gen_fsm sample(すごいErlangゆかいに学ぼう! 15章)

stupid_dog_fsm.erl

-module(stupid_dog_fsm).
-author('ryuone<ryuone@gmail.com>').

-behaviour(gen_fsm).

-export([start_link/0]).
-export([init/1, handle_event/3, handle_sync_event/4, handle_info/3, terminate/3, code_change/4]).
-export([sit/3, bark/3, wag_tail/3]).
-export([get_sync_state/1]).
-export([test/0]).

-record(state, {name}).

start_link() ->
  {ok, proc_lib:spawn_link(?MODULE, init, [self()])}.

init(_Args) ->
  process_flag(trap_exit, true),
  State = #state{name = ryuone},
  gen_fsm:enter_loop(?MODULE, [], sit, State).

handle_event(stop, _StateName, State) ->
  {stop, normal, State}.

handle_sync_event(get_state, _From, StateName, State) ->
  {reply, StateName, StateName, State};
handle_sync_event(stop, _From, _StateName, State) ->
  {stop, normal, error, State};
handle_sync_event(Event, _From, StateName, State) ->
  io:format("Event : ~p~n", [Event]),
  {reply, StateName, StateName, State}.

handle_info(_Info, StateName, State) ->
  {next_state, StateName, State}.

code_change(iOldVsn, StateName, State, _) ->
  {ok, StateName, State}.

terminate(Reason, _StateName, _State) ->
  io:format("terminate called with ~p~n", [Reason]),
  ok.

%%
%% State
%%
sit(Event=see_squirrel, From, State) ->
  io:format("Current state is sit. Event is ~p~n", [Event]),
  gen_fsm:reply(From, "  State will change to bark."),
  {next_state, bark, State}.

bark(Event=get_petted, From, State) ->
  io:format("Current state is bark. Event is ~p~n", [Event]),
  gen_fsm:reply(From, "  State will change to get_petted."),
  {next_state, wag_tail, State}.

wag_tail(Event=wait, From, State) ->
  io:format("Current state is wag_tail. Event is ~p~n", [Event]),
  gen_fsm:reply(From, "  State will change to bark."),
  {next_state, bark, State};
wag_tail(Event=get_petted, From, State) ->
  io:format("Current state is wag_tail. Event is ~p~n", [Event]),
  gen_fsm:reply(From, "  State will change to sit."),
  {next_state, sit, State}.

%%
%% stupid_dog_fsm functins.
%%
get_sync_state(Pid) ->
  gen_fsm:sync_send_all_state_event(Pid, get_state).

%%
%% Test function.
%%
test() ->
  {ok, Pid} = start_link(),
  Res = gen_fsm:sync_send_all_state_event(Pid, get_state),
  % * Current state : sit 
  io:format("* Current state : ~p~n", [Res]),
  Ret1 = gen_fsm:sync_send_event(Pid, see_squirrel),
  % Current state is sit. Event is see_squirrel
  %   State will change to bark.
  io:format("~s~n", [Ret1]),
  Ret2 = gen_fsm:sync_send_event(Pid, get_petted),
  % Current state is bark. Event is get_petted
  %   State will change to get_petted.
  io:format("~s~n", [Ret2]),
  Ret3 = gen_fsm:sync_send_event(Pid, get_petted),
  % Current state is wag_tail. Event is get_petted
  %   State will change to sit.
  io:format("~s~n", [Ret3]),
  ok = gen_fsm:stop(Pid),
  ok.