CODEWITHSUNDEEP
scalaplayframework
ryskajakub
ryskajakub

Reputation: 6431

Send a message from play's WebSocket immediately

I'm attempting to send a message to websocket instantly after the connection is estabilished. But I don't know, where to put the code with the message send.

def ws = WebSocket.async[String] {
    val (out, channel) = {
        Concurrent.broadcast[String]
    }
    channel push "message"
    request =>
        (in, out)
}

I can see, that when I send the message to the channel before the ws method returns, the web client doesn't get the message. If I manage to run the code channel push "message" after the method ws returns, it works fine and I receive the message at the browser client. I can delay it by wrapping the channel push "message" in Future{}, starting with some Thread.sleep().

But I hope, there some reliable, non-blocking solution...

Upvotes: 1

Views: 249

Answers (1)

pagoda_5b
pagoda_5b

Reputation: 7373

I see from the docs that async expects a lambda returning a Promise[stuff].

Supposing that (in, out) gets implicitly converted to said Promise you could try to explicitly create the promise and register a listener like

def ws = WebSocket.async[String] {
    val (out, channel) = {
        Concurrent.broadcast[String]
    }
    request =>
      val p = Promise((in, out))
      p.onRedeem(_ => channel push "message")
      p
}

I'm no Play! expert here, so I'm just guessing.

Upvotes: 2

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