gen_event能查看的例子不多，把网上的做个标记
curling_scoreboard_hw.erl
-module(curling_scoreboard_hw).
-export([add_point/1, next_round/0, set_teams/2, reset_board/0]).
%% This is a 'dumb' module that's only there to replace what a real hardware
%% controller would likely do. The real hardware controller would likely hold
%% some state and make sure everything works right, but this one doesn't mind.
%% Shows the teams on the scoreboard.
set_teams(TeamA, TeamB) ->
io:format("Scoreboard: Team ~s vs. Team ~s~n", [TeamA, TeamB]).
next_round() ->
io:format("Scoreboard: round over~n").
add_point(Team) ->
io:format("Scoreboard: increased score of team ~s by 1~n", [Team]).
reset_board() ->
io:format("Scoreboard: All teams are undefined and all scores are 0~n").
curling_scoreboard.erl
-module(curling_scoreboard).
-behaviour(gen_event).
-export([init/1, handle_event/2, handle_call/2, handle_info/2, code_change/3,
terminate/2]).
init([]) ->
{ok, []}.
handle_event({set_teams, TeamA, TeamB}, State) ->
curling_scoreboard_hw:set_teams(TeamA, TeamB),
{ok, State};
handle_event({add_points, Team, N}, State) ->
[curling_scoreboard_hw:add_point(Team) || _ <- lists:seq(1,N)],
{ok, State};
handle_event(next_round, State) ->
curling_scoreboard_hw:next_round(),
{ok, State};
handle_event(_, State) ->
{ok, State}.
handle_call(_, State) ->
{ok, ok, State}.
handle_info(_, State) ->
{ok, State}.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
terminate(_Reason, _State) ->
ok.
使用方法
1> c(curling_scoreboard_hw).
{ok,curling_scoreboard_hw}
2> c(curling_scoreboard).
{ok,curling_scoreboard}
3> {ok, Pid} = gen_event:start_link().
{ok,<0.43.0>}
4> gen_event:add_handler(Pid, curling_scoreboard, []).
ok
5> gen_event:notify(Pid, {set_teams, "Pirates", "Scotsmen"}).
Scoreboard: Team Pirates vs. Team Scotsmen
ok
6> gen_event:notify(Pid, {add_points, "Pirates", 3}).
ok
Scoreboard: increased score of team Pirates by 1
Scoreboard: increased score of team Pirates by 1
Scoreboard: increased score of team Pirates by 1
7> gen_event:notify(Pid, next_round).
Scoreboard: round over
ok
8> gen_event:delete_handler(Pid, curling_scoreboard, turn_off).
ok
9> gen_event:notify(Pid, next_round).
ok