Is it possible to 'nest' sendable objects?

[dawonn]

InitSendable(frc::SendableBuilder &builder) {} is my new favorite thing, but is it possible to 'nest' sendable objects?

I guess I expected to see is a builder.AddSendable() function that would let me nest subsystems within other systems. Is this possible?

[dawonn]

I was able to more-or-less achieve the desired effect, but I'm still curious if there is a better / 'correct' way since each sub object does not have the .type specified an all I really did was add all of the properties of the child objects to the parent.

drivebase.cpp

void Drivetrain::InitSendable(frc::SendableBuilder &builder)
{
  // Modules
  m_frontLeft.InitSendable(builder, "FL");
  m_frontRight.InitSendable(builder, "FR");
  m_backLeft.InitSendable(builder, "BL");
  m_backRight.InitSendable(builder, "BR");

  builder.SetSmartDashboardType("DriveBase");
  builder.SetActuator(true);
}

SwerveModule.cpp

void SwerveModule::InitSendable(frc::SendableBuilder &builder)
{
  InitSendable(builder, "");
}

void SwerveModule::InitSendable(frc::SendableBuilder &builder, std::string name)
{
  builder.SetSmartDashboardType("SwerveModule");
  builder.SetActuator(true);

  // Prefix for nested objects
  if(name != "") name += "/";

  // Drive Control
  builder.AddDoubleProperty(
      name + "Drive kP", [this] { return m_drivePIDController.GetP(); }, [this](double value) { m_drivePIDController.SetP(value); });
  // etc...
}

The child objects collapse in the NT tree as desired:

[auscompgeek]

You probably want SendableRegistry::AddChild and/or SendableRegistry::SetSubsystem.

[dawonn]

neat! AddChild looked promising and i tried a couple things but I'm not sure how it is supposed to work. I looked at the MecanumDrive Class as an example.

It appear that this snippet should add the four speed controllers as child objects, but that does not appear to be the case. As a matter of fact, they added explicit properties for these in the MechanumDrive InitSendable function.

I expected to see each of the speed controllers show up as children in the network table tree. What am I missing?