1 files changed, 45 insertions, 0 deletions
diff --git a/server/server.erl b/server/server.erl
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+%% ---
+%%  Excerpted from "Programming Erlang",
+%%  published by The Pragmatic Bookshelf.
+%%  Copyrights apply to this code. It may not be used to create training material,
+%%  courses, books, articles, and the like. Contact us if you are in doubt.
+%%  We make no guarantees that this code is fit for any purpose.
+%%  Visit http://www.pragmaticprogrammer.com/titles/jaerlang for more book information.
+%%---
+-module(server).
+-export([start/2, rpc/2, swap_code/2]).
+
+start(Name, Mod) ->
+    register(Name, spawn(fun() -> loop(Name,Mod,Mod:init()) end)).
+
+swap_code(Name, Mod) -> rpc(Name, {swap_code, Mod}).
+
+rpc(Name, Request) ->
+    Name ! {self(), Request},
+    receive
+        {Name, crash} -> exit(rpc);
+        {Name, ok, Response} -> Response
+    end.
+
+loop(Name, Mod, OldState) ->
+    receive
+        {From, {swap_code, NewCallbackMod}} ->
+            From ! {Name, ok, ack},
+            loop(Name, NewCallbackMod, OldState);
+        {From, Request} ->
+            try Mod:handle(From, Request, OldState) of
+                {Response, NewState} ->
+                    From ! {Name, ok, Response},
+                    loop(Name, Mod, NewState)
+            catch
+                _: Why ->
+                    log_the_error(Name, Request, Why),
+                    From ! {Name, crash},
+                    loop(Name, Mod, OldState)
+            end
+    end.
+
+log_the_error(Name, Request, Why) ->
+    io:format("Server ~p request ~p ~n"
+              "caused exception ~p~n",
+              [Name, Request, Why]).