javascript - 如何将 reduce-reducers 与 combineReducers 一起使用

Question

所以，我试图在另一个 reducer 中使用一个 reducer 的一些状态，我寻找了一个解决方案，似乎 reduce-reducers 包确实做到了这一点，但这是我的问题...

我有以下 rootReducer.js 文件，我在其中导入所有 reducer 并将它们与 combineReducers 组合在一起，就像这样......

import { combineReducers } from "redux";
import globalReducer from "./globalReducer";
import booksReducer from "../features/books/booksReducer";
import categriesReducer from "../features/categories/categoriesReducer";
import authorsReducer from "../features/authors/authorsReducer";

const rootReducer = combineReducers({
    global: globalReducer,
    books: booksReducer,
    categories: categriesReducer,
    authors: authorsReducer
});

export default rootReducer;

现在我想在 books reducer 中使用来自 authors reducer 的一些状态，如何使用 reduce-reducers 包实现？

Answer 1

reduce-reducers 的工作方式类似于 reducers 的“合并”:

const reducer = (state = 0, action) => {
    switch (action.type) {
        case 'ADD':
            return state + action.value;
        case 'MULTIPLE':
            return state * action.value;
        default:
            return state;
    }
};

同样可以用reduce-reducers来写:

const addReducer = (state = 0, action) => {
    switch (action.type) {
        case 'ADD':
            return state + action.value;
        default:
            return state;
    }
};
const multipleReducer = (state = 0, action) => {
    switch (action.type) {
        case 'MULTIPLE':
            return state * action.value;
        default:
            return state;
    }
};

const reducer = reduceReducers(addReducer, multipleReducer, 0);

所以在你的任务中，这意味着你应该重写你的 authorsReducer 和 booksReducer 以便它获得整个状态作为第一个参数，而不仅仅是它自己的 authors 部分:

const before = (state = [], action) => {
    switch (action.type) {
        case `NEW_BOOK`:
            return state.concat([action.book]);
        default:
            return state;
    }
}

const now = (state = {}, action) => {
    switch (action.type) {
        case `NEW_BOOK`:
            return {
                ...state,
                books: state.books.concat([action.book]),
            };
        default:
            return state;
    }
}

但是!我认为这不是您真正想要的。

还有另一个包可以满足您的需求 combine-section-reducers

它允许您从任何其他 reducer 访问根状态:

const before = (state = [], action) => {
    switch (action.type) {
        case `NEW_BOOK`:
            return state.concat([action.book]);
        default:
            return state;
    }
}

const now = (state = [], action, rootState) => {
    switch (action.type) {
        case `NEW_BOOK`:
            return state.concat([{
                ...action.book,
                author: rootState.authors[action.book.authorId],
            }]);
        default:
            return state;
    }
}