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Message Queues for Elm

Elmq provides a way to send and receive messages over named channels.

A message can be sent, resulting in a Cmd to Elm. A message can be received by forming a subscription on a channel.

Thanks to Gusztáv Szikszai, who is the original author of this code. This was lifted from his elm-ui project, which can be found here:


This example shows how to set up a channel named "chat.elm" and to send and receive string messages over that channel:

import Elmq

-- To send string messages to the "chat.elm" channel.
elmTalk : String -> Cmd msg
elmTalk message =
    Elmq.sendString "chat.elm" message

-- To receive string message on the "chat.elm" channel
type Msg =
    ReceiveChat String

subscriptions : Model -> Sub Msg
subscriptions model =
    Elmq.listenString "chat.elm" ReceiveChat

Future direction:

A general purpose asynchronous messaging feature might be a welcome addition to Elm. Here are some suggestions on future directions this work could take:

If two listeners are on the same channel to they both get all the messages (pub/sub style), or does each listener get each message uniquely (point-to-point style). Would likely want to support both models.

Should there be some significance to the channel names when subscribing? For example if channels are named with dot notation like newsgroups "comp.lang.elm", then can you create subscriptions spanning multiple channels like "comp.lang.*"?

When the type of data sent to a channel does not match the expected type being listened for, a default value is passed instead. Could there be a better way, which would be to not trigger a listener event at all when this happens?

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