Today I Learned

A Hashrocket project

Formik's Validation Schema As A Function

The most straightforward way to use Formik’s validationSchema is to provide it with a Yup object defining your form’s validations.

const MyComponent = withFormik({
  // ...

  validationSchema: yup.object().shape({
    email: yup.string().required(),
    feedback: yup.string().required(),
  }),
  
  // ...
})(MyForm);

There may be a point at which you need access to the props being passed to MyComponent in order to construct the proper set of validations. Formik supports this by allowing validationSchema to be a function.

const MyComponent = withFormik({
  // ...

  validationSchema: (props) => {
    let emailSchema;
    if(props.allowAnonymous) {
      emailSchema = yup.string();
    } else {
      emailSchema = yup.string().required();
    }

    return yup.object().shape({
      email: emailSchema,
      feedback: yup.string().required(),
    });
  },
  
  // ...
})(MyForm);

When validationSchema is a function, its first argument is the set of props passed to that component.

Looking for help? At Hashrocket, our JavaScript experts launch scalable, performant apps on the Web, Android and iOS. Contact us and find out how we can help you.