flapjax get last element from eventstream

Question

flapjax get last element from eventstream

I am trying to implement a small chatservice using flapjax. I use an eventStream to get all the clients that connect to the server, and when broadcasting a message (the function on 'message') I map over this eventStream with the function that emits the message to the current client.

// Event stream yielding received clients
var clientReceiverE = receiverE();
// Event stream collecting all the clients
var clientsE = clientReceiverE.collectE([], function (client, clients) {return clients.concat([client]);});

socket.on('connection', function(client) {
    clientReceiverE.sendEvent(client);
    for (i = 0; i < chatMessages.length; i++) {
      client.emit('message', chatMessages[i]);
    }

    client.on('message', function(message) {
        chatMessages.push(message);
        //for (i = 0; i < clients.length; i++) {
        // clients[i].emit('message', message);
        //}
        mapE(clientReceiverE, function(client) {console.log(client); client.emit('message', message); return client});
    });

    client.on('nickname', function(name) {

    });
});

The registring of the clients on the eventstream succeeds with this code, but the mapE doesn't result in a loop over all this clients. Does anybody know what is wrong here?

node.js
socket.io

Answer 1

If you are still not guessed :) I think it's because mapE doesn't produce any action itself, mapE only creates and returns another EventStream which behaves like a given source, but with modified value by means of a given function.

Answer 2

You should not be using mapE like that. In your code you are attempting to recreate the mapE event bindings with each client.on('message', ...).

This problem is solved using a receiverE. This function is used to translate, external event streams into flapjax EventStream 's.

// Event stream yielding received clients
var clientReceiverE = receiverE();
// Event stream collecting all the clients
var clientsE = clientReceiverE.collectE([], function (client, clients) {return clients.concat([client]);});
var clientsB = clientsE.startsWith(undefined);    //Turn the event stream into a behaviour (event + value)

var messagesE = receiverE();
messagesE.mapE(function(messagePacket){
    var clients = clientsB.valueNow();     //Grab current value of client list behaviour
    if(clients==undefined){
       return;
    }
    var from = messagePacket.client;
    for(var index in clients){
       clients[index].emit('message', messagePacket.message);
       console.log(messagePacket.message);
    }
});

socket.on('connection', function(client) {
    clientReceiverE.sendEvent(client);

    client.on('message', function(message) {
        messagesE.sendEvent({client: client, message: message});
    });
});

The difference is this. The flapjax tree is isolated from the WebSocket event code and there is no shared state between them.