How to keep track of a process per browser window and access it at each event in Nitrogen?

In Nitrogen, the Erlang web framework, I have the following problem. I have a process that takes care of sending and receiving messages to another process that acts as a hub. This process acts as the comet process to receive the messages and update the page.

The problem is that when the user process a button I get a call to event. How do I get ahold of that Pid at an event.

the code that initiates the communication and sets up the receiving part looks like this, first I have an event which starts the client process by calling wf:comet:

event(start_chat) -> 
  Client = wf:comet(fun() -> chat_client() end);

The code for the client process is the following, which gets and joins a room at the beginning and then goes into a loop sending and receiving messages to/from the room:

chat_client() -> 
  Room = room_provider:get_room(), 
  room:join(Room), 
  chat_client(Room).

chat_client(Room) -> 
  receive
    {send_message, Message} ->
      room:send_message(Room, Message);
    {message, From, Message} -> 
      wf:insert_bottom(messages, [#p{}, #span { text=Message }]), 
      wf:comet_flush()
  end, 
  chat_client(Room).

Now, here's the problem. I have another event, send_message:

event(send_message) ->
  Message = wf:q(message),
  ClientPid ! {send_message, Message}.

except that ClientPid is not defined there, and I can't see how to get ahold of it. Any ideas?

The related threat at the Nitrogen mailing list: htt开发者_如何学Gop://groups.google.com/group/nitrogenweb/browse_thread/thread/c6d9927467e2a51a

Nitrogen provides a key-value storage per page instance called state. From the documentation:

Retrieve a page state value stored under the specified key. Page State is different from Session State in that Page State is scoped to a series of requests by one user to one Nitrogen Page:

wf:state(Key) -> Value

Store a page state variable for the current user. Page State is different from Session State in that Page State is scoped to a series of requests by one user to one Nitrogen Page:

wf:state(Key, Value) -> ok

Clear a user's page state:

wf:clear_state() -> ok

Have an ets table which maps session id's to client Pid's. Or if nitrogen provides any sort of session management, store the Pid as session data.

Every thing that needs to be remembered needs a process. It looks like your room provider isn't.

room:join(Room) need to be room:join(Room,self()). The room need to know what your comet-process pid is.

To send a message to a client you first send the message to the room, the room will then send a message to all clients in the room. But for that to work. Every client joining the room need to submit the comet-pid. The room need to keep a list of all pid's in the room.