vant/src/composables/use-link-field.ts

import { watch, inject } from 'vue';
import { FIELD_KEY } from '../field';

export function useLinkField(getValue: () => unknown) {
  const field = inject(FIELD_KEY, null) as any;

  if (field && !field.childFieldValue.value) {
    field.childFieldValue.value = getValue;

    watch(getValue, () => {
      field.resetValidation();
      field.validateWithTrigger('onChange');
    });
  }
}