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Form Arrays ‚Äč

Because HouseForm supports nested field values, you might want to try to build an array out like this:

tsx
import { Field, Form } from "houseform";

export const Example = () => (
  <Form
    onSubmit={(values) => {
      alert("Form was submitted with: " + JSON.stringify(values));
    }}
  >
    {() => (
      <Field<Array<{ name: string }>>
        name="people"
        initialValue={[{ name: "Corbin" }]}
      >
        {({ value, setValue }) => (
          <>
            {value.map((person, i) => (
              <Field<string> name={`people[${i}].name`} key={`person-${i}`}>
                {({ value, setValue }) => (
                  <input
                    value={value}
                    onChange={(e) => setValue(e.target.value)}
                  />
                )}
              </Field>
            ))}
          </>
        )}
      </Field>
    )}
  </Form>
);

This works and tracks an array on submission, but has a few problems:

  • No easy utility to add, move, insert, or do other helper functions on arrays
  • A ref on the Field<Array> does not track the current value of the array
  • Memory usage is bloated due to duplicated values between array values
  • Changing the array values do not persist the field values

For these reasons, we introduce a specific APIs for arrays of fields: FieldArray and FieldArrayItem.

tsx
import { FieldArray, FieldArrayItem, Form } from "houseform";

export const Example = () => (
  <Form
    onSubmit={(values) => {
      alert("Form was submitted with: " + JSON.stringify(values));
    }}
  >
    {() => (
      <>
        <FieldArray<{ name: string }>
          ref={test}
          name="people"
          initialValue={[{ name: "Corbin" }]}
        >
          {({ value, add }) => (
            <>
              {value.map((person, i) => (
                <FieldArrayItem<string>
                  name={`people[${i}].name`}
                  key={`person-${i}`}
                >
                  {({ value, setValue }) => {
                    return (
                      <input
                        value={value}
                        onChange={(e) => setValue(e.target.value)}
                      />
                    );
                  }}
                </FieldArrayItem>
              ))}
              <button onClick={() => add({ name: "Other" })}>Add</button>
            </>
          )}
        </FieldArray>
        <button onClick={test1}>Submit</button>
      </>
    )}
  </Form>
);

Here, we replace the top-level array tracking Field with FieldArray and the sub-fields with Field.

Please note that, unlike field, FieldArrayItem does not store its own value. Instead, it uses a context provided by FieldArray to track the value inside of FieldArray.

As a result, you may want to wrap the components inside of the FieldArrayItem within a React.memo to avoid re-renders.