Études for Erlang

Solution 11-3

Here is a suggested solution for Étude 11-3. Since the bulk of the code is identical to the previous étude, the only code shown here is the added and revised code.

%% @doc Connect to a named server
connect(ServerName) ->
  Result = net_adm:ping(ServerName),
  case Result of
    pong -> io:format("Connected to server.~n");
    pang -> io:format("Cannot connect to ~p.~n", [ServerName])
  end.

%% Wrapper to hide internal details when getting a weather report
report(Station) ->
  gen_server:call({global, weather}, Station).

%% Wrapper to hide internal details when getting a list of recently used
%% stations.
recent() ->
  gen_server:call({global,weather}, recent).

%%% convenience method for startup
start_link() ->
  gen_server:start_link({global, ?SERVER}, ?MODULE, [], []).

%%% gen_server callbacks
init([]) ->
  inets:start(),
  {ok, []}.

handle_call(recent, _From, State) ->
  {reply, State, State};
handle_call(Request, _From, State) ->
  {Reply, NewState} = get_weather(Request, State),
  {reply, Reply, NewState}.

handle_cast(_Message, State) ->
  io:format("Most recent requests: ~p\n", [State]),
  {noreply, State}.