useStatetyCompute

The useStatetyCompute hook allows you to compute a value derived from multiple state keys inside a React component. It acts like a component-level version of Statety.compute, automatically updating whenever any of the source keys change. You can also provide additional dependencies to dynamically influence the computation.

TypeScript Signature

export function useStatetyCompute<T extends readonly any[], U>(
  keys: { [K in keyof T]: AnyStatetyKey<T[K]> },
  fn: (values: { [K in keyof T]: T[K] | null }) => U,
  deps?: any[]
): U

Parameters

• keys – An array of Statety keys (basic, derived, or computed) that the computed value depends on.
• fn – A function that receives the current values of all keys and returns the computed result.
• deps - Optional array of additional dependencies that will trigger recalculation when changed.

Returns

• U – The value returned by the computation function.

Example

Computing a Value from Multiple Keys

import { useState } from "react";
import { Statety, useStatetyCompute } from "statety";

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

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

function UserOrdersCount() {
  const [minQuantity, setMinQuantity] = useState(1);

  const count = useStatetyCompute([USER_KEY, ORDERS_KEY], ([user, orders]) => {
    if (!user || !orders) return 0;
    return orders.filter(order => order.user === user.username && order.quantity >= minQuantity).length;
  }, [minQuantity]); // Component-level dependency

  return (
    <div>
      <p>User orders with minimum quantity {minQuantity}: {count}</p>
      <button onClick={() => setMinQuantity(minQuantity + 1)}>Increase Min Quantity</button>
    </div>
  );
}

Notes

• useStatetyCompute automatically subscribes to all keys provided, so the component re-renders whenever any dependency changes.
• The optional deps array allows external parameters to trigger recomputation.
• Works with basic, derived, and computed keys.
• Use this hook when dealing with data or calculations that depend on component-level parameters (e.g., user input, local state) in React.