T
TanStack•2y ago
deep-jade

Can I use a selector for the `store.subscribe` method?

In my project I am building a form wizard with multiple steps. Each step should report to a progress bar as soon as it becomes valid. For this I have two approaches right now. The first one is via form.subscribe: 
const Validator = ({ isValid }: ValidatorProps) => {
  useEffect(() => {
    if (isValid) {
      console.log("form is valid");
    } else {
      console.log("form is invalid");
    }
  }, [isValid]);

  return <p>{isValid ? "form is valid" : "form is invalid"}</p>;
};

// usage:
<form.Subscribe
    selector={(state) => [state.canSubmit]}
    children={([canSubmit]) => {
      return <Validator isValid={canSubmit} />;
    }}
  />
const Validator = ({ isValid }: ValidatorProps) => {
  useEffect(() => {
    if (isValid) {
      console.log("form is valid");
    } else {
      console.log("form is invalid");
    }
  }, [isValid]);

  return <p>{isValid ? "form is valid" : "form is invalid"}</p>;
};

// usage:
<form.Subscribe
    selector={(state) => [state.canSubmit]}
    children={([canSubmit]) => {
      return <Validator isValid={canSubmit} />;
    }}
  />
What I like here is that I am only notified if the canSubmit state changes and nothing else, but it seems to be a bit too complicated for what I want to achieve. My other component is working with the store.subscribe method: 
const HookValidator = () => {
  const formApi = useFormApi();
  const store = formApi.store;
  const [isValid, setIsValid] = useState(store.state.canSubmit);

  store.subscribe(() => {
    if (store.state.canSubmit) {
      console.log("form is valid");
      setIsValid(true);
    } else {
      console.log("form is invalid");
      setIsValid(false);
    }
  });

  return <p>{isValid ? "form is valid" : "form is invalid"}</p>;
};
const HookValidator = () => {
  const formApi = useFormApi();
  const store = formApi.store;
  const [isValid, setIsValid] = useState(store.state.canSubmit);

  store.subscribe(() => {
    if (store.state.canSubmit) {
      console.log("form is valid");
      setIsValid(true);
    } else {
      console.log("form is invalid");
      setIsValid(false);
    }
  });

  return <p>{isValid ? "form is valid" : "form is invalid"}</p>;
};
This is logging on each state change and not only on the state.canSubmit property. Can I select the value I want to subscribe to with store.subscribe like I can with form.Subscribe? Thanks in advance for your help!
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