zod-class

This is a small utility library to accompany Zod that enables Types and Schemas to be defined in one line by creating a Class.

Installation

npm install zod-class

Usage

1. Define a new class

import z from "zod";
import { Z } from "zod-class";

// define a class using a zod schema
export class Hello extends Z.class({
  name: z.string(),
}) {
  get getMessage() {
    return `hello ${name}`
  }
}

const hello = new Hello({
  hello: "sam",
});

2. Parse a value to an instance of a ZodClass

const hello = Hello.parse(someVal)

// use method on the instance 
const message = hello.getMessage();

3. Extend a class

export class World extends Hello.extend({
  world: z.string()
}) {}

const world = new World({
  hello: "world",
  world: "hello"
});

4. Access A ZodClass's property to re-use in other schemas

import { z } from "zod";
import { Z } from "zod-class";

export class Product extends Z.class({
  id: z.string().brand<"ProductId">,
  price: z.number().min(1)
}) {}

export class Order extends Z.class({
  id: z.string().brand<"OrderId">,
  productId: Product.shape.id // 👈 Re-using the branded type `id` from `Product` class 
}) {}


Product.Id // 👈 Properties are also available in friendly pascal case directly on the class constructor

Why?

It can be annoying to always have redundant declarations for types and schemas:

1. the z.object declaration
2. the derived type using z.infer

interface HelloSchema extends z.infer<typeof HelloSchema> {}
const HelloSchema = z.object({
  key: z.string(),
});

zod-class enables this to be achieved in a single line.

It also provides a class that can be instantiated and methods added to.

export class Person extends Z.class({
  firstName: z.string(),
  lastName: z.string(),
}) {
  get fullName() {
    return `${this.firstName} ${this.lastName}`;
  }
}

Workarounds

Creating a class that adequately sub-types a Zod Schema is difficult because of how Zod is implemented. zod-class covers the most common use-cases but there are holes.

If you encounter a problem with type errors, you can always workaround it with the schema() method.

For example, if you have a function that expects a ZodType<T>:

function createDTO<T>(schema: ZodType<T>): DTO<T>;

And a class, User, constructed with Z.class:

class User extends Z.class({
  username: z.string()
}) {}

You should be able to just pass User in

const UserDTO = createDTO(User);

In some cases, this can error. To workaround, call User.schema() instead:

const UserDTO = createDTO(User.schema());

See relevant issue: #17

2. nullish will not create a schema that returns an instance of the ZodClass

ZodClass does not provide a type-safe implementation of schema.nullish().

User.nullish().parse(value) 

This will not return an instance of User:

{ username: string } | null | undefined

Workaround with User.schema()

User.schema().nullish().parse(value) // User | null | undefined