reducer: any function with the signature (state, action) -> newState (ie, any function that could be used as an argument to Array.prototype.reduce)root reducer: the reducer function that is actually passed as the first argument to createStore. This is the only part of the reducer logic that must have the (state, action) -> newState signature.slice reducer: a reducer that is being used to handle updates to one specific slice of the state tree, usually done by passing it to combineReducerscase function: a function that is being used to handle the update logic for a specific action. This may actually be a reducer function, or it may require other parameters to do its work properly.higher-order reducer: a function that takes a reducer function as an argument, and/or returns a new reducer function as a result (such as combineReducers, or redux-undo)

irst and foremost, combineReducers is simply a utility function to simplify the most common use case when writing Redux reducers.

functions should be relatively short and ideally only do one specific thing

Redux itself does not care about how your application's folders and files are structured. However, co-locating logic for a given feature in one place typically makes it easier to maintain that code.Because of this, we recommend that most applications should structure files using a "feature folder" approach (all files for a feature in the same folder) or the "ducks" pattern (all Redux logic for a feature in a single file), rather than splitting logic across separate folders by "type" of code (reducers, actions, etc).

When a React component dispatches actions, how can another service catch the actions, accumulate and group them, then redispatch a single action?

you can make the component a container component by wrapping it in a higher-order component returned by connect().

wrapping your entire application in a <Provider> component

React Redux now offers a set of hook APIs as an alternative to the existing connect() Higher Order Component. These APIs allow you to subscribe to the Redux store and dispatch actions, without having to wrap your components in connect()

Notice that none of these changed anything about how Redux works. We're still creating a Redux store, dispatching action objects that describe "what happened", and returning updated state using a reducer function. Also, notice that the Redux Toolkit functions can be used no matter what approach was used to build the UI, since they just handle the "plain Redux store" part of the code. Our example used the store with a "vanilla JS" UI, but we could use this same store with React, Angular, Vue, or any other UI layer.

And no longer requires you to install the redux-thunk or redux-devtools-extension dependencies.

The Redux Toolkit package is intended to be the standard way to write Redux logic. It was originally created to help address three common concerns about Redux:"Configuring a Redux store is too complicated""I have to add a lot of packages to get Redux to do anything useful""Redux requires too much boilerplate code"

To do that, the react-redux library comes with 2 things: a component called Provider, and a function called connect.

Reducer Rule #2: Reducers must be pure functions.

automatically handle all other action types by returning the current state

in most apps, you won't need to use them yourself - createSlice is all you need.

The whole state of your app is stored in an object tree inside a single store. The only way to change the state tree is to emit an action, an object describing what happened. To specify how the actions transform the state tree, you write pure reducers.

Instead of allowing any and all components to fetch and manipulate data, which can make debugging pretty much suck, we want to implement a pattern that's in line with the Single Responsibility Principle, and that keeps our code DRY.

This section introduces how React components using the ag-Grid Data Table can take advantage of a Redux store to simplify state management.

The most common signature for HOCs looks like this: // React Redux's `connect` const ConnectedComment = connect(commentSelector, commentActions)(CommentList); What?! If you break it apart, it’s easier to see what’s going on. // connect is a function that returns another function const enhance = connect(commentListSelector, commentListActions); // The returned function is a HOC, which returns a component that is connected // to the Redux store const ConnectedComment = enhance(CommentList); In other words, connect is a higher-order function that returns a higher-order component!

I was so fed up of the mega amounts of boilerplate with Redux and the recommendation of keeping your data loading at view level. It seems to me that things like this, with components being responsible for their own data, is the way to go in the future.

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这样可以方便的进行单元测试，不需要模拟Api.fetch函数的具体返回结果。

const shopItemsSelector = state => state.shop.items const taxPercentSelector = state => state.shop.taxPercent

const subtotalSelector = createSelector( shopItemsSelector, items => items.reduce((acc, item) => acc + item.value, 0) )

I’ve personally seen two big benefits after adopting this strict separation in production apps. The first is that teams can more easily reuse the Presentation Components because they are nothing more than html/css. Over time this will allow the team to amass a great component library that is more composable allowing even greater code sharing across the organization. The second benefit is that teams can more easily upgrade the infrastructure that powers data flow throughout the application. Because this code is isolated in the Container Components we don’t need to untangle the plumbing code from the html/css that displays it. So you want to swap your global store for an ember service? No problem! We just modify the entry point in the Container Components and the data still flows down to any Presentational Components like it did before the refactor.

Therefore we've built https://github.com/salsita/redux-side-effects which is at least "somehow" trying to simulate the Continuations with Effect handlers approach. The idea is very simple, if reducer was generator then you could simply yield side effects and return mutated app state. So the only condition is to turn all your reducers into function* and use yield* whenever you want to compose them.

All kinds of frameworks and architectures have state. In Ember apps and Backbone apps, state is in Models. In Angular apps, state is often in Factories and Services. In most Flux implementations, it is in Stores. How does Redux differ from these?

You can call store.dispatch(action) from anywhere in your app, including components and XHR callbacks, or even at scheduled intervals.

Now todoApp just gives it the slice of the state to manage, and todos knows how to update just that slice.

If your head boiled from reading the above section, imagine what it was like to write it.