Do something after method returns

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.

Looks like delegation. plan() is, here, setting up the delegation and executePlanned() is invoking the queued actions. — sorpigal, Nov 29 '10 at 17:06

score 1 · Accepted Answer · answered Nov 29 '10 at 17:06

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.

score 0 · Answer 2 · answered Nov 29 '10 at 17:04

0

Can you not send the response first and then do the "if(playersConnected" check after?

answered Nov 29 '10 at 17:04

jzd

23,473
9
54
76

In my current setup, the response has to be returned by the function that checks whether all players are connected – Bart van Heukelom Nov 29 '10 at 23:14

score 0 · Answer 3 · answered Nov 29 '10 at 17:04

0

I'm not sure about this closure syntax you have here. Can you just have this instead?

function onRequest() {
    playersConnected++;

    sendResponse(OK);

    if (playersConnected == 4) {
        sendAllPlayersTheirCards()
    }
}

answered Nov 29 '10 at 17:04

daveb

74,111
6
45
51

I can't because the code that handles the receiving of the request and the sending of the response is part of a generic package, and the code that does playersConnected++ is part of another, game-specific package. – Bart van Heukelom Nov 29 '10 at 23:08

score 0 · Answer 4 · edited Aug 03 '12 at 00:15

0

This seems like a relevant tutorial:

Using Callable to Return Results From Runnables

edited Aug 03 '12 at 00:15

Bill the Lizard

398,270
210
566
880

answered Nov 29 '10 at 17:07

Sean Patrick Floyd

292,901
67
465
588

score 0 · Answer 5 · answered Nov 29 '10 at 23:12

I could do it like this:

function onRequest(request) {

 game.handleRequest(request, function(response) {
  sendResponse(response);
 }

}

class game
function handleRequest(request, sendResponse:Function) {
 players++;
 sendResponse(OK);
 if (players == 4) sendCards();
}

Do something after method returns

5 Answers5