I have a field where I want the value to either be optional OR have the field have a minimum length of 4
.
I’ve tried the following:
export const SocialsSchema = z.object({ myField: z.optional(z.string().min(4, "Please enter a valid value")), });
This passes if I used a value like: "good"
, but if I’ve got an empty value then it fails.
How do I correctly implement a constraint using zod schemas to make an optional value with a minimum constraint if the value is not empty?
Is it possible to do this without using regex or a regex solution the only way?
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Answer
In your case, you consider ""
to be the same as undefined
(i.e.: when the string is empty, it’s like there’s no string at all).
It’s implementable in Zod this way:
import { z } from "zod"; import { strict as assert } from "node:assert"; // `myString` is a string that can be either optional (undefined or missing), // empty, or min 4 const myString = z .union([z.string().length(0), z.string().min(4)]) .optional() .transform(e => e === "" ? undefined : e); const schema = z.object({ test: myString }); assert( schema.parse({}).test === undefined ); // missing string assert( schema.parse({ test: undefined }).test === undefined ); // string is undefined assert( schema.parse({ test: "" }).test === undefined ); // string is empty assert( schema.parse({ test: "1234" }).test === "1234" ); // string is min 4 // these successfully fail assert( schema.safeParse({ test: "123" }).success !== true ); assert( schema.safeParse({ test: 3.14 }).success !== true );