我正在尝试从0.18升级到0.19的Elm。我的项目取决于0.18的elm-lang/websocket
?我似乎无法在0.19中找到相应的包。我错过了什么?
websocket
包目前正在为Elm 0.19重新设计,请参阅this issue:
此软件包尚未针对0.19进行更新。我听过很多人说他们需要更多来自这个软件包的功能,所以我宁愿在更新中考虑到这一点,而不仅仅是做同样的事情。我推荐使用端口或0.18,如果你真的需要这个权利这一秒。
下面是一个交互式表单的最小工作示例,用于回显echo.websocket.org的输入,使用2个简单的输入/输出端口与elm 0.19模块外部的JavaScript WebSocket对象进行通信:
文件:echo.elm。编译:elm make echo.elm --output=echo.js
port module Main exposing (main)
import Browser
import Html exposing (Html)
import Html.Attributes as HA
import Html.Events as HE
import Json.Encode as JE
-- JavaScript usage: app.ports.websocketIn.send(response);
port websocketIn : (String -> msg) -> Sub msg
-- JavaScript usage: app.ports.websocketOut.subscribe(handler);
port websocketOut : String -> Cmd msg
main = Browser.element
{ init = init
, update = update
, view = view
, subscriptions = subscriptions
}
{- MODEL -}
type alias Model =
{ responses : List String
, input : String
}
init : () -> (Model, Cmd Msg)
init _ =
( { responses = []
, input = ""
}
, Cmd.none
)
{- UPDATE -}
type Msg = Change String
| Submit String
| WebsocketIn String
update : Msg -> Model -> (Model, Cmd Msg)
update msg model =
case msg of
Change input ->
( { model | input = input }
, Cmd.none
)
Submit value ->
( model
, websocketOut value
)
WebsocketIn value ->
( { model | responses = value :: model.responses }
, Cmd.none
)
{- SUBSCRIPTIONS -}
subscriptions : Model -> Sub Msg
subscriptions model =
websocketIn WebsocketIn
{- VIEW -}
li : String -> Html Msg
li string = Html.li [] [Html.text string]
view : Model -> Html Msg
view model = Html.div []
--[ Html.form [HE.onSubmit (WebsocketIn model.input)] -- Short circuit to test without ports
[ Html.form [HE.onSubmit (Submit model.input)]
[ Html.input [HA.placeholder "Enter some text.", HA.value model.input, HE.onInput Change] []
, model.responses |> List.map li |> Html.ol []
]
]
将已编译的echo.js嵌入到echo.html中:
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Echo</title>
<script src="echo.js"></script>
</head>
<body>
<div id="elm-node"></div>
<script>
var app = Elm.Main.init({node: document.getElementById("elm-node")});
var ws = new WebSocket("wss://echo.websocket.org");
ws.onmessage = function(message)
{
console.log(message);
app.ports.websocketIn.send(JSON.stringify({data:message.data,timeStamp:message.timeStamp}));
};
app.ports.websocketOut.subscribe(function(msg) { ws.send(msg); });
</script>
</body>
</html>
这适用于Linux上的Firefox 60.2.0esr,但尚未在其他平台上进行过测试。
同样,这只是一个最小的例子来演示如何使用带有WebSockets的端口来实现Elm 0.19。它不包括关闭WebSocket,错误处理等,但希望这个例子可以帮助您开始朝这个方向发展。预计很快就会再次由Elm直接支持WebSockets,所以这只是一个临时的解决方案。如果您不需要升级到0.19,那么请考虑使用0.18。