frc2::Subsystem Class Reference

A robot subsystem. More...

#include <frc2/command/Subsystem.h>

Inheritance diagram for frc2::Subsystem:

Public Member Functions
virtual	~Subsystem ()
virtual void	Periodic ()
	This method is called periodically by the CommandScheduler. More...
virtual void	SimulationPeriodic ()
	This method is called periodically by the CommandScheduler. More...
template<class T , typename = std::enable_if_t<std::is_base_of_v< Command, std::remove_reference_t<T>>>>
void	SetDefaultCommand (T &&defaultCommand)
	Sets the default Command of the subsystem. More...
void	SetDefaultCommand (CommandPtr &&defaultCommand)
	Sets the default Command of the subsystem. More...
void	RemoveDefaultCommand ()
	Removes the default command for the subsystem. More...
Command *	GetDefaultCommand () const
	Gets the default command for this subsystem. More...
Command *	GetCurrentCommand () const
	Returns the command currently running on this subsystem. More...
void	Register ()
	Registers this subsystem with the CommandScheduler, allowing its Periodic() method to be called when the scheduler runs. More...
CommandPtr	RunOnce (std::function< void()> action)
	Constructs a command that runs an action once and finishes. More...
CommandPtr	Run (std::function< void()> action)
	Constructs a command that runs an action every iteration until interrupted. More...
CommandPtr	StartEnd (std::function< void()> start, std::function< void()> end)
	Constructs a command that runs an action once and another action when the command is interrupted. More...
CommandPtr	RunEnd (std::function< void()> run, std::function< void()> end)
	Constructs a command that runs an action every iteration until interrupted, and then runs a second action. More...

Detailed Description

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.

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.

This class is provided by the NewCommands VendorDep

See also

Command

CommandScheduler

SubsystemBase

Constructor & Destructor Documentation

~Subsystem()

virtual frc2::Subsystem::~Subsystem ( )

virtual

Member Function Documentation

GetCurrentCommand()

Command * frc2::Subsystem::GetCurrentCommand

(

)

const

Returns the command currently running on this subsystem.

Returns null if no command is currently scheduled that requires this subsystem.

Returns

the scheduled command currently requiring this subsystem

GetDefaultCommand()

Command * frc2::Subsystem::GetDefaultCommand

(

)

const

Gets the default command for this subsystem.

Returns null if no default command is currently associated with the subsystem.

Returns

the default command associated with this subsystem

Periodic()

virtual void frc2::Subsystem::Periodic ( )

virtual

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.

Reimplemented in frc2::PIDSubsystem, frc2::ProfiledPIDSubsystem< Distance >, and frc2::TrapezoidProfileSubsystem< Distance >.

Register()

void frc2::Subsystem::Register

(

)

Registers this subsystem with the CommandScheduler, allowing its Periodic() method to be called when the scheduler runs.

RemoveDefaultCommand()

void frc2::Subsystem::RemoveDefaultCommand

(

)

Removes the default command for the subsystem.

This will not cancel the default command if it is currently running.

Run()

CommandPtr frc2::Subsystem::Run

(

std::function< void()>

action

)

Constructs a command that runs an action every iteration until interrupted.

Requires this subsystem.

Parameters

action

the action to run

RunEnd()

CommandPtr frc2::Subsystem::RunEnd	(	std::function< void()>	run,
		std::function< void()>	end
	)

Constructs a command that runs an action every iteration until interrupted, and then runs a second action.

Requires this subsystem.

Parameters

run	the action to run every iteration
end	the action to run on interrupt

RunOnce()

CommandPtr frc2::Subsystem::RunOnce

(

std::function< void()>

action

)

Constructs a command that runs an action once and finishes.

Requires this subsystem.

Parameters

action

the action to run

SetDefaultCommand() [1/2]

void frc2::Subsystem::SetDefaultCommand

(

CommandPtr &&

defaultCommand

)

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.

Parameters

defaultCommand

the default command to associate with this subsystem

SetDefaultCommand() [2/2]

template<class T , typename = std::enable_if_t<std::is_base_of_v< Command, std::remove_reference_t<T>>>>

void frc2::Subsystem::SetDefaultCommand ( T &&  defaultCommand )

inline

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.

Parameters

defaultCommand

the default command to associate with this subsystem

SimulationPeriodic()

virtual void frc2::Subsystem::SimulationPeriodic ( )

virtual

This method is called periodically by the CommandScheduler.

Useful for updating subsystem-specific state that needs to be maintained for simulations, such as for updating simulation classes and setting simulated sensor readings.

StartEnd()

CommandPtr frc2::Subsystem::StartEnd	(	std::function< void()>	start,
		std::function< void()>	end
	)

Constructs a command that runs an action once and another action when the command is interrupted.

Requires this subsystem.

Parameters

start	the action to run on start
end	the action to run on interrupt

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The documentation for this class was generated from the following file:

• frc2/command/Subsystem.h