correct-apricot

array with form composition

How can I use https://tanstack.com/form/latest/docs/framework/react/guides/arrays arrays with form composition. There are no examples of it and I cant type the useFormContext hook to make it work

Arrays | TanStack Form React Docs

TanStack Form supports arrays as values in a form, including sub-object values inside of an array. Basic Usage To use an array, you can use field.state.value on an array value: jsx function App() { co...

4 Replies

correct-apricotOP•6mo ago

import { useFormContext } from "./use-form";

export const EntryField = () => {
  const form = useFormContext();

  return (
    <form.Field name="people" mode="array">
      {(field) => {
        return (
          <div>
            {field.state.value.map((_, i) => {
              return (
                <form.Field key={i} name={`people[${i}].name`}>
                  {(subField) => {
                    return (
                      <div>
                        <label>
                          <div>Name for person {i}</div>
                          <input
                            value={subField.state.value}
                            onChange={(e) =>
                              subField.handleChange(e.target.value)
                            }
                          />
                        </label>
                      </div>
                    );
                  }}
                </form.Field>
              );
            })}
            <button
              onClick={() => field.pushValue({ name: "", age: 0 })}
              type="button"
            >
              Add person
            </button>
          </div>
        );
      }}
    </form.Field>
  );
};

import { useFormContext } from "./use-form";

export const EntryField = () => {
  const form = useFormContext();

  return (
    <form.Field name="people" mode="array">
      {(field) => {
        return (
          <div>
            {field.state.value.map((_, i) => {
              return (
                <form.Field key={i} name={`people[${i}].name`}>
                  {(subField) => {
                    return (
                      <div>
                        <label>
                          <div>Name for person {i}</div>
                          <input
                            value={subField.state.value}
                            onChange={(e) =>
                              subField.handleChange(e.target.value)
                            }
                          />
                        </label>
                      </div>
                    );
                  }}
                </form.Field>
              );
            })}
            <button
              onClick={() => field.pushValue({ name: "", age: 0 })}
              type="button"
            >
              Add person
            </button>
          </div>
        );
      }}
    </form.Field>
  );
};

this is not working as field.state.value is of type unknown

conscious-sapphire•6mo ago

I don't think useFormContext() contains the full form type, which is why they created the withForm() hoc.

rival-black•6mo ago

useFormContext is really not meant to be used like this. I'd avoid that entirely and use either withForm. Or this pattern:
https://discord.com/channels/719702312431386674/1344358153759756328/1350936904568144043

conscious-sapphire•6mo ago

Holy crap that works!! I saw that comment a couple times but couldn't wrap my head around it. I think I finally understand how to make custom hooks in react.

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array with form composition

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