Extend previous schema

Sometimes it's useful to define an action "template" with a base schema and then extend it with additional properties. This can be done inside the schema method by passing an async function that has the previous schema as its argument. See the example below:

"use server";

import { actionClient } from "@/lib/safe-action";
import { z } from "zod";

const schema = z.object({
  username: z.string(),
});

const myAction = actionClient
  .schema(schema)
  .schema(async (prevSchema) => {
    // Here we extend the previous schema with `password` property.
    return prevSchema.extend({ password: z.string() });
  })
  .schema(async (prevSchema) => {
    // Here with `age` property.
    return prevSchema.extend({ age: z.number().positive() });
  })
  // `parsedInput` will be an object with `username`, `password` and `age` properties.
  .action(async ({ parsedInput: { username, password, age } }) => { 
    // Do something useful here...
  });

Note that if you don't use prevSchema inside the schema method, the previous schema(s) will be overwritten.