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allwpilib/wpilibc/src/main/native/include/frc2/command/Subsystem.h

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3.5 KiB
C++

/*----------------------------------------------------------------------------*/
/* Copyright (c) 2019 FIRST. All Rights Reserved. */
/* Open Source Software - may be modified and shared by FRC teams. The code */
/* must be accompanied by the FIRST BSD license file in the root directory of */
/* the project. */
/*----------------------------------------------------------------------------*/
#pragma once
#include <frc2/command/CommandScheduler.h>
#include <utility>
namespace frc2 {
class Command;
/**
* A robot subsystem. Subsystems are the basic unit of robot organization in
* the Command-based framework; they encapsulate low-level hardware objects
* (motor controllers, sensors, etc) and provide methods through which they can
* be used by Commands. Subsystems are used by the CommandScheduler's resource
* management system to ensure multiple robot actions are not "fighting" over
* the same hardware; Commands that use a subsystem should include that
* subsystem in their GetRequirements() method, and resources used within a
* subsystem should generally remain encapsulated and not be shared by other
* parts of the robot.
*
* <p>Subsystems must be registered with the scheduler with the
* CommandScheduler.RegisterSubsystem() method in order for the
* Periodic() method to be called. It is recommended that this method be called
* from the constructor of users' Subsystem implementations. The
* SubsystemBase class offers a simple base for user implementations
* that handles this.
*
* @see Command
* @see CommandScheduler
* @see SubsystemBase
*/
class Subsystem {
public:
~Subsystem();
/**
* This method is called periodically by the CommandScheduler. Useful for
* updating subsystem-specific state that you don't want to offload to a
* Command. Teams should try to be consistent within their own codebases
* about which responsibilities will be handled by Commands, and which will be
* handled here.
*/
virtual void Periodic();
/**
* Sets the default Command of the subsystem. The default command will be
* automatically scheduled when no other commands are scheduled that require
* the subsystem. Default commands should generally not end on their own, i.e.
* their IsFinished() method should always return false. Will automatically
* register this subsystem with the CommandScheduler.
*
* @param defaultCommand the default command to associate with this subsystem
*/
template <class T, typename = std::enable_if_t<std::is_base_of_v<
Command, std::remove_reference_t<T>>>>
void SetDefaultCommand(T&& defaultCommand) {
CommandScheduler::GetInstance().SetDefaultCommand(
this, std::forward<T>(defaultCommand));
}
/**
* Gets the default command for this subsystem. Returns null if no default
* command is currently associated with the subsystem.
*
* @return the default command associated with this subsystem
*/
Command* GetDefaultCommand() const;
/**
* Returns the command currently running on this subsystem. Returns null if
* no command is currently scheduled that requires this subsystem.
*
* @return the scheduled command currently requiring this subsystem
*/
Command* GetCurrentCommand() const;
/**
* Registers this subsystem with the CommandScheduler, allowing its
* Periodic() method to be called when the scheduler runs.
*/
void Register();
};
} // namespace frc2