elma::StateMachine Class Reference

A finite state machine class. More...

#include <state_machine.h>

Inheritance diagram for elma::StateMachine:

Collaboration diagram for elma::StateMachine:

Public Member Functions
	StateMachine (std::string name)
	Construct a new StateMachine with the given name.
	StateMachine ()
	Construct an unnamed StateMachine.
StateMachine &	set_initial (State &s)
StateMachine &	add_transition (std::string event_name, State &from, State &to)
StateMachine &	set_propagate (bool val)
State &	current ()
void	init ()
	Do not override init() for a state machine.
void	start ()
	Do not override init() for a state machine.
void	update ()
	Do not override init() for a state machine.
void	stop ()
	Do not override init() for a state machine.
Public Member Functions inherited from elma::Process
	Process ()
	Default constructor. Names process "no name".
	Process (std::string name)
	Constructor that takes a name for the process. More...
string	name ()
status_type	status ()
high_resolution_clock::duration	period ()
int	num_updates ()
time_point< high_resolution_clock >	start_time ()
high_resolution_clock::duration	last_update ()
high_resolution_clock::duration	previous_update ()
Channel &	channel (string name)
	Access a channel with the given name. More...
double	milli_time ()
	The time since the last update in millisconds, as a double. More...
double	delta ()
	The most recent amount of time between updates. More...
void	watch (string event_name, std::function< void(Event &)> handler)
void	emit (const Event &event)
void	http_get (std::string url, std::function< void(json &)> handler)

Additional Inherited Members
Public Types inherited from elma::Process
enum	status_type { UNINITIALIZED, STOPPED, RUNNING }

Detailed Description

A finite state machine class.

Together with the State and Transition classes, this class is used to make a finite state machine process. For example, here is a toggle switch machine

#include <iostream>
#include <chrono>
#include "elma.h"


using namespace std::chrono;
using namespace elma;

class Trigger : public Process {
    public:
    Trigger() : Process("trigger") {}
    void init() {}
    void start() {}
    void update() { 
        std::cout << "switch at " << milli_time() << "\n";
        emit(Event("switch"));
    }
    void stop() {}
};

class Mode : public State {
    public:
    Mode(std::string name) : State(name) {}
    void entry(const Event& e) {
        std::cout << "entering " + name() << "\n";
    }
    void during() {}
    void exit(const Event&) {}
};

int main() {

    Manager m;
    Trigger trigger;
    Mode off("off"), on("on");
    StateMachine fsm("toggle switch");

    fsm.set_initial(off)
       .set_propagate(false)
       .add_transition("switch", off, on)
       .add_transition("switch", on, off);

    m.schedule(trigger, 1_ms)
     .schedule(fsm, 5_ms) // Doesn't matter since mode has empty update()
     .init()
     .run(11_ms);
     
}

Definition at line 13 of file state_machine.h.

Member Function Documentation

StateMachine & elma::StateMachine::add_transition	(	std::string	event_name,
		State &	from,
		State &	to
	)

Add a transition to the state machine

Parameters

event_name	Events with this name will trigger the transition
from	The state the machine must be in to take the transition
to	The state the machine will go to upon taking the transition

Returns

A reference to the state machine, for chaining

Definition at line 13 of file state_machine.cc.

State& elma::StateMachine::current ( )

inline

Returns

The current state

Definition at line 41 of file state_machine.h.

StateMachine & elma::StateMachine::set_initial

(

State &

s

)

Set the initial state of the state machine

Parameters

s	An instantiation of a class derived from State

Returns

A reference to the state machine, for chaining

Definition at line 8 of file state_machine.cc.

StateMachine& elma::StateMachine::set_propagate ( bool  val )

inline

Set whether the state machine should propagate transitions (default = false)

Parameters

val	True or false

Returns

A reference to the state machine, for chaining

Definition at line 38 of file state_machine.h.

---

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

• state_machine.h
• state_machine.cc