Yes, it works with composer.

I have bought the block. But when adding it to composer and creating a page I get the following error:
"count(): Parameter must be an array or an object that implements Countable".

What is your server php version?

7.2.6

# concrete5 Version
Core Version - 8.4.0
Version Installed - 8.4.0
Database Version - 20180524000000

# concrete5 Packages
Automatic Email Obfuscator (2.0.1), Block Designer (3.1.3), Block Designer Pro (3.0.0), ExchangeCore reCAPTCHA (1.1.1), Grand Gallery (1.0.0), Open Graph Tags Lite (2.1.3), Social Share Lite (2.1.3)

# concrete5 Cache Settings
Block Cache - Off
Overrides Cache - Off
Full Page Caching - Off
Full Page Cache Lifetime - Every 6 hours (default setting).

# Server Software
Apache/2

# Server API
fpm-fcgi

# PHP Version
7.2.6

# PHP Extensions
bcmath, calendar, cgi-fcgi, Core, ctype, curl, date, dom, fileinfo, filter, ftp, gd, gettext, hash, iconv, intl, json, libxml, mbstring, mysqli, mysqlnd, openssl, pcre, PDO, pdo_mysql, pdo_sqlite, Phar, posix, Reflection, session, SimpleXML, soap, sockets, SPL, sqlite3, standard, tokenizer, xml, xmlreader, xmlwriter, xsl, zip, zlib

# PHP Settings
max_execution_time - 30
log_errors_max_len - 1024
max_file_uploads - 20
max_input_nesting_level - 64
max_input_time - 60
max_input_vars - 1000
memory_limit - 128M
post_max_size - 64M
upload_max_filesize - 64M
mysqli.max_links - Unlimited
mysqli.max_persistent - Unlimited
pcre.backtrack_limit - 1000000
pcre.recursion_limit - 100000
session.cache_limiter - <i>no value</i>
session.gc_maxlifetime - 7200
soap.wsdl_cache_limit - 5

There were some problems with concrete5 working with php 7.2 lately.
I will look if I can fix it (or if it is framework problem).
Temporarily you can just lower your php version to 7.0 or 7.1.

This bug should be fixed in version 1.0.1, which is available on marketplace now.

Thank you for your quick response, works great.