NSString对应的编码格式，查询NSStringEncoding
NSStringEncoding enc = CFStringConvertEncodingToNSStringEncoding (kCFStringEncodingGB_18030_2000); //GB2312,GBK
创建一个mac os的工程，加入代码：
const NSStringEncoding *encodings = [NSString availableStringEncodings];
NSMutableString *str = [[NSMutableString alloc] init];
NSStringEncoding encoding;
while ((encoding = *encodings++) != 0)
{
[str appendFormat: @"%@ === %li\n", [NSString localizedNameOfStringEncoding:encoding], encoding];
}
NSLog(@"%@",str);得到：
Western (Mac OS Roman) === 30
Japanese (Mac OS) === 2147483649
Traditional Chinese (Mac OS) === 2147483650
Korean (Mac OS) === 2147483651
Arabic (Mac OS) === 2147483652
Hebrew (Mac OS) === 2147483653
Greek (Mac OS) === 2147483654
Cyrillic (Mac OS) === 2147483655
Devanagari (Mac OS) === 2147483657
Gurmukhi (Mac OS) === 2147483658
Gujarati (Mac OS) === 2147483659
Thai (Mac OS) === 2147483669
Simplified Chinese (Mac OS) === 2147483673
Tibetan (Mac OS) === 2147483674
Central European (Mac OS) === 2147483677
Symbol (Mac OS) === 6
Dingbats (Mac OS) === 2147483682
Turkish (Mac OS) === 2147483683
Croatian (Mac OS) === 2147483684
Icelandic (Mac OS) === 2147483685
Romanian (Mac OS) === 2147483686
Celtic (Mac OS) === 2147483687
Gaelic (Mac OS) === 2147483688
Keyboard Symbols (Mac OS) === 2147483689
Farsi (Mac OS) === 2147483788
Cyrillic (Mac OS Ukrainian) === 2147483800
Inuit (Mac OS) === 2147483884
Unicode (UTF-16) === 10
Unicode (UTF-7) === 2214592768
Unicode (UTF-8) === 4
Unicode (UTF-32) === 2348810496
Unicode (UTF-16BE) === 2415919360
Unicode (UTF-16LE) === 2483028224
Unicode (UTF-32BE) === 2550137088
Unicode (UTF-32LE) === 2617245952
Western (ISO Latin 1) === 5
Central European (ISO Latin 2) === 9
Western (ISO Latin 3) === 2147484163
Central European (ISO Latin 4) === 2147484164
Cyrillic (ISO 8859-5) === 2147484165
Arabic (ISO 8859-6) === 2147484166
Greek (ISO 8859-7) === 2147484167
Hebrew (ISO 8859-8) === 2147484168
Turkish (ISO Latin 5) === 2147484169
Nordic (ISO Latin 6) === 2147484170
Thai (ISO 8859-11) === 2147484171
Baltic (ISO Latin 7) === 2147484173
Celtic (ISO Latin 8) === 2147484174
Western (ISO Latin 9) === 2147484175
Romanian (ISO Latin 10) === 2147484176
Latin-US (DOS) === 2147484672
Greek (DOS) === 2147484677
Baltic (DOS) === 2147484678
Western (DOS Latin 1) === 2147484688
Greek (DOS Greek 1) === 2147484689
Central European (DOS Latin 2) === 2147484690
Cyrillic (DOS) === 2147484691
Turkish (DOS) === 2147484692
Portuguese (DOS) === 2147484693
Icelandic (DOS) === 2147484694
Hebrew (DOS) === 2147484695
Canadian French (DOS) === 2147484696
Arabic (DOS) === 2147484697
Nordic (DOS) === 2147484698
Russian (DOS) === 2147484699
Greek (DOS Greek 2) === 2147484700
Thai (Windows, DOS) === 2147484701
Japanese (Windows, DOS) === 8
Simplified Chinese (Windows, DOS) === 2147484705
Korean (Windows, DOS) === 2147484706
Traditional Chinese (Windows, DOS) === 2147484707
Western (Windows Latin 1) === 12
Central European (Windows Latin 2) === 15
Cyrillic (Windows) === 11
Greek (Windows) === 13
Turkish (Windows Latin 5) === 14
Hebrew (Windows) === 2147484933
Arabic (Windows) === 2147484934
Baltic (Windows) === 2147484935
Vietnamese (Windows) === 2147484936
Western (ASCII) === 1
Japanese (Shift JIS X0213) === 2147485224
Chinese (GBK) === 2147485233
Chinese (GB 18030) === 2147485234
Japanese (ISO 2022-JP) === 21
Japanese (ISO 2022-JP-2) === 2147485729
Japanese (ISO 2022-JP-1) === 2147485730
Chinese (ISO 2022-CN) === 2147485744
Korean (ISO 2022-KR) === 2147485760
Japanese (EUC) === 3
Simplified Chinese (GB 2312) === 2147486000
Traditional Chinese (EUC) === 2147486001
Korean (EUC) === 2147486016
Japanese (Shift JIS) === 2147486209
Cyrillic (KOI8-R) === 2147486210
Traditional Chinese (Big 5) === 2147486211
Western (Mac Mail) === 2147486212
Simplified Chinese (HZ GB 2312) === 2147486213
Traditional Chinese (Big 5 HKSCS) === 2147486214
Ukrainian (KOI8-U) === 2147486216
Traditional Chinese (Big 5-E) === 2147486217
Western (NextStep) === 2
Non-lossy ASCII === 7
Western (EBCDIC Latin Core) === 2147486721
Western (EBCDIC Latin 1) === 2147486722
得到这么多神奇的数字，这些神奇的数字就是对应的编码格式。
---------------------------分割线-----------------------
得到的是有符号的long类型：
const NSStringEncoding *encodings = [NSString availableStringEncodings];
NSMutableString *str = [[NSMutableString alloc] init];
NSStringEncoding encoding;
while ((encoding = *encodings++) != 0)
{
[str appendFormat: @"%@ === %i\n", [NSString localizedNameOfStringEncoding:encoding], encoding];
}
NSLog(@"%@",str);
下面是mac os的格式代码：
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