//找到数字在字符串中得位置
 [[self numberArray] enumerateObjectsUsingBlock:^(id  _Nonnull obj, NSUInteger idx, BOOL * _Nonnull stop) {
        NSString *tmpStr = @"现在开始拍车了！今日总共拍品1200辆，有您的心愿车56辆，赶紧去看看";;
        NSRange range = [tmpStr rangeOfString:obj];
        if (range.location != NSNotFound)
        {
            NSLog(@"found at location = %lu, length = %lu",(unsigned long)range.location,(unsigned long)range.length);
            NSLog(@"%@",obj);
        }
        else
        {
            NSLog(@"Not Found");
        }
    }];

//获取字符串中所有数字字符串
-(NSMutableArray *)numberArray
{
    NSString *originalString = @"现在开始拍车了！今日总共拍品1200辆，有您的心愿车56辆，赶紧去看看";;
    
    
    NSMutableArray  *array = [NSMutableArray array];

    NSString *tempStr;
    
    NSScanner *scanner = [NSScanner scannerWithString:originalString];
    
    NSCharacterSet *numbers = [NSCharacterSet characterSetWithCharactersInString:@"0123456789"];
    
    while (![scanner isAtEnd])
    {
        [scanner scanUpToCharactersFromSet:numbers intoString:NULL];
        
        [scanner scanCharactersFromSet:numbers intoString:&tempStr];
        
        if (tempStr&& tempStr.length > 0)
        {
            [array addObject:tempStr];
        }
        tempStr = @"";
    }
    return array;
}

生成32位随机由字母和数字组成的字符串

//生成32位随机由字母和数字组成的字符串
- (NSString *)creat32randomString
{
    char data[32];
    
    for (int i=0; i < 32; i ++)
    {
        char c = (char)('A' + (arc4random_uniform(26)));
        char b = (char)('a' + (arc4random_uniform(26)));
        char a = (char)('0' + (arc4random_uniform(10)));
        
        char ch[3] = {c ,b, a};
        
        int index = arc4random() % 3;
        
        data[i] = ch[index];
    }
    return [[NSString alloc] initWithBytes:data
                                    length:32
                                  encoding:NSUTF8StringEncoding];
    
}

打印结果：
2016-12-07 15:30:28.365 HHAnimations[26877:618657] found at location = 14, length = 4
2016-12-07 15:30:28.944 HHAnimations[26877:618657] 1200
2016-12-07 15:30:33.356 HHAnimations[26877:618657] found at location = 26, length = 2
2016-12-07 15:30:33.357 HHAnimations[26877:618657] 56