Thanks a lot for sharing. A tiny error to be fixed though, I think: you mention everywhere filename: "invoice-#{date}" but the variable date has never been defined.

Thank you so much for sharing such useful tips. One point: you have a tiny typo in Comapny.find_by!(name:...), - it should be Company, I suppose :). Also in the Brake#do_brake method, I don't think the call puts "Brake id: #{self.brake.id}" to correct, - you are calling brake on the instance of the Brake class instead of just calling id method.

AbulAsar S., no worries, by the way, the code in the repo contains the correct version :).

Error in the template: <i><%= full_name({title.user}) %></i>. It should be task.user instead; Error when calling Project.change_task_state(taskId, target). It should be Organization.change_task_state(taskId, target)

You mentioned: "We are going to place both functions in a separate module organization.ex under trello_app/lib/trello_app folder." I suppose it to be in trello_app/lib folder because: The name of the created module you were displaying later was defmodule TrelloApp.Organization you asked to alias it as TrelloApp.Organization later in the iex session.