文字数字混合处理（数字小）

// @param text 如：h2o2 co2 
// @param size 角标数字字体size
+(NSMutableAttributedString*)getNumberSubscriptString:(NSString*)text size:(CGFloat)size{
    if (text.length == 0) {
        return nil;
    }
    NSMutableArray *numTmpArray = [NSMutableArray array];
    NSMutableAttributedString *resAttributed = [[NSMutableAttributedString alloc]initWithString:text.uppercaseString];
    
    NSScanner *scanner = [NSScanner scannerWithString:text];
    NSCharacterSet *numbers = [NSCharacterSet characterSetWithCharactersInString:@"0123456789"];
    
    while (![scanner isAtEnd]) {
        [scanner scanUpToCharactersFromSet:numbers intoString:NULL];
        int number;
        [scanner scanInt:&number];
        
        NSString *num=[NSString stringWithFormat:@"%ld",number];
        [numTmpArray addObject:num];
    }
    
    if (numTmpArray.count) {
        NSRange range = NSMakeRange(0, 0);
        for (int i = 0; i < numTmpArray.count; i++) {
            range = [text rangeOfString:numTmpArray[i]];
            [resAttributed addAttribute:NSFontAttributeName value:[UIFont systemFontOfSize:size] range:range];
        }
    }else{
        [resAttributed addAttribute:NSFontAttributeName value:[UIFont systemFontOfSize:size] range:NSMakeRange(0, text.length)];
    }
    return resAttributed;
}