Difficulty adopting gen_server architecture in erlang - erlang

Question

I am relatively new to erlang and wrote following modules:
-module(gserver).
-export([start1/0]).
-define(SERVER, gserver).
start1() ->
serv_util:start(?SERVER,
{ gserver, game_loop,
[dict:new(), dict:new()]}).
serv_util:
-module(serv_util).
-export([start/2]).
start(ServerName, {Module, Function, Args}) ->
global:trans({ServerName, ServerName},
fun() ->
case global:whereis_name(ServerName) of
undefined ->
Pid = spawn(Module, Function, Args),
global:register_name(ServerName, Pid);
_ ->
ok
end
end).
Then I tried to bring it under gen_server architecture of erlang as below:
-module(s_child).
-behaviour(gen_server).
-export([start/0,stop/0]).
-export([init/1, handle_call/3,handle_cast/2, terminate/2,
handle_info/2,code_change/3]).
-import(gserver,[start1/0]).
-import(gclient,[login/1]).
start()->
gserver:start1(),
gen_server:start_link({global,?MODULE}, ?MODULE, [], []).
stop()->
gen_server:cast(?MODULE, {stop}).
log_in(Name)->
gen_server:call({global,?MODULE}, {login,Name,self()}).
init(_Args) ->
io:format("Hello started ~n"),
{ok,_Args}.
handle_call({login,Name},_From,State)->
State,
Reply=login(Name),
{reply, Reply,State}.
But when i call this in the following order
1)s_sup:start_link().
Hello,started
{ok,<0.344.0>}
2)s_child:log_in("Abhishek").
** exception exit: {{function_clause,
[{s_child,handle_call,
[{login,"Abhishek",<0.335.0>},
{<0.335.0>,#Ref<0.0.4.457>},
[]],
[{file,"s_child.erl"},{line,61}]},
{gen_server,try_handle_call,4,
[{file,"gen_server.erl"},{line,615}]},
{gen_server,handle_msg,5,
[{file,"gen_server.erl"},{line,647}]},
{proc_lib,init_p_do_apply,3,
[{file,"proc_lib.erl"},{line,247}]}]},
{gen_server,call,
[{global,s_child},{login,"Abhishek",<0.335.0>}]}}
in function gen_server:call/2 (gen_server.erl, line 204)
And I am not able to understand that what exactly is wrong at line 61 in my code.In the complete code at line 61 Following code is present:
handle_call(stop, _From, State) ->
{stop, normal, ok, State};
i.e the first handle_call is present at line 61
Can anybody help me out here please.

Answer 1

In the log_in function, you pass {login,Name,self()} as the gen_server call, but the handle_call function only expects {login,Name}. Thus, since there is no matching clause, the call to handle_call fails.
You don't need to pass self(), as you use the reply feature to ensure that the response makes it back to the caller, so just modify log_in to pass {login,Name} to gen_server:call.

Answer 2

Legoscia's answer is right.
I recommend to see Understanding gen_server.
This article gives useful information for working with gen_server.