This chapter adds an OTP application to the demo.
This is the first chapter where I have found some typos
info_sys/application.ex needs the following to work:
alias InfoSys.Counter
Without that the app won’t start.
You also need to be careful with the examples. The name of the files are sometimes incorrect (although the listed path is right). Sometimes it asks you to edit a file in Rumbl when it actually means InfoSys.
There are also a lot of mistakes in the supervisor demos. Sometimes aliases are missed (as above) and sometimes it refers to the wrong project.
Developer Rants 