compute

The Statety.compute function is used to create computed state derived from multiple dependency keys. Computed state updates automatically whenever any of its dependencies change, allowing you to combine multiple pieces of state into a single cohesive value.

TypeScript Signature

Statety.compute<T extends readonly any[], U>(
  keyName: string,
  deps: { [K in keyof T]: AnyStatetyKey<T[K]> },
  fn: (values: { [K in keyof T]: T[K] }) => U
): ComputedStatetyKey<U>

Example

Creating a Computed State

import { Statety } from "statety";

const USER_KEY = Statety.create<{ username: string; role: string }>("user", {
  username: "guest",
  role: "visitor",
});

const ORDERS_KEY = Statety.create<Order[]>("orders", []);

// Compute the number of orders for the current user
const USER_ORDERS_COUNT_KEY = Statety.compute(
  "user-orders-count",
  [USER_KEY, ORDERS_KEY],
  ([user, orders]) => {
    if (!user || !orders) return 0;
    return orders.filter(order => order.user === user.username).length;
  }
);

const count = Statety.read(USER_ORDERS_COUNT_KEY);
console.log(count); // Output: 0

Notes

• Computed state cannot be set manually; it updates automatically when any dependency changes.
• It is ideal for combining multiple pieces of state into one computed value.
• Dependencies can include any combination of basic, derived, or other computed state keys.