Interface Command

core/src/main/java/com/arcrobotics/ftclib/command/Command.java:23–304

A state machine representing a complete action to be performed by the robot. Commands are run by the CommandScheduler, and can be composed into CommandGroups to allow users to build complicated multi-step actions without the need to roll the state machine logic themselves. Commands are

 * @author Jackson
 */
@SuppressWarnings("PMD.TooManyMethods")
public interface Command {

    /**
     * The initial subroutine of a command.  Called once when the command is initially scheduled.
     */
    default void initialize() {
    }

    /**
     * The main body of a command.  Called repeatedly while the command is scheduled.
     */
    default void execute() {
    }

    /**
     * The action to take when the command ends.  Called when either the command finishes normally,
     * or when it interrupted/canceled.
     *
     * @param interrupted whether the command was interrupted/canceled
     */
    default void end(boolean interrupted) {
    }

    /**
     * Whether the command has finished.  Once a command finishes, the scheduler will call its
     * end() method and un-schedule it.
     *
     * @return whether the command has finished.
     */
    default boolean isFinished() {
        return false;
    }

    /**
     * Specifies the set of subsystems used by this command.  Two commands cannot use the same
     * subsystem at the same time.  If the command is scheduled as interruptible and another
     * command is scheduled that shares a requirement, the command will be interrupted.  Else,
     * the command will not be scheduled.  If no subsystems are required, return an empty set.
     *
     * <p>Note: it is recommended that user implementations contain the requirements as a field,
     * and return that field here, rather than allocating a new set every time this is called.
     *
     * @return the set of subsystems that are required
     */
    Set<Subsystem> getRequirements();

    /**
     * Decorates this command with a timeout.  If the specified timeout is exceeded before the command
     * finishes normally, the command will be interrupted and un-scheduled.  Note that the
     * timeout only applies to the command returned by this method; the calling command is
     * not itself changed.
     *
     * <p>Note: This decorator works by composing this command within a CommandGroup.  The command
     * cannot be used independently after being decorated, or be re-decorated with a different
     * decorator, unless it is manually cleared from the list of grouped commands with
     * {@link CommandGroupBase#clearGroupedCommand(Command)}.  The decorated command can, however, be
     * further decorated without issue.