Last things first this time. Between part 38 and this part the relevant changes are:
Eventclass and its subclass into a separate file;
There is no new functionality, but enough can go wrong between the last installment and this one that I want to provide a separate set of notes.
Commands you might ever need and define them now, both because it feels responsible and plan-ahead-y and because it can feel silly to define an empty class meant to be subclassed and then only provide one subclass. If there are some you know you'll need, go ahead. But it's easy to go wrong (and spend time inefficiently) if you guess in advance at what you'll need. Having
Commandin place is more than enough planning. With this structure in place, we're not going to have a hard time adding any necessary items later. Further planning now therefore gains us no safety.
KickoffCoordinators somehow. (I'm not sold on the name: whatever it is in virtue of which my watering the plants means that I need to do it again after a while, that's what we're talking about.) It's tempting to create an extra field in the
taskSQL table and put that information there. I think this would be a serious mistake. The whole purpose of distinguishing between the coordinator and the task is that they're different things. That probably means they need different database tables to be persisted accurately. And adding several extra columns to the
tasktable is a heavy cost in complexity.
coordinatortable correspondingly. I think this is a mistake, too. If other coordinators are way more complex, we can define other SQL database tables (or even persistence mechanisms that are not SQL database tables) for them. That can all be handled at the repository level. It's no problem to have a table structured just for (what I've called)
Finally, the advanced mechanics of message-passing systems is a deep topic (easily enough to spend a career studying and specializing in). This, by contrast, is intended as enough infrastructure to allow us to build a clean system at modest scale (or perhaps just for personal use). I won't (at least for the next few hundred or so installments) be worried about: