Type checks in Typescript with Zod

Question

I have the code:

import { z } from "zod";

interface f {
   tmp: number;
}

How can I now check that object like { tmp: 123 } has same structure as f?

Answer 1

You can use Zod to create a schema for your interface f and then use the parse method to check if an object adheres to that schema.

import { z, ZodError } from "zod";

interface f {
 tmp: number;
}

const schema = z.object({
 tmp: z.number()
});

const myObject = { tmp: 123 };

try {
 const validatedObject: f = schema.parse(myObject);
 console.log("Object is valid:", validatedObject);
} catch (error) {
 if (error instanceof ZodError) {
  console.error("Object is not valid:", error.errors);
 } else {
  throw error;
 }
}

So in this example, schema.parse(myObject) will throw a ZodError if myObject doesn't match the structure defined by the f interface. If the object is valid, it will be assigned to validatedObject.

---

Update:

The z.object method allows you to dynamically create a schema based on the structure of the f interface.

import { z, ZodError } from "zod";
interface f {
  tmp: number;
}
const schema = z.object(
  Object.fromEntries(
    Object.entries<Record<string, z.ZodType<any, any, any>>>({
      tmp: z.number(),
    })
  )
);

const myObject = { tmp: 123 };

try {
  const validatedObject: f = schema.parse(myObject);
  console.log("Object is valid:", validatedObject);
} catch (error) {
  if (error instanceof ZodError) {
    console.error("Object is not valid:", error.errors);
  } else {
    throw error;
  }
}

This way you don't have to manually list all the fields in z.object. This code dynamically creates a schema based on the fields defined in the f interface.