airlock/README.md
2023-06-18 13:03:37 +03:00

33 lines
1.1 KiB
Markdown

# Airlock
![](res/airlock.jpeg)
## Usage
### FFI
Urbit subscriptions require [server-side event (SSE)](https://developer.mozilla.org/en-US/docs/Web/API/Server-sent_events).
Unfortunately, Elm does not provide a native implementation.
This means that we will need to use [JS FFI (aka ports)](https://guide.elm-lang.org/interop/ports.html).
#### Setting up the Elm side
You would need to declare two ports for Airlock to use:
1. `port createEventSource : String -> Cmd msg`
This sets up the SSE channel.
2. `port onEventSourceMessage : (JD.Value -> msg) -> Sub msg`
This recieves the actual messages from the SSE channel.
These two functions need to be passed to one of the functions from `Ur.Run` module.
The functions in `Ur.Run` are the same as functions from `Browser`, but have a couple of extra urbit-specific fields.
#### Setting up the JS side
The SSE JS code is neatly packed into [example/fetch-event-source.js](example/fetch-event-source.js).
All you need to do is pass them to Elm ports like in [example/script.js](example/script.js).
You can see a full working example in [example](example).