PayloadFetchStoreclass

new PayloadFetchStore<P, R>(payload: P | typeof NONE, value: R | typeof NONE, callback?: PayloadFetchCallback<P, R>, debounce = 0)

Param	Type
`payload`	`P` `typeof NONE`	The initial payload for the store. required
`value`	`R` `typeof NONE`	The initial value for the store, or `NONE` if it does not have one yet. required
`callback`	`PayloadFetchCallback<P, R>`	An optional callback that, if set, will be called with the current payload when the `fetch()` method is invoked to fetch the next value.
`debounce`	`unknown`	Delay in milliseconds before the fetch is triggered after a payload change. `busy` becomes `true` immediately; the actual fetch waits for the debounce period to expire. If the payload changes again before the delay expires the previous fetch is cancelled and the timer resets. Defaults to `0`

Return
`PayloadFetchStore<P, R>`	Store that fetches its values from a remote source by sending it a payload.

Property	Type
`.payload`	`Store<P>`	Store keeping the current payload to send to the fetch on send. - New payloads can be set using `this.payload.value` required readonly

Store that fetches its values from a remote source by sending it a payload.

Holds the current payload in a nested this.payload store; setting this.payload.value triggers a fresh fetch.
Optionally debounces fetches so rapid payload changes only result in a single request.

A FetchStore whose fetch is driven by a payload. PayloadFetchStore<P, R> holds an inner .payload store; whenever the payload changes, any in-flight fetch is cancelled and a fresh one starts with the new payload.

This is the base class for EndpointStore in the shelving/api module — the payload is the endpoint's request payload.

Usage

Pass an initial payload, an initial value (or NONE), and a callback that receives the current payload:

import { PayloadFetchStore, NONE } from "shelving/store";

const store = new PayloadFetchStore<string, User>(
  "u_1",
  NONE,
  async (id, signal) => (await fetch(`/api/users/${id}`, { signal })).json(),
);

const first = await store.next; // fetches for "u_1"

// Changing the payload cancels the previous fetch and starts a new one.
store.payload.value = "u_2";

Pass a fourth debounce argument (milliseconds) to delay the fetch after a payload change — rapid changes reset the timer, so only the final payload is fetched.

Examples

const store = new PayloadFetchStore("dave", NONE, async (name, signal) => (await fetch(`/api/user/${name}`, { signal })).json());
store.payload.value = "sam"; // triggers a new fetch