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