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Merge pull request #2795 from sanderhahn/master
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Add docstrings to store
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Rich-Harris authored May 21, 2019
2 parents 931c080 + 832259f commit 57141a9
Showing 1 changed file with 45 additions and 0 deletions.
45 changes: 45 additions & 0 deletions src/store.ts
Original file line number Diff line number Diff line change
@@ -1,32 +1,64 @@
import { run_all, noop, safe_not_equal, is_function } from './internal/utils';

/** Callback to inform of a value updates. */
type Subscriber<T> = (value: T) => void;

/** Unsubscribes from value updates. */
type Unsubscriber = () => void;

/** Callback to update a value. */
type Updater<T> = (value: T) => T;

/** Cleanup logic callback. */
type Invalidater<T> = (value?: T) => void;

/** Start and stop notification callbacks. */
type StartStopNotifier<T> = (set: Subscriber<T>) => Unsubscriber | void;

/** Readable interface for subscribing. */
export interface Readable<T> {
/**
* Subscribe on value changes.
* @param run subscription callback
* @param invalidate cleanup callback
*/
subscribe(run: Subscriber<T>, invalidate?: Invalidater<T>): Unsubscriber;
}

/** Writable interface for both updating and subscribing. */
export interface Writable<T> extends Readable<T> {
/**
* Set value and inform subscribers.
* @param value to set
*/
set(value: T): void;

/**
* Update value using callback and inform subscribers.
* @param updater callback
*/
update(updater: Updater<T>): void;
}

/** Pair of subscriber and invalidator. */
type SubscribeInvalidateTuple<T> = [Subscriber<T>, Invalidater<T>];

/**
* Creates a `Readable` store that allows reading by subscription.
* @param value initial value
* @param start start and stop notifications for subscriptions
*/
export function readable<T>(value: T, start: StartStopNotifier<T>): Readable<T> {
return {
subscribe: writable(value, start).subscribe,
};
}

/**
* Create a `Writable` store that allows both updating and reading by subscription.
* @param value initial value
* @param start start and stop notifications for subscriptions
*/
export function writable<T>(value: T, start: StartStopNotifier<T> = noop): Writable<T> {
let stop: Unsubscriber;
const subscribers: Array<SubscribeInvalidateTuple<T>> = [];
Expand Down Expand Up @@ -68,11 +100,20 @@ export function writable<T>(value: T, start: StartStopNotifier<T> = noop): Writa
return { set, update, subscribe };
}

/** One or more `Readable`s. */
type Stores = Readable<any> | [Readable<any>, ...Array<Readable<any>>];

/** One or more values from `Readable` stores. */
type StoresValues<T> = T extends Readable<infer U> ? U :
{ [K in keyof T]: T[K] extends Readable<infer U> ? U : never };

/**
* Derived value store by synchronizing one or more readable stores and
* applying an aggregation function over its input values.
* @param stores input stores
* @param fn function callback that aggregates the values
* @param initial_value when used asynchronously
*/
export function derived<T, S extends Stores>(
stores: S,
fn: (values: StoresValues<S>, set?: Subscriber<T>) => T | Unsubscriber | void,
Expand Down Expand Up @@ -129,6 +170,10 @@ export function derived<T, S extends Stores>(
});
}

/**
* Get the current value from a store by subscribing and immediately unsubscribing.
* @param store readable
*/
export function get<T>(store: Readable<T>): T {
let value: T | undefined;
store.subscribe((_: T) => value = _)();
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