javascript - 使用 redux saga 时出错，take(patternOrChannel) : argument 8 is not valid channel or a valid pattern

Question

我正在尝试使用 redux saga 库来捕获一些操作，但在运行该应用程序时出现此错误:

index.js:2178 uncaught at rootSaga at rootSaga at projectSaga at watchFetchRequest at takeEvery Error: take(patternOrChannel): argument 8 is not valid channel or a valid pattern at take (http://localhost:3000/static/js/bundle.js:84689:9) at takeEvery (http://localhost:3000/static/js/bundle.js:85993:94) at createTaskIterator (http://localhost:3000/static/js/bundle.js:85179:17) at runForkEffect (http://localhost:3000/static/js/bundle.js:85583:24) at runEffect (http://localhost:3000/static/js/bundle.js:85468:872) at next (http://localhost:3000/static/js/bundle.js:85348:9) at proc (http://localhost:3000/static/js/bundle.js:85303:3) at runForkEffect (http://localhost:3000/static/js/bundle.js:85587:19) at runEffect (http://localhost:3000/static/js/bundle.js:85468:872) at http://localhost:3000/static/js/bundle.js:85677:14 at Array.forEach () at runAllEffect (http://localhost:3000/static/js/bundle.js:85676:10) at runEffect (http://localhost:3000/static/js/bundle.js:85468:413) at next (http://localhost:3000/static/js/bundle.js:85348:9) at proc (http://localhost:3000/static/js/bundle.js:85303:3) at runForkEffect (http://localhost:3000/static/js/bundle.js:85587:19) at runEffect (http://localhost:3000/static/js/bundle.js:85468:872) at http://localhost:3000/static/js/bundle.js:85677:14 at Array.forEach () at runAllEffect (http://localhost:3000/static/js/bundle.js:85676:10) at runEffect (http://localhost:3000/static/js/bundle.js:85468:413) at next (http://localhost:3000/static/js/bundle.js:85348:9) at proc (http://localhost:3000/static/js/bundle.js:85303:3) at runSaga (http://localhost:3000/static/js/bundle.js:85858:76) at Object../src/store/ReduxRoot.tsx (http://localhost:3000/static/js/bundle.js:95823:16) at webpack_require (http://localhost:3000/static/js/bundle.js:679:30) at fn (http://localhost:3000/static/js/bundle.js:89:20) at Object../src/index.tsx (http://localhost:3000/static/js/bundle.js:95325:75) at webpack_require (http://localhost:3000/static/js/bundle.js:679:30) at fn (http://localhost:3000/static/js/bundle.js:89:20) at Object.0 (http://localhost:3000/static/js/bundle.js:96424:18) at webpack_require (http://localhost:3000/static/js/bundle.js:679:30) at ./node_modules/@babel/runtime/helpers/arrayWithoutHoles.js.module.exports (http://localhost:3000/static/js/bundle.js:725:37) at http://localhost:3000/static/js/bundle.js:728:10

这是传奇代码:

import { all, call, fork, put, takeEvery } from 'redux-saga/effects';
import {  ActionType, Action, SearchCriteria } from '../model/types';
import { searchProjectsError, searchProjectsCompleted } from '../actions/projects';
import { API_URL } from '../../config';
// import axios from 'axios';

function callApi(method: string, url: string, path: string, data?: any) {
    return fetch(url  + path, {
      method,
      headers: {'Content-Type': 'application/json; charset=utf-8', 'Access-Control-Allow-Origin': '*'},
      body: JSON.stringify(data)
    }).then(res => res.json());
  }

// Here we use `redux-saga` to trigger actions asynchronously. `redux-saga` uses something called a
// "generator function", which you can read about here:
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function*

function* handleFetch(action: Action<SearchCriteria>) {
  try {
    // To call async functions, use redux-saga's `call()`.
    const res = yield call(callApi, 'get', API_URL , '/api/DocumentLoader/GetProjects/', action.payload);

    if (res.error) {
      yield put(searchProjectsError(res.error));
    } else {
      yield put(searchProjectsCompleted(res));
    }
  } catch (err) {
    if (err instanceof Error) {
      yield put(searchProjectsError(err.stack!));
    } else {
      yield put(searchProjectsError('An unknown error occured.'));
    }
  }
}

// This is our watcher function. We use `take*()` functions to watch Redux for a specific action
// type, and run our saga, for example the `handleFetch()` saga above.
function* watchFetchRequest() {
  yield takeEvery(ActionType.SEARCH_PROJECTS, handleFetch); // I think the error is here
}

// We can also use `fork()` here to split our saga into multiple watchers.
function* projectSaga() {
  yield all([fork(watchFetchRequest)]);
}

export default projectSaga;

我已经尝试在 SO 中找到答案，但我唯一能找到的是 this post ，但 ActionType 已导出。我认为问题出在 handleFetch 函数的参数上

这是 Action :

export function searchProjects(criterias: SearchCriteria): Action<SearchCriteria> {
    return {
        type: ActionType.SEARCH_PROJECTS,
        payload: criterias
    };
}

另一件事可能是我当时在编写 saga 中间件时做错了什么:

const sagaMiddleware = createSagaMiddleware();

var middleware = applyMiddleware(logger, thunk, sagaMiddleware);

if (process.env.NODE_ENV === 'development') {
    middleware = composeWithDevTools(middleware);
}

// Here we use `redux-saga` to trigger actions asynchronously. `redux-saga` uses something called a
// "generator function", which you can read about here:
// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/function*
export function* rootSaga() {
    yield all([fork(projectSaga)]);
  }
// running the root saga, and return the store object.
 sagaMiddleware.run(rootSaga);

我还尝试从 handleFetch 中删除 action 参数，但错误仍在发生

Answer 1

我发现了错误，问题出在 ActionType 枚举的定义上。它没有为每个操作分配一个字符串值。

export const enum ActionType {

// Projects
SEARCH_PROJECT,
SEARCH_PROJECTS_COMPLETED,
SEARCH_PROJECTS_ERROR,

}

这解决了问题:

export const enum ActionType {

// Projects
SEARCH_PROJECTS= '@@projects/SEARCH_PROJECTS',
SEARCH_PROJECTS_COMPLETED= '@@projects/SEARCH_PROJECTS_COMPLETED',
SEARCH_PROJECTS_ERROR= '@@projects/SEARCH_PROJECTS_ERROR',

}