1、中文转拼音

+ (NSString *)firstCharactor:(NSString *)aString
{
    if (aString.isNoEmpty) {
        //转成了可变字符串
        NSMutableString *str = [NSMutableString stringWithString:aString];
        //先转换为带声调的拼音
        CFStringTransform((CFMutableStringRef)str,NULL, kCFStringTransformMandarinLatin,NO);
        //再转换为不带声调的拼音
        CFStringTransform((CFMutableStringRef)str,NULL, kCFStringTransformStripDiacritics,NO);
        //转化为大写拼音
        //    NSString *pinYin = [str capitalizedString];
        //获取并返回首字母
        //    return [pinYin substringToIndex:1];
        return str;
    }
    return aString;
}

//判断是否为空，处理服务器返回多种多样空类型的情况
- (BOOL)isNoEmpty
{
    if ([self isKindOfClass:[NSNull class]])
    {
        return NO;
    }
    else if ([self isKindOfClass:[NSString class]])
    {
        NSString *str = (NSString *)self;
        return [str length] > 0;
    }
    else if ([self isKindOfClass:[NSData class]])
    {
        
        return [(NSData *)self length] > 0;
    }
    else if ([self isKindOfClass:[NSArray class]])
    {
        
        return [(NSArray *)self count] > 0;
    }
    else if ([self isKindOfClass:[NSDictionary class]])
    {
        
        return [(NSDictionary *)self count] > 0;
    }
    
    return YES;
}

2、MD5

- (NSString*)md5
{
    const char *cStr=[self UTF8String];
    unsigned char result[CC_MD5_DIGEST_LENGTH];
    CC_MD5(cStr,(CC_LONG)strlen(cStr), result);
    return [NSString stringWithFormat:
            @"%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x",
            result[0], result[1], result[2], result[3],
            result[4], result[5], result[6], result[7],
            result[8], result[9], result[10], result[11],
            result[12], result[13], result[14], result[15]
            ];
}

3、去掉字符串中的空格

- (NSString *)trimString
{
    // 截断字符串中的所有空白字符（空格,\t,\n,\r）
    return [self stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
}