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本文作者：霜序
前言
为何讲这个内容？以为后续大家会使用 redux-toolkit，资产上周做了 redux-toolkit 的升级顺便了解了相关内容，产出了这篇文章。
另外补齐一下在 React 数据流这个知识板块的完整性。
在之前的周分享中已经分享过了React 中的数据流，react-redux 的一些实现，redux 中中间件的实现，以及 Mobx 的使用以及丐版实现。
对于 Redux 本身尚未涉及，趁着使用 redux-toolkit 的机会一起了解一下 Redux 的实现。
Redux-Toolkit
Redux-Toolkit 是 基于 Redux 的二次封装，开箱即用的 Redux 工具，比 Redux 更加简单方便。
🚧 Why to use Redux-Toolkit?
- "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"
Toolkit 使用
Redux 该有的概念，Toolkit 其实都拥有的，只是他们使用的方式不同，例如 reducer / actions 等等，在 Toolkit 中都是随处可见的。
configureStore
创建 store，代码内部还是调用的 Redux 的 createStore 方法
const store = configureStore({
reducer: {
counter: counterReducer,
user: userReducer,
},
});createAction + createReducer
- createAction
创建 Redux 中的 action 创建函数
function createAction(type, prepareAction?)redux 中 action 的创建以及使用
const updateName = (name: string) => ({ type: "user/UPDATE_NAME", name });
const updateAge = (age: number) => ({ type: "user/UPDATE_AGE", age });Toolkit 中 action 的创建以及使用
// 第一种
const updateName = createAction<{ name: string }>("user/UPDATE_NAME");
const updateAge = createAction<{ age: number }>("user/UPDATE_AGE");
updateName(); // { type: 'user/UPDATE_NAME', payload: undefined }
updateName({ name: "FBB" }); // { type: 'user/UPDATE_NAME', payload: { name: 'FBB' } }
updateAge({ age: 18 });
// 第二种
const updateName = createAction("user/UPDATE_NAME", (name: string) => ({
payload: {
name,
},
}));
const updateAge = createAction("user/UPDATE_AGE", (age: number) => ({
payload: {
age,
},
}));
updateName("FBB");
updateAge(18);- createReducer
创建 Redux reducer 的函数
💡 createReducer 使用 Immer 库，可以在 reducer 中直接对状态进行修改，而不需要手动编写不可变性的逻辑
Redux 中 reducer 的创建
export const userReducer = (
state = initialUserState,
action: { type: string; [propName: string]: any }
) => {
switch (action.type) {
case "user/UPDATE_NAME":
return { ...state, name: action.name };
case "user/UPDATE_AGE":
return { ...state, age: action.age };
default:
return state;
}
};Toolkit 中 reducer 的创建
export const userReducer = createReducer(initialUserState, (builder) => {
builder
.addCase(updateAge, (state, action) => {
state.age = action.payload.age;
})
.addCase(updateName, (state, action) => {
state.name = action.payload.name;
});
});toolkit 提供的 createAction 和 createReducer 能够帮我们简化 Redux 中一些模版语法，但是整体的使用还是差不多的，我们依旧需要 action 文件和 reducer 文件，做了改善但是不多。
redux demo toolkit createReducer demo
createSlice
接受初始状态、reducer 函数对象和 slice name 的函数，并自动生成与 reducer 和 state 对应的动作创建者和动作类型
const userSlice = createSlice({
name: "user",
initialState: {
age: 22,
name: "shuangxu",
},
reducers: {
updateName: (state, action: PayloadAction<string>) => {
state.name = action.payload;
},
updateAge: (state, action: PayloadAction<number>) => {
state.age = action.payload;
},
},
})使用 createSlice 创建一个分片，每一个分片代表某一个业务的数据状态处理。在其中可以完成 action 和 reducer 的创建。
export const userSliceName = userSlice.name;
export const { updateAge, updateName } = userSlice.actions;
export const userReducer = userSlice.reducer;
const store = configureStore({
reducer: {
[counterSliceName]: counterReducer,
[userSliceName]: userReducer,
},
});在 Toolkit 中直接使用 createSlice 更加方便，能够直接导出 reducer 和 action，直接在一个方法中能够获取到对应内容不在需要多处定义。
Redux 源码实现
简单的状态管理
所谓的状态其实就是数据，例如用户中的 name
let state = {
name: "shuangxu"
}
// 使用状态
console.log(state.name)
// 更改状态
state.name = "FBB"上述代码中存在问题，当我们修改了状态之后无法通知到使用状态的函数，需要引入发布订阅模式来解决这个问题
const state = {
name: "shuangxu",
};
const listeners = [];
const subscribe = (listener) => {
listeners.push(listener);
};
const changeName = (name) => {
state.name = name;
listeners.forEach((listener) => {
listener?.();
});
};
subscribe(() => console.log(state.name));
changeName("FBB");
changeName("LuckyFBB");在上述代码中，我们已经实现了更改变量能够通知到对应的监听函数。但是上述代码并不通用，需要将公共方法封装起来。
const createStore = (initialState) => {
let state = initialState;
let listeners = [];
const subscribe = (listener) => {
listeners.push(listener);
return () => {
listeners = listeners.filter((fn) => fn !== listener);
};
};
const changeState = (newState) => {
state = { ...state, ...newState };
listeners.forEach((listener) => {
listener?.();
});
};
const getState = () => state;
return {
subscribe,
changeState,
getState,
};
};
// example
const { getState, changeState, subscribe } = createStore({
name: "shuangxu",
age: 19,
});
subscribe(() => console.log(getState().name, getState().age));
changeState({ name: "FBB" }); // FBB 19
changeState({ age: 26 }); // FBB 26
changeState({ sex: "female" });约束状态管理器
上述的实现能够更改状态和监听状态的改变。但是上述改变 state 的方式过于随便了，我们可以任意修改 state 中的数据，changeState({ sex: "female" })，即使 sex 不存在于 initialState 中，所以我们需要约束只能够修改 name/age 属性
通过一个 plan 函数来规定UPDATE_NAME和UPDATE_AGE方式更新对应属性
const plan = (state, action) => {
switch (action.type) {
case "UPDATE_NAME":
return {
...state,
name: action.name,
};
case "UPDATE_AGE":
return {
...state,
age: action.age,
};
default:
return state;
}
};更改一下 createStore 函数
const createStore = (plan, initialState) => {
let state = initialState;
let listeners = [];
const subscribe = (listener) => {
listeners.push(listener);
return () => {
listeners = listeners.filter((fn) => fn !== listener);
};
};
const changeState = (action) => {
state = plan(state, action);
listeners.forEach((listener) => {
listener?.();
});
};
const getState = () => state;
return {
subscribe,
changeState,
getState,
};
};
const { getState, changeState, subscribe } = createStore(plan, {
name: "shuangxu",
age: 19,
});
subscribe(() => console.log(getState().name, getState().age));
changeState({ type: "UPDATE_NAME", name: "FBB" });
changeState({ type: "UPDATE_AGE", age: "28" });
changeState({ type: "UPDATE_SEX", sex: "female" });代码中的 plan 就是 redux 中的 reducer，changeState 就是 dispatch。
拆分 reducer
reducer 做的事情比较简单，接收 oldState，通过 action 更新 state。
但是实际项目中可能存在不同模块的 state，如果都把 state 的执行计划写在同一个 reducer 中庞大有复杂。
因此在常见的项目中会按模块拆分不同的 reducer，最后在一个函数中将 reducer 合并起来。
const initialState = {
user: { name: "shuangxu", age: 19 },
counter: { count: 1 },
};
// 对于上述 state 我们将其拆分为两个 reducer
const userReducer = (state, action) => {
switch (action.type) {
case "UPDATE_NAME":
return {
...state,
name: action.name,
};
case "UPDATE_AGE":
return {
...state,
age: action.age,
};
default:
return state;
}
};
const counterReducer = (state, action) => {
switch (action.type) {
case "INCREMENT":
return {
count: state.count + 1,
};
case "DECREMENT":
return {
...state,
count: state.count - 1,
};
default:
return state;
}
};
// 整合 reducer
const combineReducers = (reducers) => {
// 返回新的 reducer 函数
return (state = {}, action) => {
const newState = {};
for (const key in reducers) {
const reducer = reducers[key];
const preStateForKey = state[key];
const nextStateForKey = reducer(preStateForKey, action);
newState[key] = nextStateForKey;
}
return newState;
};
};代码跑起来！！
const reducers = combineReducers({
counter: counterReducer,
user: userReducer,
});
const store = createStore(reducers, initialState);
store.subscribe(() => {
const state = store.getState();
console.log(state.counter.count, state.user.name, state.user.age);
});
store.dispatch({ type: "UPDATE_NAME", name: "FBB" }); // 1 FBB 19
store.dispatch({ type: "UPDATE_AGE", age: "28" }); // 1 FBB 28
store.dispatch({ type: "INCREMENT" }); // 2 FBB 28
store.dispatch({ type: "DECREMENT" }); // 1 FBB 28拆分 state
在上一节的代码中，我们 state 还是定义在一起的，会造成 state 树很庞大，在项目中使用的时候我们都在 reducer 中定义好 initialState 的。
在使用 createStore 的时候，我们可以不传入 initialState，直接使用store = createStore(reducers)。因此我们要对这种情况作处理。
拆分 state 和 reducer 写在一起。
const initialUserState = { name: "shuangxu", age: 19 };
const userReducer = (state = initialUserState, action) => {
switch (action.type) {
case "UPDATE_NAME":
return {
...state,
name: action.name,
};
case "UPDATE_AGE":
return {
...state,
age: action.age,
};
default:
return state;
}
};
const initialCounterState = { count: 1 };
const counterReducer = (state = initialCounterState, action) => {
switch (action.type) {
case "INCREMENT":
return {
count: state.count + 1,
};
case "DECREMENT":
return {
...state,
count: state.count - 1,
};
default:
return state;
}
};更改 createStore 函数，可以自动获取到每一个 reducer 的 initialState
const createStore = (reducer, initialState = {}) => {
let state = initialState;
let listeners = [];
const subscribe = (listener) => {
listeners.push(listener);
return () => {
listeners = listeners.filter((fn) => fn !== listener);
};
};
const dispatch = (action) => {
state = reducer(state, action);
listeners.forEach((listener) => {
listener?.();
});
};
const getState = () => state;
// 仅仅用于获取初始值
dispatch({ type: Symbol() });
return {
subscribe,
dispatch,
getState,
};
};dispatch({ type: Symbol() })代码能够实现如下效果：
- createStore 的时候，一个不匹配任何 type 的 action，来触发
state = reducer(state, action) - 每个 reducer 都会进到 default 项，返回 initialState
Redux-Toolkit 源码实现
configureStore
接受一个含有 reducer 的对象作为参数，内部调用 redux 的 createStore 创建出 store
import { combineReducers, createStore } from "redux";
export function configureStore({ reducer }: any) {
const rootReducer = combineReducers(reducer);
const store = createStore(rootReducer);
return store;
}createAction
const updateName = createAction<string>("user/UPDATE_NAME");
const updateName = createAction("user/UPDATE_NAME", (name: string) => ({
payload: {
name,
},
}));
updateName("FBB");通过上面的示例，能够分析出来 createAction 返回的是一个函数，接受第一个参数 type 返回{ type: 'user/UPDATE_NAME', payload: undefined }；对于具体的 payload 值需要传入第二个参数来改变
export const createAction = (type: string, preAction?: Function) => {
function actionCreator(...args: any[]) {
if (!preAction)
return {
type,
payload: args[0],
};
const prepared = preAction(...args);
if (!prepared) {
throw new Error("prepareAction did not return an object");
}
return {
type,
payload: prepared.payload,
};
}
actionCreator.type = type;
return actionCreator;
};createReducer
export const userReducer = createReducer(initialUserState, (builder) => {
builder
.addCase(updateAge, (state, action) => {
state.age = action.payload.age;
})
.addCase(updateName, (state, action) => {
state.name = action.payload.name;
});
});每一个 reducer 都是一个函数(state = initialState, action) => {}，因此 createReducer 返回值为函数
通过一个 createReducer 函数，内部还需要知道每一个 action 对应的操作
import { produce as createNextState } from "immer";
export const createReducer = (
initialState: any,
builderCallback: (builder: any) => void
) => {
const actionsMap = executeReducerBuilderCallback(builderCallback);
return function reducer(state = initialState, action: any) {
const caseReducer = actionsMap[action.type];
if (!caseReducer) return state;
return createNextState(state, (draft: any) =>
caseReducer(draft, action)
);
};
};
// 通过 createReducer 的第二个参数，构建出 action 对应的操作方法
export const executeReducerBuilderCallback = (
builderCallback: (builder: any) => void
) => {
const actionsMap: any = {};
const builder = {
addCase(typeOrActionCreator: any, reducer: any) {
const type =
typeof typeOrActionCreator === "string"
? typeOrActionCreator
: typeOrActionCreator.type;
actionsMap[type] = reducer;
return builder;
},
};
builderCallback(builder);
return actionsMap;
};createSlice
const counterSlice = createSlice({
name: "counter",
initialState: {
count: 1,
},
reducers: {
increment: (state: any) => {
state.count += 1;
},
decrement: (state: any) => {
state.count -= 1;
},
},
});
const counterSliceName = counterSlice.name;
const { increment, decrement } = counterSlice.actions;
const counterReducer = counterSlice.reducer;createSlice 返回的是一个对象{ name, actions, reducer }，接受{ name, initialState, reducers }三个参数。通过 reducers 中相关参数得到对应的 actions 和 reducer。
在 createSlice 中主要还是靠 createAction 和 createReducer 方法。通过 name 和 reducers 的每一个属性拼接成为 action.type，调用 createReducer 遍历 reducers 的属性添加 case
import { createAction } from "./createAction";
import { createReducer } from "./createReducer";
export default function createSlice({ name, initialState, reducers }: any) {
const reducerNames = Object.keys(reducers);
const actionCreators: any = {};
const sliceCaseReducersByType: any = {};
reducerNames.forEach((reducerName) => {
const type = `${name}/${reducerName}`;
const reducerWithPrepare = reducers[reducerName];
actionCreators[reducerName] = createAction(type);
sliceCaseReducersByType[type] = reducerWithPrepare;
});
function buildReducer() {
return createReducer(initialState, (builder) => {
for (let key in sliceCaseReducersByType) {
builder.addCase(key, sliceCaseReducersByType[key]);
}
});
}
return {
name,
actions: actionCreators,
reducer: (state: any, action: any) => {
const _reducer = buildReducer();
return _reducer(state, action);
},
};
}总结
在本文讲解了 Redux-Toolkit 基础使用，从 redux 的源码出发解析了 redux-toolkit 的源码，从源码中也能够看出来 toolkit 的实现是基于 redux 来实现的，且使用上也大同小异，无破坏性变更。
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