Functionaly pure message passing

[mjadczak]

@Crowdhailer

In my opinion the module using GenServer is already the business logic module. With Genserver hiding details about sending monitoring etc.

I would agree that in most cases, that is sufficient. If there were a very complex business process, however, which may require a lot of complex rules about sending multiple replies or deferring some replies, it could be beneficial to write a separate pure module with business logic, which would provide in a pure, declarative form “instructions” for the GenServer to carry out, facilitating better testing of that complex logic. However, most GenServer implementations will not need that complexity.