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@craft-ts
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craftEffect#

An effect that can resolve craft dependencies with yield*.

Use it when a side effect needs a service. Not as a way to sync state — if a value is a function of another, derive it with computed instead of writing it from an effect.

Import#

typescript
import { craftEffect } from '@craft-ts/core';
typescript
craftUse(craftEffect('myEffect', function* () {
  const counter = yield* Counter();
  // do some stuff
}));

Resource triggers#

In generator code, primitive triggers are yieldable and must be consumed with yield*:

typescript
function* submit(term: string) {
  yield* searchQuery.call(term);
  yield* saveMutation.mutate({ term });
  yield* validateProcess.method(term);
}

Imperative triggers from ordinary UI callbacks remain valid:

typescript
button({ click: () => saveMutation.mutate({ term: input() }) }, 'Save');

Do not use those triggers as dependencies of a craftEffect. Prefer a declarative params signal, a source$, or a mutation/query insertion. The craft-ts/no-imperative-craft-resource-trigger rule also follows a craftGen, so wrapping the call does not bypass the restriction:

typescript
const triggerSearch = craftGen(function* (term: string) {
  yield* searchQuery.call(term);
});

craftUse(craftEffect('load', function* () {
  yield* triggerSearch(input()); // forbidden: indirect imperative trigger
}));

Use a reactive query instead when the data depends on a signal:

typescript
const user = yield* query('user', {
    params: userId,
    loader: ({ params }) => fetchUser(params),
  });

See Also#

  • craftComputed

  • craftMethod

  • Local state — deriving instead of writing from an effect

  • Architecture rules — assertCraftEffectNoNetwork when an effect calls HTTP or a mutation, assertCraftEffectNoImperativeSync when it writes a state/source$ or triggers a query/mutation

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