redux saga 选择器，如何从 saga 访问状态?

问题描述

之前有人问过类似的问题，但答案对我没有任何帮助.

Similar questions have been asked before, but the answers have not been of any help to me.

redux 中的选择器是什么?

如何获得来自 redux-saga 函数内的 state/store 的东西?

我认为我有不同的设置，因为我似乎无法从我的 saga 访问状态.

I think that I have a different setup since I cannot seem to be able to access state from my saga.

我尝试过:

const getList = store => store;
const getList = state=> state;

这些都返回 undefined.

我的商店看起来像这样...

My store looks like this...

export default function createStoreWithMiddleware() {
    const sagaMiddleware = createSagaMiddleware();
    const loggerMiddleware = createLogger();
    const middleware = [sagaMiddleware, loggerMiddleware];
    const persistedState = localStorage.getItem('reduxState') ? JSON.parse(localStorage.getItem('reduxState')) : {};

    const store = createStore(reducer, persistedState, compose(
        applyMiddleware(...middleware)
    ));

    store.subscribe(() => {
        localStorage.setItem('reduxState', JSON.stringify(store.getState()));
    });

    sagaMiddleware.run(rootSaga);

    return store;
}

我想访问我在这个传奇中的列表:

And I want to access my list in this saga:

function* selectTender(action) {
    try {
        const response = yield Api.getTenderById(action.payload);
        yield put({type: 'SELECT_TENDER_SUCCEEDED', currentTender: response});
        const list = yield select(getList);
        yield put({type: 'FETCH_CHAPTERS', chaptersList: list, tenderId: response.id});
    } catch (err) {
        yield put({type: 'SELECT_TENDER_FAILED', message: err.message});
    }
}

export function* watchSelectTender(){
    yield takeEvery('SELECT_TENDER', selectTender);
}

但就像我说的，state 和 store 都是未定义的.

But like I said, both state and store are undefined.

那么，我如何在传奇中访问我的商店(或州)?

So, how do I access my store (or state) in the saga?

推荐答案

为此您将不得不使用选择器.我举一个简单的例子.创建文件 selectors.js 并添加您要从商店中选择的字段，如下所示.

You will have to use selectors for that. I'll give a simple example.Create a file selectors.js and add the fields you want to select from your store, as shown below.

export const username = (state) => state.user.name;

然后在你的传奇中，将选择器导入为，

Then in your saga, import the selectors as,

import * as selectors from './selectors';

当你在你的传奇中需要 username 时，你可以简单地做，

and when you require username in your saga, you can simply do,

import {select} from 'redux-saga/effects';
...
...
function *sampleSaga(params) {
   const username = yield select(selectors.username);
}

sampleSaga 中的常量 username 现在将保存来自 state 的用户名值.

the constant username in sampleSaga will now hold the username value from state.

这篇关于redux saga 选择器，如何从 saga 访问状态?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！