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This function takes an initial value and a yup schema. This function returns Field object.


The field() takes 3 parameters and some generic type parameters:

declare function field<T>(
  value: T | Ref<T>,
  schema?: FieldSchema,
  validateOptions?: ValidateOptions
): Field<T, T>;
declare function field<T, U extends T>(
  value: T | Ref<T>,
  schema?: FieldSchema,
  validateOptions?: ValidateOptions
): Field<T, U>;

1. value Required

  • Pass an initial value like such as string, number, boolean, and string[] types.


Internally the value is made reactive by shallowRef(). To use a Ref other than shallowRef(), pass a Ref object instead.

import { ref } from "vue";

const point = field(
  ref({ x: 0, y: 0, z: 0 }),
    .shape({ x: yup.number().required(),  y: yup.number().required(), z: yup.number().required() })
      test: ({ x, y, z }) => x ** 2 + y ** 2 + z ** 2 <= 1,
      message: "Specify the inside of the unit ball.",

2. schema Optional

  • Pass a yup schema or a function that returns a yup schema.
    • If you pass a function, you can refer to $value of other fields.


Even when using v-model.number, changing the input box to empty may set "" (an empty string). This causes the validation with yup.NumberSchema to output an undesirable error message:

try {
} catch (e) {
  console.log(e.message); // this must be a `number` type, but the final value was: `NaN` (cast from the value `""`).

To avoid the above, empty strings are validated as undefined if yup.NumberSchema is specified.

const age = field(20, yup.number().required());

// Equivalent to changing <input type="number" v-model.number="age.$value"> to empty
age.$value = "";

console.log(age.$error.message); // this is a required field


Since validateSync() is used internally, Async tests are not available.

3. validateOptions Optional

  • Pass { abortEarly: false } if all validation errors by the yup schema are required.

T Optional

  • Pass the type of $value explicitly like ref<T>().

U Optional

  • Pass the preferred type as the result of toObject().

Details of Field object

$value property

  • The field value that can be set to v-model.

$error property Readonly

  • Returns a result of validating $value reactively with the yup schema.
    • If $value is invalid, yup.ValidationError is returned.
    • If $value is valid, undefined is returned.

$errorMessages property Readonly

  • Returns an error messages array (string[]) reactively as well as $error property.
    • If abortEarly is false, it can return more than one element.

$label property Readonly

  • Returns the label of the yup schema.
    • For example, if you pass yup.number().label("Age"), you will obtain "Age".
    • If the schema you passed is a function, the function is evaluated once when the object is created.