Question

This is my situation in pseudocode:

function onRequest() {
    receiveConnectionRequest();

    response = function onConnect() {
        playersConnected++;
        if (playersConnected == 4) {
            sendAllPlayersTheirCards()
        }
        return OK;
    }();

    sendResponse(response);

}

When players 1-3 connect, they get added to the list of players and OK is returned to them, at which point they will set stuff up on their side. When player 4 connects, however, before the response to his request is sent, all players are sent their cards. Because player 4 has not received a response to his request yet, he hasn’t initialised correctly yet and errors upon receiving his cards.

What I’d like to have is this:

function onRequest() {
    receiveConnectionRequest();

    response = function onConnect() {
        playersConnected++;
        if (playersConnected == 4) {
            plan(sendAllPlayersTheirCards())
        }
        return OK;
    }();

    sendResponse(response);

    executePlanned() // now cards are sent
}

Is there a general pattern for that? The onConnect function is in a different class and should not be aware of the implementation details of onRequest.

I’m specifically trying to implement this in Java, but generic solutions are welcome.

Answer 1

Many good solutions to this, but I would suggest using a call back.

Don’t think of it as doing something after the method returns, think of it as calling back to report a state or trigger an event.

Search for event pattern , or call backs in Java. Here is one link I found.

The delegation pattern is very similar to.