Function useMutation

Apollo-style mutation hook — idle until mutate() is called. Returns { data, loading, failure, mutate, reset, cancel, called }.

mutate() never rejects — it resolves with the parsed response body on success, or undefined on any failure. failure narrows on kind: 'transport' (no response exists — abort, timeout, connection lost) carries error: FetchError; 'http' (server answered outside 2xx) carries response, the resolved ok-false FetchResponse.

const { mutate, loading, failure } = useMutation<User>(api, 'post', '/users', {
    emitOnSuccess: 'users.created',
}, observer);

const user = await mutate({ name: 'Alice' });

if (!user) {
    if (failure?.kind === 'http') console.error(failure.response.status);
    if (failure?.kind === 'transport') console.error(failure.error.message);
    return;
}