DefinitelyTyped/types/create-subscription/index.d.ts

// Type definitions for create-subscription 16.4
// Project: https://github.com/facebook/react/tree/master/packages/create-subscription
// Definitions by: Asana <https://github.com/Asana>
//                 Vincent Siao <https://github.com/vsiao>
// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
// TypeScript Version: 2.8

import * as React from "react";

export type Unsubscribe = () => any;

export interface SubscriptionConfig<S, T> {
    /**
     * Synchronously gets the value for the subscribed property.
     * Return undefined if the subscribable value is undefined,
     * Or does not support synchronous reading (e.g. native Promise).
     */
    getCurrentValue: (source: S) => T;

    /**
     * Set up a subscription for the subscribable value in props, and return an unsubscribe function.
     * Return false to indicate the property cannot be unsubscribed from (e.g. native Promises).
     * Due to the variety of change event types, subscribers should provide their own handlers.
     * Those handlers should not attempt to update state though;
     * They should call the callback() instead when a subscription changes.
     */
    subscribe: (source: S, callback: (newValue: T) => void) => Unsubscribe;
}

export interface SubscriptionProps<S, T> {
    children: (value: T) => React.ReactNode;
    source: S;
}

export interface Subscription<S, T> extends React.ComponentClass<SubscriptionProps<S, T>> {}

export function createSubscription<S, T>(config: SubscriptionConfig<S, T>): Subscription<S, T>;