Copyright	(C) 2016-2026 David M. Johnson
License	BSD3-style (see the file LICENSE)
Maintainer	David M. Johnson <code@dmj.io>
Stability	experimental
Portability	non-portable
Safe Haskell	None
Language	Haskell2010

Miso.EventSource

Contents

EventSource
Defaults
Types
Re-exports

Description

Interface to the browser's Server-Sent Events API, which provides a persistent, unidirectional stream of text or JSON messages pushed from a server to the browser client.

Typical usage inside an update function:

update FetchStream =
  connectText "/events" StreamOpened GotMessage StreamError
update (GotMessage msg) =
  modify (\m -> m { messages = msg : messages m })

close shuts down an open EventSource connection. socketState reads the current ready-state, and emptyEventSource provides a zero-value for use in the model before a connection is established.

Synopsis

connectText :: URL -> (EventSource -> action) -> (MisoString -> action) -> (MisoString -> action) -> Effect parent props model action
connectJSON :: FromJSON value => URL -> (EventSource -> action) -> (value -> action) -> (MisoString -> action) -> Effect parent props model action
close :: EventSource -> Effect parent props model action
socketState :: WebSocket -> (SocketState -> action) -> Effect parent props model action
emptyEventSource :: EventSource
newtype EventSource = EventSource Int
type URL = MisoString
data Payload value
- = JSON value
- | BLOB Blob
- | TEXT MisoString
- | BUFFER ArrayBuffer

EventSource

connectText Source #

Arguments

:: URL	URL endpoint for the Server-Sent Events stream
-> (EventSource -> action)	`onOpen` callback; receives the live `EventSource` handle
-> (MisoString -> action)	`onMessage` callback; receives each raw text message
-> (MisoString -> action)	`onError` callback; receives an error description
-> Effect parent props model action

Open a Server-Sent Events connection that delivers raw MisoString messages.

The three callbacks map browser events to action values dispatched into the MVU loop:

onOpen — receives the live EventSource handle (store it in the model to close it later)
onMessage — called with each message payload as a plain string
onError — called with a description of the connection error

See https://developer.mozilla.org/en-US/docs/Web/API/EventSource

connectJSON Source #

Arguments

:: FromJSON value
=> URL	URL endpoint for the Server-Sent Events stream
-> (EventSource -> action)	`onOpen` callback; receives the live `EventSource` handle
-> (value -> action)	`onMessage` callback; receives each JSON-decoded message
-> (MisoString -> action)	`onError` callback; receives an error description
-> Effect parent props model action

Open a Server-Sent Events connection that decodes each message as JSON.

Identical to connectText but the onMessage callback receives a parsed Haskell value of type value (via FromJSON) rather than a raw string. JSON decode failures are silently dropped; use connectText and decode manually if you need error recovery.

See https://developer.mozilla.org/en-US/docs/Web/API/EventSource

close Source #

Arguments

:: EventSource	The `EventSource` handle to close
-> Effect parent props model action

Close an open EventSource connection.

After calling close, no further onMessage or onError callbacks will fire. Corresponds to EventSource.close().

socketState :: WebSocket -> (SocketState -> action) -> Effect parent props model action Source #

Retrieves current status of WebSocket

If the WebSocket identifier does not exist a CLOSED is returned.

Defaults

emptyEventSource :: EventSource Source #

A null EventSource is one with a negative descriptor.

Types

newtype EventSource Source #

A type for holding an EventSource descriptor.

Constructors

EventSource Int

Instances

Instances details

Num EventSource Source #
Instance details Defined in Miso.Runtime Methods (+) :: EventSource -> EventSource -> EventSource # (-) :: EventSource -> EventSource -> EventSource # (*) :: EventSource -> EventSource -> EventSource # negate :: EventSource -> EventSource # abs :: EventSource -> EventSource # signum :: EventSource -> EventSource # fromInteger :: Integer -> EventSource #
Eq EventSource Source #
Instance details Defined in Miso.Runtime Methods (==) :: EventSource -> EventSource -> Bool # (/=) :: EventSource -> EventSource -> Bool #
ToJSVal EventSource Source #
Instance details Defined in Miso.Runtime Methods toJSVal :: EventSource -> IO JSVal Source #

type URL = MisoString Source #

URL that the WebSocket will connect to

Re-exports

data Payload value Source #

Payload is used as the potential source of data when working with EventSource

Constructors

JSON value	JSON-encoded data
BLOB Blob	Binary encoded data
TEXT MisoString	Text encoded data
BUFFER ArrayBuffer	Buffered data