gen_event

详细解释：参考文档http://erlangdisplay.iteye.com/blog/315391 上面代码好多错误


-module(recent_logger).
-behaviour(gen_event).

-export([start/0, stop/0, log/1, report/0, release/0]).

%% gen_event callbacks
-export([init/1, handle_event/2, handle_call/2, terminate/2,add_handler/0]).
-define(NAME, logger_manager).

add_handler()->
    gen_event:add_handler(?NAME, ?MODULE, [testinit]).

%% start behaviour
start() ->
    case gen_event:start_link({local, ?NAME}) of
        Ret = {ok, _Pid} ->
%            gen_event:add_handler(?NAME, ?MODULE, [testinit]),
            Ret;
        Other ->
            Other
    end.

%% stop
stop() ->
    gen_envent:stop(?NAME).

%% notify an envent about log
log(E) ->
    gen_event:notify(?NAME, {log, E}).

%% report the all log
report() ->
  gen_event:call(?NAME, ?MODULE, report).

%% release this handler
release() ->
  gen_event:delete_handler(?NAME, ?MODULE, release).

init(_Arg) ->
    io:format("start recent log handler  Arg=~p~n",[_Arg]),
    {ok, []}.

handle_event({log, E}, List) ->
    io:format("long E=~p, List=~p~n",[E,List]),
    {ok, trim([E | List])}.

handle_call(report, List) ->
    {ok,List,List} .

terminate(stop, _List) ->
    io:format("recent log handler stop~n"),
    ok;
terminate(release, _List) ->
    io:format("recent log handler release~n"),
    ok.

%% save the recent five log
trim([E1, E2, E3, E4, E5 | []]) ->
    [E1, E2, E3, E4, E5];
trim(List) ->
    List.