unicode与utf8编码相互转化

- (NSString *) packUtf8ToUnicode:(NSString *)string
{
    NSUInteger length = [string length];
    NSMutableString *s = [NSMutableString stringWithCapacity:0];
    for (int i = 0;i < length; i++) {
        unichar _char = [string characterAtIndex:i];
        if (_char <= '9' && _char >= '0') {
            [s appendFormat:@"%@",[string substringWithRange:NSMakeRange(i, 1)]];
        }else if(_char >= 'a' && _char <= 'z')
        {
            [s appendFormat:@"%@",[string substringWithRange:NSMakeRange(i, 1)]];
        }else if(_char >= 'A' && _char <= 'Z')
        {
            [s appendFormat:@"%@",[string substringWithRange:NSMakeRange(i, 1)]];
        }else
        {
            [s appendFormat:@"\\u%x",[string characterAtIndex:i]];
        }

    }
    return s;
}

- (NSString *)unPackUnicode:(NSString *)unicodeStr {
    NSString *tempStr1 = [unicodeStr stringByReplacingOccurrencesOfString:@"\\u" withString:@"\\U"];
    NSString *tempStr2 = [tempStr1 stringByReplacingOccurrencesOfString:@"\"" withString:@"\\\""];
    NSString *tempStr3 = [[@"\"" stringByAppendingString:tempStr2] stringByAppendingString:@"\""];
    NSData *tempData = [tempStr3 dataUsingEncoding:NSUTF8StringEncoding];
    NSString* returnStr = [NSPropertyListSerialization propertyListFromData:tempData
                                                           mutabilityOption:NSPropertyListImmutable
                                                                     format:NULL
                                                           errorDescription:NULL];
    
    return [returnStr stringByReplacingOccurrencesOfString:@"\\r\\n" withString:@"\n"];
}