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stepancar/improved redux.d.ts

Created March 8, 2018 11:15
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improved redux.d.ts
/**
* An *action* is a plain object that represents an intention to change the
* state. Actions are the only way to get data into the store. Any data,
* whether from UI events, network callbacks, or other sources such as
* WebSockets needs to eventually be dispatched as actions.
*
* Actions must have a `type` field that indicates the type of action being
* performed. Types can be defined as constants and imported from another
* module. It's better to use strings for `type` than Symbols because strings
* are serializable.
*
* Other than `type`, the structure of an action object is really up to you.
* If you're interested, check out Flux Standard Action for recommendations on
* how actions should be constructed.
*/
export interface Action {
type: any;
}
/**
* An Action type which accepts any other properties.
* This is mainly for the use of the `Reducer` type.
* This is not part of `Action` itself to prevent users who are extending `Action.
* @private
*/
export interface AnyAction extends Action {
// Allows any extra properties to be defined in an action.
[extraProps: string]: any;
}
/* reducers */
/**
* A *reducer* (also called a *reducing function*) is a function that accepts
* an accumulation and a value and returns a new accumulation. They are used
* to reduce a collection of values down to a single value
*
* Reducers are not unique to Redux—they are a fundamental concept in
* functional programming. Even most non-functional languages, like
* JavaScript, have a built-in API for reducing. In JavaScript, it's
* `Array.prototype.reduce()`.
*
* In Redux, the accumulated value is the state object, and the values being
* accumulated are actions. Reducers calculate a new state given the previous
* state and an action. They must be *pure functions*—functions that return
* the exact same output for given inputs. They should also be free of
* side-effects. This is what enables exciting features like hot reloading and
* time travel.
*
* Reducers are the most important concept in Redux.
*
* *Do not put API calls into reducers.*
*
* @template S State object type.
*/
export type Reducer<S> = (state: S, action: AnyAction) => S;
/**
* Object whose values correspond to different reducer functions.
*/
type ReducersMapObject<S> = {
[P in keyof S]: Reducer<S[P]>;
}
/**
* Turns an object whose values are different reducer functions, into a single
* reducer function. It will call every child reducer, and gather their results
* into a single state object, whose keys correspond to the keys of the passed
* reducer functions.
*
* @template S Combined state object type.
*
* @param reducers An object whose values correspond to different reducer
* functions that need to be combined into one. One handy way to obtain it
* is to use ES6 `import * as reducers` syntax. The reducers may never
* return undefined for any action. Instead, they should return their
* initial state if the state passed to them was undefined, and the current
* state for any unrecognized action.
*
* @returns A reducer function that invokes every reducer inside the passed
* object, and builds a state object with the same shape.
*/
export function combineReducers<S>(reducers: ReducersMapObject<S>): Reducer<S>;
/* store */
/**
* A *dispatching function* (or simply *dispatch function*) is a function that
* accepts an action or an async action; it then may or may not dispatch one
* or more actions to the store.
*
* We must distinguish between dispatching functions in general and the base
* `dispatch` function provided by the store instance without any middleware.
*
* The base dispatch function *always* synchronously sends an action to the
* store's reducer, along with the previous state returned by the store, to
* calculate a new state. It expects actions to be plain objects ready to be
* consumed by the reducer.
*
* Middleware wraps the base dispatch function. It allows the dispatch
* function to handle async actions in addition to actions. Middleware may
* transform, delay, ignore, or otherwise interpret actions or async actions
* before passing them to the next middleware.
*/
export interface Dispatch<S> {
<A extends Action>(action: A): A;
}
/**
* Function to remove listener added by `Store.subscribe()`.
*/
export interface Unsubscribe {
(): void;
}
/**
* A store is an object that holds the application's state tree.
* There should only be a single store in a Redux app, as the composition
* happens on the reducer level.
*
* @template S State object type.
*/
export interface Store<S> {
/**
* Dispatches an action. It is the only way to trigger a state change.
*
* The `reducer` function, used to create the store, will be called with the
* current state tree and the given `action`. Its return value will be
* considered the **next** state of the tree, and the change listeners will
* be notified.
*
* The base implementation only supports plain object actions. If you want
* to dispatch a Promise, an Observable, a thunk, or something else, you
* need to wrap your store creating function into the corresponding
* middleware. For example, see the documentation for the `redux-thunk`
* package. Even the middleware will eventually dispatch plain object
* actions using this method.
*
* @param action A plain object representing “what changed”. It is a good
* idea to keep actions serializable so you can record and replay user
* sessions, or use the time travelling `redux-devtools`. An action must
* have a `type` property which may not be `undefined`. It is a good idea
* to use string constants for action types.
*
* @returns For convenience, the same action object you dispatched.
*
* Note that, if you use a custom middleware, it may wrap `dispatch()` to
* return something else (for example, a Promise you can await).
*/
dispatch: Dispatch<S>;
/**
* Reads the state tree managed by the store.
*
* @returns The current state tree of your application.
*/
getState(): S;
/**
* Adds a change listener. It will be called any time an action is
* dispatched, and some part of the state tree may potentially have changed.
* You may then call `getState()` to read the current state tree inside the
* callback.
*
* You may call `dispatch()` from a change listener, with the following
* caveats:
*
* 1. The subscriptions are snapshotted just before every `dispatch()` call.
* If you subscribe or unsubscribe while the listeners are being invoked,
* this will not have any effect on the `dispatch()` that is currently in
* progress. However, the next `dispatch()` call, whether nested or not,
* will use a more recent snapshot of the subscription list.
*
* 2. The listener should not expect to see all states changes, as the state
* might have been updated multiple times during a nested `dispatch()` before
* the listener is called. It is, however, guaranteed that all subscribers
* registered before the `dispatch()` started will be called with the latest
* state by the time it exits.
*
* @param listener A callback to be invoked on every dispatch.
* @returns A function to remove this change listener.
*/
subscribe(listener: () => void): Unsubscribe;
/**
* Replaces the reducer currently used by the store to calculate the state.
*
* You might need this if your app implements code splitting and you want to
* load some of the reducers dynamically. You might also need this if you
* implement a hot reloading mechanism for Redux.
*
* @param nextReducer The reducer for the store to use instead.
*/
replaceReducer(nextReducer: Reducer<S>): void;
}
/**
* A store creator is a function that creates a Redux store. Like with
* dispatching function, we must distinguish the base store creator,
* `createStore(reducer, preloadedState)` exported from the Redux package, from
* store creators that are returned from the store enhancers.
*
* @template S State object type.
*/
type StoreCreator = {
<S>(reducer: Reducer<S>, enhancer?: StoreEnhancer<S>): Store<S>;
<S>(reducer: Reducer<S>, preloadedState: S, enhancer?: StoreEnhancer<S>): Store<S>;
}
/**
* A store enhancer is a higher-order function that composes a store creator
* to return a new, enhanced store creator. This is similar to middleware in
* that it allows you to alter the store interface in a composable way.
*
* Store enhancers are much the same concept as higher-order components in
* React, which are also occasionally called “component enhancers”.
*
* Because a store is not an instance, but rather a plain-object collection of
* functions, copies can be easily created and modified without mutating the
* original store. There is an example in `compose` documentation
* demonstrating that.
*
* Most likely you'll never write a store enhancer, but you may use the one
* provided by the developer tools. It is what makes time travel possible
* without the app being aware it is happening. Amusingly, the Redux
* middleware implementation is itself a store enhancer.
*/
export type StoreEnhancer<S> = (next: StoreEnhancerStoreCreator<S>) => StoreEnhancerStoreCreator<S>;
export type GenericStoreEnhancer = <S>(next: StoreEnhancerStoreCreator<S>) => StoreEnhancerStoreCreator<S>;
export type StoreEnhancerStoreCreator<S> = (reducer: Reducer<S>, preloadedState?: S) => Store<S>;
/**
* Creates a Redux store that holds the state tree.
* The only way to change the data in the store is to call `dispatch()` on it.
*
* There should only be a single store in your app. To specify how different
* parts of the state tree respond to actions, you may combine several
* reducers
* into a single reducer function by using `combineReducers`.
*
* @template S State object type.
*
* @param reducer A function that returns the next state tree, given the
* current state tree and the action to handle.
*
* @param [preloadedState] The initial state. You may optionally specify it to
* hydrate the state from the server in universal apps, or to restore a
* previously serialized user session. If you use `combineReducers` to
* produce the root reducer function, this must be an object with the same
* shape as `combineReducers` keys.
*
* @param [enhancer] The store enhancer. You may optionally specify it to
* enhance the store with third-party capabilities such as middleware, time
* travel, persistence, etc. The only store enhancer that ships with Redux
* is `applyMiddleware()`.
*
* @returns A Redux store that lets you read the state, dispatch actions and
* subscribe to changes.
*/
export const createStore: StoreCreator;
/* middleware */
export interface MiddlewareAPI<S> {
dispatch: Dispatch<S>;
getState(): S;
}
/**
* A middleware is a higher-order function that composes a dispatch function
* to return a new dispatch function. It often turns async actions into
* actions.
*
* Middleware is composable using function composition. It is useful for
* logging actions, performing side effects like routing, or turning an
* asynchronous API call into a series of synchronous actions.
*/
export interface Middleware {
<S>(api: MiddlewareAPI<S>): (next: Dispatch<S>) => Dispatch<S>;
}
/**
* Creates a store enhancer that applies middleware to the dispatch method
* of the Redux store. This is handy for a variety of tasks, such as
* expressing asynchronous actions in a concise manner, or logging every
* action payload.
*
* See `redux-thunk` package as an example of the Redux middleware.
*
* Because middleware is potentially asynchronous, this should be the first
* store enhancer in the composition chain.
*
* Note that each middleware will be given the `dispatch` and `getState`
* functions as named arguments.
*
* @param middlewares The middleware chain to be applied.
* @returns A store enhancer applying the middleware.
*/
export function applyMiddleware(...middlewares: Middleware[]): GenericStoreEnhancer;
/* action creators */
/**
* An *action creator* is, quite simply, a function that creates an action. Do
* not confuse the two terms—again, an action is a payload of information, and
* an action creator is a factory that creates an action.
*
* Calling an action creator only produces an action, but does not dispatch
* it. You need to call the store's `dispatch` function to actually cause the
* mutation. Sometimes we say *bound action creators* to mean functions that
* call an action creator and immediately dispatch its result to a specific
* store instance.
*
* If an action creator needs to read the current state, perform an API call,
* or cause a side effect, like a routing transition, it should return an
* async action instead of an action.
*
* @template A Returned action type.
*/
export interface ActionCreator<A> {
(...args: any[]): A;
}
/**
* Object whose values are action creator functions.
*/
export interface ActionCreatorsMapObject {
[key: string]: ActionCreator<any>;
}
/**
* Turns an object whose values are action creators, into an object with the
* same keys, but with every function wrapped into a `dispatch` call so they
* may be invoked directly. This is just a convenience method, as you can call
* `store.dispatch(MyActionCreators.doSomething())` yourself just fine.
*
* For convenience, you can also pass a single function as the first argument,
* and get a function in return.
*
* @param actionCreator An object whose values are action creator functions.
* One handy way to obtain it is to use ES6 `import * as` syntax. You may
* also pass a single function.
*
* @param dispatch The `dispatch` function available on your Redux store.
*
* @returns The object mimicking the original object, but with every action
* creator wrapped into the `dispatch` call. If you passed a function as
* `actionCreator`, the return value will also be a single function.
*/
export function bindActionCreators<A extends ActionCreator<any>>(actionCreator: A, dispatch: Dispatch<any>): A;
export function bindActionCreators<
A extends ActionCreator<any>,
B extends ActionCreator<any>
>(actionCreator: A, dispatch: Dispatch<any>): B;
export function bindActionCreators<M extends ActionCreatorsMapObject>(actionCreators: M, dispatch: Dispatch<any>): M;
export function bindActionCreators<
M extends ActionCreatorsMapObject,
N extends ActionCreatorsMapObject
>(actionCreators: M, dispatch: Dispatch<any>): N;
/* compose */
type Func0<R> = () => R;
type Func1<T1, R> = (a1: T1) => R;
type Func2<T1, T2, R> = (a1: T1, a2: T2) => R;
type Func3<T1, T2, T3, R> = (a1: T1, a2: T2, a3: T3, ...args: any[]) => R;
/**
* Composes single-argument functions from right to left. The rightmost
* function can take multiple arguments as it provides the signature for the
* resulting composite function.
*
* @param funcs The functions to compose.
* @returns R function obtained by composing the argument functions from right
* to left. For example, `compose(f, g, h)` is identical to doing
* `(...args) => f(g(h(...args)))`.
*/
export function compose(): <R>(a: R) => R;
export function compose<F extends Function>(f: F): F;
/* two functions */
export function compose<A, R>(
f1: (b: A) => R, f2: Func0<A>
): Func0<R>;
export function compose<A, T1, R>(
f1: (b: A) => R, f2: Func1<T1, A>
): Func1<T1, R>;
export function compose<A, T1, T2, R>(
f1: (b: A) => R, f2: Func2<T1, T2, A>
): Func2<T1, T2, R>;
export function compose<A, T1, T2, T3, R>(
f1: (b: A) => R, f2: Func3<T1, T2, T3, A>
): Func3<T1, T2, T3, R>;
/* three functions */
export function compose<A, B, R>(
f1: (b: B) => R, f2: (a: A) => B, f3: Func0<A>
): Func0<R>;
export function compose<A, B, T1, R>(
f1: (b: B) => R, f2: (a: A) => B, f3: Func1<T1, A>
): Func1<T1, R>;
export function compose<A, B, T1, T2, R>(
f1: (b: B) => R, f2: (a: A) => B, f3: Func2<T1, T2, A>
): Func2<T1, T2, R>;
export function compose<A, B, T1, T2, T3, R>(
f1: (b: B) => R, f2: (a: A) => B, f3: Func3<T1, T2, T3, A>
): Func3<T1, T2, T3, R>;
/* four functions */
export function compose<A, B, C, R>(
f1: (b: C) => R, f2: (a: B) => C, f3: (a: A) => B, f4: Func0<A>
): Func0<R>;
export function compose<A, B, C, T1, R>(
f1: (b: C) => R, f2: (a: B) => C, f3: (a: A) => B, f4: Func1<T1, A>
): Func1<T1, R>;
export function compose<A, B, C, T1, T2, R>(
f1: (b: C) => R, f2: (a: B) => C, f3: (a: A) => B, f4: Func2<T1, T2, A>
): Func2<T1, T2, R>;
export function compose<A, B, C, T1, T2, T3, R>(
f1: (b: C) => R, f2: (a: B) => C, f3: (a: A) => B, f4: Func3<T1, T2, T3, A>
): Func3<T1, T2, T3, R>;
/* rest */
export function compose<R>(
f1: (b: any) => R, ...funcs: Function[]
): (...args: any[]) => R;
export function compose<R>(...funcs: Function[]): (...args: any[]) => R;
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