[erlang-questions] gen_server and odbc problem about How to share a odbc connection

[Andreas Hillqvist]

Hi.

The scope of an variable is within the function. So you will have to
pass a long the ODBC connection. This is made avalible by the gen
servers state variable.

It is recomended to use an record for the state. But if you only have
one or a very limited amount ov state varaible, you could use a tuple
or a list:

init([]) ->
   process_flag(trap_exit, true),
   {ok,Conn} = odbc:connect("DSN=flashpk;"
                            "UID=flashpk;"
                            "PWD=flashpk",
                            [{trace_driver, on}]),
   {ok, Conn}.

handle_info({?PLLOGIN,Uid,Pwd}, Conn) ->
   odbc:sql_query(Conn, "INSERT INTO customer (cno, password)"
                        "VALUES ('root', '123456')"),
   {noreply, Conn}.

OR:

-record(state, {connection}).

init([]) ->
   process_flag(trap_exit, true),
   {ok,Conn} = odbc:connect("DSN=flashpk;"
                            "UID=flashpk;"
                            "PWD=flashpk",
                            [{trace_driver, on}]),
   State = #state{connection = Conn},
   {ok, State}.

handle_info({?PLLOGIN,Uid,Pwd}, #state{connection = Conn} = State) ->
   odbc:sql_query(Conn,
                  "INSERT INTO customer (cno, password)"
                  "VALUES ('root', '123456')"),
   {noreply, State}.


Kind regards
Andreas Hillqvist

2008/3/28, wenew zhang <wenewboy@REDACTED>:
> Dear All,
>      Maybe another low-level question,but it's make me confused,
>
> init([]) ->
>    process_flag(trap_exit, true),
>    io:format("Authserver init with []~n"),
> %    {ok,Bin}=file:consult(?AUTHCONF),
> %    DDsn=element(2,lists:nth(1,Bin)),
> %    Duser=element(2,lists:nth(2,Bin)),
> %    Dpwd=element(2,lists:nth(3,Bin)),
>    %%Ddatabase=element(2,lists:nth(4,Bin)),
> %    DSNString="DSN="++DDsn++";UID="++Duser++";PWD="++Dpwd,
> %    {ok,Conn}=odbc:connect(DSNString,[{trace_driver,on}]),%% read the
> odbc settings
> {ok,Conn}=odbc:connect("DSN=flashpk;UID=flashpk;PWD=flashpk",[{trace_driver,on}]),
>    {ok,0}.
>
> handle_info({?PLLOGIN,Uid,Pwd},_State) ->
>    io:format("PLLogin id:~w Uid:~w   Pwd:~w~n",[?PLLOGIN,Uid,Pwd]),
>    odbc:sql_query(Conn,"insert into customer(cno,password) values
> ('root','123456')"),
>    {noreply, _State}.
>
> i want share the Conn ,but i get the unbound error,
> so How to share a odbc connection?
> or anybody have other solutions?
>
> Best Regards
>
> wenew zhang
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