我正在尝试为我的Android聊天应用程序使用Erlang模块，但我不确定正确的语法，因为这个模块是在几年前创建的，而且在Erlang上有所改变。我不太了解Erlang，所以我做了第一次改编，但Case表达式有些奇怪，似乎字符串没有正确匹配。
原始模块是mod_confirm_delivery，如下所示
%% name of module must match file name
-module(mod_confirm_delivery).
-author("Johan Vorster").
%% Every ejabberd module implements the gen_mod behavior
%% The gen_mod behavior requires two functions: start/2 and stop/1
-behaviour(gen_mod).
%% public methods for this module
-export([start/2, stop/1, send_packet/3, receive_packet/4, get_session/5, set_offline_message/5]).
%% included for writing to ejabberd log file
-include("ejabberd.hrl").
-include("logger.hrl").
-record(session, {sid, usr, us, priority, info}).
-record(offline_msg, {us, timestamp, expire, from, to, packet}).
-record(confirm_delivery, {messageid, timerref}).
start(_Host, _Opt) ->
?INFO_MSG("mod_confirm_delivery loading", []),
mnesia:create_table(confirm_delivery,
[{attributes, record_info(fields, confirm_delivery)}]),
mnesia:clear_table(confirm_delivery),
?INFO_MSG("created timer ref table", []),
?INFO_MSG("start user_send_packet hook", []),
ejabberd_hooks:add(user_send_packet, _Host, ?MODULE, send_packet, 50),
?INFO_MSG("start user_receive_packet hook", []),
ejabberd_hooks:add(user_receive_packet, _Host, ?MODULE, receive_packet, 50).
stop(_Host) ->
?INFO_MSG("stopping mod_confirm_delivery", []),
ejabberd_hooks:delete(user_send_packet, _Host, ?MODULE, send_packet, 50),
ejabberd_hooks:delete(user_receive_packet, _Host, ?MODULE, receive_packet, 50).
send_packet(From, To, Packet) ->
?INFO_MSG("send_packet FromJID ~p ToJID ~p Packet ~p~n",[From, To, Packet]),
Type = xml:get_tag_attr_s("type", Packet),
?INFO_MSG("Message Type ~p~n",[Type]),
Body = xml:get_path_s(Packet, [{elem, "body"}, cdata]),
?INFO_MSG("Message Body ~p~n",[Body]),
MessageId = xml:get_tag_attr_s("id", Packet),
?INFO_MSG("send_packet MessageId ~p~n",[MessageId]),
LUser = element(2, To),
?INFO_MSG("send_packet LUser ~p~n",[LUser]),
LServer = element(3, To),
?INFO_MSG("send_packet LServer ~p~n",[LServer]),
Sessions = mnesia:dirty_index_read(session, {LUser, LServer}, #session.us),
?INFO_MSG("Session: ~p~n",[Sessions]),
case Type =:= "chat" andalso Body =/= [] andalso Sessions =/= [] of
true ->
{ok, Ref} = timer:apply_after(10000, mod_confirm_delivery, get_session, [LUser, LServer, From, To, Packet]),
?INFO_MSG("Saving To ~p Ref ~p~n",[MessageId, Ref]),
F = fun() ->
mnesia:write(#confirm_delivery{messageid=MessageId, timerref=Ref})
end,
mnesia:transaction(F);
_ ->
ok
end.
receive_packet(_JID, From, To, Packet) ->
?INFO_MSG("receive_packet JID: ~p From: ~p To: ~p Packet: ~p~n",[_JID, From, To, Packet]),
Received = xml:get_subtag(Packet, "received"),
?INFO_MSG("receive_packet Received Tag ~p~n",[Received]),
if Received =/= false andalso Received =/= [] ->
MessageId = xml:get_tag_attr_s("id", Received),
?INFO_MSG("receive_packet MessageId ~p~n",[MessageId]);
true ->
MessageId = []
end,
if MessageId =/= [] ->
Record = mnesia:dirty_read(confirm_delivery, MessageId),
?INFO_MSG("receive_packet Record: ~p~n",[Record]);
true ->
Record = []
end,
if Record =/= [] ->
[R] = Record,
?INFO_MSG("receive_packet Record Elements ~p~n",[R]),
Ref = element(3, R),
?INFO_MSG("receive_packet Cancel Timer ~p~n",[Ref]),
timer:cancel(Ref),
mnesia:dirty_delete(confirm_delivery, MessageId),
?INFO_MSG("confirm_delivery clean up",[]);
true ->
ok
end.
get_session(User, Server, From, To, Packet) ->
?INFO_MSG("get_session User: ~p Server: ~p From: ~p To ~p Packet ~p~n",[User, Server, From, To, Packet]),
ejabberd_router:route(From, To, Packet),
?INFO_MSG("Resend message",[]),
set_offline_message(User, Server, From, To, Packet),
?INFO_MSG("Set offline message",[]),
MessageId = xml:get_tag_attr_s("id", Packet),
?INFO_MSG("get_session MessageId ~p~n",[MessageId]),
case MessageId =/= [] of
true ->
mnesia:dirty_delete(confirm_delivery, MessageId),
?INFO_MSG("confirm_delivery clean up",[]);
_ ->
ok
end.
set_offline_message(User, Server, From, To, Packet) ->
?INFO_MSG("set_offline_message User: ~p Server: ~p From: ~p To ~p Packet ~p~n",[User, Server, From, To, Packet]),
F = fun() ->
mnesia:write(#offline_msg{us = {User, Server}, timestamp = now(), expire = "never", from = From, to = To, packet = Packet})
end,
mnesia:transaction(F).
这里有我的更改模块，Case是send_packet方法中的一个。
Type = xml:get_tag_attr_s("type", Packet),
上面一行返回＆lt;＆lt;“chat”＆gt;＆gt;作为类型，但我认为不匹配案例类型=：=“聊天”，其他tag_attr也包含在＆lt;＆lt;“”＆gt;＆gt;内
%% name of module must match file name
-module(mod_confirm_delivery).
-author("Johan Vorster").
%% Every ejabberd module implements the gen_mod behavior
%% The gen_mod behavior requires two functions: start/2 and stop/1
-behaviour(gen_mod).
%% public methods for this module
-export([start/2, stop/1, send_packet/4, receive_packet/5, get_session/5, set_offline_message/5]).
%% included for writing to ejabberd log file
-include("ejabberd.hrl").
-include("logger.hrl").
-record(session, {sid, usr, us, priority, info}).
-record(offline_msg, {us, timestamp, expire, from, to, packet}).
-record(confirm_delivery, {messageid, timerref}).
start(_Host, _Opt) ->
?DEBUG("mod_confirm_delivery loading", []),
mnesia:create_table(confirm_delivery,
[{attributes, record_info(fields, confirm_delivery)}]),
mnesia:clear_table(confirm_delivery),
?DEBUG("created timer ref table", []),
?DEBUG("start user_send_packet hook", []),
ejabberd_hooks:add(user_send_packet, _Host, ?MODULE, send_packet, 50),
?DEBUG("start user_receive_packet hook", []),
ejabberd_hooks:add(user_receive_packet, _Host, ?MODULE, receive_packet, 50).
stop(_Host) ->
?DEBUG("stopping mod_confirm_delivery", []),
ejabberd_hooks:delete(user_send_packet, _Host, ?MODULE, send_packet, 50),
ejabberd_hooks:delete(user_receive_packet, _Host, ?MODULE, receive_packet, 50).
%%send_packet(From, To, Packet) ->
send_packet(Packet, C2SState, From, To) ->
%% ?INFO_MSG("send_packet FromJID ~p ToJID ~p Packet ~p~n",[From, To, Packet]),
?DEBUG("send_packet Packet ~p C2SState ~p FromJID ~p ToJID ~p~n",[Packet, C2SState, From, To]),
Type = fxml:get_tag_attr_s(<<"type">>, Packet),
?DEBUG("Message Type ~p~n",[Type]),
Body = fxml:get_path_s(Packet, [{elem, <<"body">>}, cdata]),
?DEBUG("Message Body ~p~n",[Body]),
MessageId = fxml:get_tag_attr_s(<<"id">>, Packet),
?DEBUG("send_packet MessageId ~p~n",[MessageId]),
LUser = element(2, To),
?DEBUG("send_packet LUser ~p~n",[LUser]),
LServer = element(3, To),
?DEBUG("send_packet LServer ~p~n",[LServer]),
Sessions = mnesia:dirty_index_read(session, {LUser, LServer}, #session.us),
?DEBUG("Session: ~p~n",[Sessions]),
case Type =:= "chat" andalso Body =/= [] andalso Sessions =/= [] of
true ->
{ok, Ref} = timer:apply_after(10000, mod_confirm_delivery, get_session, [LUser, LServer, From, To, Packet]),
?DEBUG("Saving To ~p Ref ~p~n",[MessageId, Ref]),
F = fun() ->
mnesia:write(#confirm_delivery{messageid=MessageId, timerref=Ref})
end,
mnesia:transaction(F);
_ ->
Packet
end.
receive_packet(Packet, C2SState, _JID, From, To) ->
?DEBUG("receive_packet JID: ~p From: ~p To: ~p Packet: ~p~n",[_JID, From, To, Packet]),
Received = fxml:get_subtag(Packet, <<"received">>),
?DEBUG("receive_packet Received Tag ~p~n",[Received]),
if Received =/= false andalso Received =/= [] ->
MessageId = fxml:get_tag_attr_s(<<"id">>, Received),
?DEBUG("receive_packet MessageId ~p~n",[MessageId]);
true ->
MessageId = []
end,
if MessageId =/= [] ->
Record = mnesia:dirty_read(confirm_delivery, MessageId),
?DEBUG("receive_packet Record: ~p~n",[Record]);
true ->
Record = []
end,
if Record =/= [] ->
[R] = Record,
?DEBUG("receive_packet Record Elements ~p~n",[R]),
Ref = element(3, R),
?DEBUG("receive_packet Cancel Timer ~p~n",[Ref]),
timer:cancel(Ref),
mnesia:dirty_delete(confirm_delivery, MessageId),
?DEBUG("confirm_delivery clean up",[]);
true ->
Packet
end.
get_session(User, Server, From, To, Packet) ->
?DEBUG("get_session User: ~p Server: ~p From: ~p To ~p Packet ~p~n",[User, Server, From, To, Packet]),
ejabberd_router:route(From, To, Packet),
?DEBUG("Resend message",[]),
set_offline_message(User, Server, From, To, Packet),
?DEBUG("Set offline message",[]),
MessageId = fxml:get_tag_attr_s(<<"id">>, Packet),
?DEBUG("get_session MessageId ~p~n",[MessageId]),
case MessageId =/= [] of
true ->
mnesia:dirty_delete(confirm_delivery, MessageId),
?DEBUG("confirm_delivery clean up",[]);
_ ->
ok
end.
set_offline_message(User, Server, From, To, Packet) ->
?DEBUG("set_offline_message User: ~p Server: ~p From: ~p To ~p Packet ~p~n",[User, Server, From, To, Packet]),
F = fun() ->
mnesia:write(#offline_msg{us = {User, Server}, timestamp = now(), expire = "never", from = From, to = To, packet = Packet})
end,
mnesia:transaction(F).
模块编译正常，也是开始。