How to fetch HTTP data

Use an http.get source when you want external data to enter your app through a typed boundary and flow into ordinary signals.

Example

type User = {
    id: Int,
    name: Text
}

@source http.get "https://api.example.com/users"
signal usersResult : Signal (Result HttpError (List User))

value main =
    <Window title="Users">
        <Box orientation="vertical" spacing={12} marginTop={16} marginBottom={16} marginStart={16} marginEnd={16}>
            <Button label="Refresh" onClick={usersResult.run} />
            <show when={usersResult.loading}>
                <Spinner />
            </show>
            <show when={usersResult.error}>
                <Label text="Loading failed" />
            </show>
            <match on={usersResult.success}>
                <case pattern={Some users}>
                    <Label text={"Users: {length users}"} />
                    <Box orientation="vertical" spacing={6}>
                        <each of={users} as={user} key={user.id}>
                            <Label text={user.name} />
                        </each>
                    </Box>
                </case>
            </match>
        </Box>
    </Window>

export main

Why this shape works

1. @source http.get ... declares the outside-world boundary.
2. usersResult.run is a first-class retry signal, so the button stays a normal event hook.
3. usersResult.loading, usersResult.success, and usersResult.error expose the common request states directly.
4. The UI stays declarative: it branches on typed carriers instead of running a callback chain.

Common variations

• Need stale successful data to survive a later failure? Fold the raw Result stream through aivi.async.AsyncTracker.
• Need a typed client from an OpenAPI spec? Use OpenAPI source guide.
• Need periodic refresh? Add a timer source or explicit refreshOn signal; usersResult.run still stays available.