InstanceOf

Use ft.InstanceOf to validate an unknown value is an instance of a class.

Simple Class

import * as ft from "funtypes";

export class User {
  public readonly name: string;
  constructor(name: string) {
    this.name = name;
  }
}
export const UserSchema = ft.InstanceOf(User);
// => ft.Codec<User>


// ✅ Valid instance of User:
assert.deepEqual(
  UserSchema.parse(new User("Forbes Lindesay")),
  new User("Forbes Lindesay"),
);

// 🚨 Correct shape, but not an instance of the class:
assert.throws(() => UserSchema.parse({ name: "Forbes Lindesay" }));

// 🚨 Invalid value:
assert.throws(() => UserSchema.parse("A"));