How to handle sub-instancing?

[GitMoDu]

Since the Process constructor requires the scheduler reference, how can I add a process to the scheduler inside the a custom Process class? The Arduino C/++ limitations are kind of hard on these issues.

[wizard97]

If the parent process already knows the child processes it needs during construction, you should should create the child process during the parents process' construction. This will avoid the use of heap memory, which is preferred for embedded platforms with no mmu. You will need to use an initialization list by passing in the Scheduler reference argument.

If you must dynamically allocate new processes (aka using the new keyword), you can get the reference you need with just by calling scheduler():

inline Scheduler &scheduler() { return _scheduler; }

[GitMoDu]

Thank you, yes, I don't want to use Heap, so getting the constructors right is hard.

"If the parent process already knows the child processes it needs during construction"
Yes, this is the use case I'd like to explore. The simplest I could do now is:

Scheduller ProcessScheduller;
ProcessSub Sub(ProcessScheduller, PRIORITY, PERIOD);
ProcessMain Main(ProcessScheduller, PRIORITY, PERIOD, Sub); //Sub process is passed as argument for reference.

What I would like to do is something like:

ProcessMain : Process
{
    ProcessSub Sub;

    ProcessMain(scheduller, PRIORITY, PERIOD) : Sub(&scheduller,PRIORITY,PERIOD);
}
Scheduller ProcessScheduller;
ProcessMain Main(ProcessScheduller, PRIORITY, PERIOD); 

This obviously doesn't work, but it's the general idea. Can the scheduller reference be passed along in the constructor to build sub processes?

Alternatively, could we have instances of projects where we only "attach" them to the scheduler on run-time (Setup(Scheduler)) without allocating heap memory?

[wizard97]

Yeah, that's correct you can just directly pass the same reference in. You're very close:

You use the initialization list in your .cpp, it should look something like this:

ProcessMain(scheduller, PRIORITY, PERIOD) : Sub(scheduller,PRIORITY,PERIOD)
{
// Parents constructor implementation here
}

[GitMoDu]

I'll try it and report, but last time I tried something similar, it refused to compile.

[wizard97]

Alternatively, could we have instances of projects where we only "attach" them to the scheduler on run-time (Setup(Scheduler)) without allocating heap memory?

The problem with that approach is the way it is designed is the user never should manually need to call setup as the scheduler calls it automatically when needed. It's not even possible either because setup is a protected method. Also, this would force the use of scheduler pointers instead of references which are more prone to errors the compiler won't complain about.

[GitMoDu]

SORCERY!!! It compiles! :D I'm surprised I could just declare a Process with empty constructor.

Guess it's time to ditch my custom micro-service implementation and just stack a few low-priority processes on the scheduler. I'll add an example of such usage, on a pull request, as a thank you.

[wizard97]

I'm glad you got child processes working, there definitely need to be a ton more examples. I have just been too lazy to do them myself...

Let me know if you have any more issues.
Aaron

[GitMoDu]

As promised, I've requested a pull of the sub-instancing example.