In this context, thunks and endpoints are identical, so I will just talk about thunks throughout this guide.

There are two ways to call a thunk within another thunk.

Dispatch the thunk as an action #

Features:

• Non-blocking
• Thunk is still controlled by supervisor
• Works identical to dispatch(action)

1import { put } from "starfx";
2const fetchMailboxes = api.get("/mailboxes");
3const fetchMail = thunks.create("fetch-mail", function* (ctx, next) {
4  yield* put(fetchMailboxes());
5});

This is the equivalent of using useDispatch in your view. As a result, it is also controlled by the thunk's supervisor task. If that thunk has a supervisor that might drop the middleware stack from activating (e.g. takeLeading or timer) then it might not actually get called. Further, this operation completes immediately, it does not wait for the thunk to complete before moving to the next yield point.

If you want to make a blocking call to the thunk and wait for it to complete then you want to call the thunk's middleware stack directly.

Call the middleware stack directly #

Features:

• Blocking
• Middleware stack guarenteed to run
• Does not go through supervisor task

What do we mean by "middleware stack"? That is the stack of functions that you define for a thunk. It does not include the supervisor task that manages the thunk. Because a supervisor task could drop, pause, or delay the execution of a thunk, we need a way to escape hatch out of it and just call the middleware stack directly.

 1import { parallel, put } from "starfx";
 2// imaginary schema
 3import { schema } from "./schema";
 4
 5const fetchMailboxes = api.get("/mailboxes");
 6const fetchMessages = api.get<{ id: string }>("/mailboxes/:id/messages");
 7const fetchMail = thunks.create("fetch-mail", function* (ctx, next) {
 8  const boxesCtx = yield* fetchMailboxes.run();
 9  if (!boxesCtx.json.ok) {
10    return;
11  }
12
13  const boxes = yield* select(schema.mailboxes.selectTableAsList);
14  const group = yield* parallel(boxes.map((box) => {
15    return fetchMessages.run({ id: box.id });
16  }));
17  const messages = yield* select(schema.messages.selectTableAsList);
18  console.log(messages);
19});