Support for custom validation

Is there any plan to support custom validation? It could be of the form: z.string().validate(someValidationFunction).

That would be a great help to build advanced schemas.

This could also take the form of custom types, but for now, z.ZodType / z.ZodTypeDef not being exposed as part of the API make it a hack IMO.

[jjhiggz]

I don’t see it in the documentation on this for some reason, but I’m wondering if this got added somewhere.

I was poking around and found a .custom on the z object, and got it to work by doing the following.

const isValidPhoneNumber = (phonenumber: string) => phonenumber.length > 3

const SignupValidation = z.object({
  email: z.string().email(),
  cell: z
   // Input 1 seems to be your validator function, which should return true or false depending on the input
   // Input 2 seems to be how you control what messages show up
    .custom(isValidPhoneNumber, { message: "Not a valid phone number" })
    .transform(parseInt),
})

Obviously that’s not a real phone validation, but the logic works for implementing a custom validation. You can ignore the transform key, and also the email in the validation. I just like providing a little extra context with these answers.

Update

I think this approach using refine is probably better because then zod can first verify the type, then refine that type. As a side bonus you can use the input value to make your error message which seems cool

    const isPhoneNumber = (ph: string) => ph.length > 4;
    const phoneNumberSchema = z.string().refine(isPhoneNumber, (val) => ({
      message: `${val} is not a valid phone number`,
    }));

It also means you can infer the schema type which you can not do with z.custom

[colinhacks]

This is doable. I’m working on a big rewrite currently (probably gonna be Zoe 2) and I’ll include this in that release.