
greek (iso 8859-7) = -2147483129
hebrew (iso 8859-8) = -2147483128
turkish (iso latin 5) = -2147483127
nordic (iso latin 6) = -2147483126
thai (iso 8859-11) = -2147483125
baltic (iso latin 7) = -2147483123
celtic (iso latin 8) = -2147483122
western (iso latin 9) = -2147483121
romanian (iso latin 10) = -2147483120
latin-us (dos) = -2147482624
greek (dos) = -2147482619
baltic (dos) = -2147482618
western (dos latin 1) = -2147482608
greek (dos greek 1) = -2147482607
central european (dos latin 2) = -2147482606
cyrillic (dos) = -2147482605
turkish (dos) = -2147482604
portuguese (dos) = -2147482603
icelandic (dos) = -2147482602
hebrew (dos) = -2147482601
canadian french (dos) = -2147482600
arabic (dos) = -2147482599
nordic (dos) = -2147482598
russian (dos) = -2147482597
greek (dos greek 2) = -2147482596
thai (windows, dos) = -2147482595
japanese (windows, dos) = 8
simplified chinese (windows, dos) = -2147482591
korean (windows, dos) = -2147482590
traditional chinese (windows, dos) = -2147482589
western (windows latin 1) = 12
central european (windows latin 2) = 15
cyrillic (windows) = 11
greek (windows) = 13
turkish (windows latin 5) = 14
hebrew (windows) = -2147482363
arabic (windows) = -2147482362
baltic (windows) = -2147482361
vietnamese (windows) = -2147482360
western (ascii) = 1
japanese (shift jis x0213) = -2147482072
chinese (gbk) = -2147482063
chinese (gb 18030) = -2147482062
japanese (iso 2022-jp) = 21
japanese (iso 2022-jp-2) = -2147481567
japanese (iso 2022-jp-1) = -2147481566
chinese (iso 2022-cn) = -2147481552
korean (iso 2022-kr) = -2147481536
japanese (euc) = 3
simplified chinese (gb 2312) = -2147481296
traditional chinese (euc) = -2147481295
korean (euc) = -2147481280
japanese (shift jis) = -2147481087
cyrillic (koi8-r) = -2147481086
traditional chinese (big 5) = -2147481085
western (mac mail) = -2147481084
simplified chinese (hz gb 2312) = -2147481083
traditional chinese (big 5 hkscs) = -2147481082
ukrainian (koi8-u) = -2147481080
traditional chinese (big 5-e) = -2147481079
western (nextstep) = 2
non-lossy ascii = 7
western (ebcdic latin core) = -2147480575
western (ebcdic latin 1) = -2147480574
從結果中可以看到：
unicode (utf-8) = 4 utf8編碼4
所以，從url取得utf編碼的資料時，可以這樣處理：
最後列印出的中文顯示正常了。
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