Erlang: list all records - erlang

Question

Please help me, (btw my English is not very good). I want to list all records that have been created for a gen_server, for example, if a had the following code:
-module(mod).
-record(person, {name, phone}).
start_link(Param1, Param2) ->
gen_server:start_link(?MODULE, [Param1, Param2], []).
init([Param1, Param2]) ->
{ok, #person{name=Param1,phone=Param2}}.
I can called:
mod:start_link(Maria,22222).
mod:start_link(Jose,9348).
mod:start_link(lol,232).
After that i want to see all the records that i have created and put it on a list. How can i do this?

Answer 1

You should read this doc: http://www.erlang.org/doc/man/gen_server.html#start_link-3.
The start_link/3 just start the gen_server, do store the record data.
-module(record_make).
-compile(export_all).
-export([init/1, handle_call/3, handle_cast/2, handle_info/2, terminate/2, code_change/3]).
-behaviour(gen_server).
-define(SERVER, ?MODULE).
-record(state, {persons = []}).
-record(person, {name, phone}).
start_link() ->
gen_server:start_link({local, ?SERVER}, ?MODULE, [], []).
init([]) ->
{ok, #state{}}.
handle_call({create, Name, Phone}, _Frome, State = #state{persons = Persons}) ->
NewPerson = #person{name = Name, phone = Phone},
{reply, ok, State#state{persons = [NewPerson | Persons]}};
handle_call(list, _From, State = #state{persons = Persons}) ->
io:format("~p~n", [Persons]),
{reply, ok, State};
handle_call(_Request, _From, State) ->
Reply = ok,
{reply, Reply, State}.
handle_cast(_Msg, State) ->
{noreply, State}.
handle_info(_Info, State) ->
{noreply, State}.
terminate(_Reason, _State) ->
ok.
code_change(_OldVsn, State, _Extra) ->
{ok, State}.
create(Name, Phone) ->
gen_server:call(?MODULE, {create, Name, Phone}).
list() ->
gen_server:call(?MODULE, list).
You can do like this:
1> c(record_make)
1> .
{ok,record_make}
2> record_make:start_link().
{ok,<0.41.0>}
3> record_make:create("yang", "123").
ok
4> record_make:create("zhang", "456").
ok
5> record_make:list().
[{person,"zhang","456"},{person,"yang","123"}]
ok
6>

Answer 2

No chance to get the information in this way: there is one record per gen_server and the information is lost as soon as the sever die. If you need this information you shold add a dedicated process to keep the information ({Pid,Record} or record number ...). The information can be updated during the init and the terminate function via function such as record_manager:create/1 and record_manager:delete/1. You can also store them in a shared ets.