1.编码 :
NSStringEncoding enc = CFStringConvertEncodingToNSStringEncoding (kCFStringEncodingGB_18030_2000);
//GB2312,GBK
NSISOLatin1StringEncoding
NSUTF8StringEncoding等
2.截取字符串
substringWithRange substringToIndex:<#(NSUInteger)#> substringFromIndex:<#(NSUInteger)#>
3.分割字符为NSArray数组
componentsSeparatedByString:<#(NSString *)#>
4.替换字符
stringByReplacingOccurrencesOfString