Question

我是redux的新手，所以试图弄清楚身份验证用例的简单示例。此代码的Web版本从localstorage获取初始状态，并设置为localstorage。将此示例转换为react-native意味着localstorage更改为异步并返回promise的AsyncStorage。

如何在reducer中处理异步初始值设定项？

import { AsyncStorage } from 'react-native';
import {
  LOGIN_REQUEST, LOGIN_SUCCESS, LOGIN_FAILURE, LOGOUT_SUCCESS,
} from '../actions/login';


const initialState = {
  isFetching: false,
  token: null, // AsyncStorage.getItem('token'),
  profile: null, // AsyncStorage.getItem('profile'),
  isLoggedIn: false,
  errorMessage: null,
};

// The auth reducer. The starting state sets authentication
// based on a token in asyncstorage. In addition we would also null
// the token if we check that it's expired
export default (state = initialState, action) => {
  switch (action.type) {
    case LOGIN_REQUEST:
      return Object.assign({}, state, {
        isFetching: true,
        isLoggedIn: false,
        token: null,
        user: null,
        errorMessage: '',
      });
    case LOGIN_SUCCESS:
      // todo set the async
      // AsyncStorage.multiSet(['token', 'profile'], [action.token, action.profile])
      return Object.assign({}, state, {
        isFetching: false,
        isLoggedIn: true,
        token: action.token,
        user: action.profile,
        errorMessage: '',
      });
    case LOGIN_FAILURE:
      return Object.assign({}, state, {
        isFetching: false,
        isLoggedIn: false,
        token: null,
        errorMessage: action.message,
      });
    case LOGOUT_SUCCESS:
      // AsyncStorage.multiRemove(['token', 'profile'])
      return Object.assign({}, state, {
        isFetching: true,
        isLoggedIn: false,
        token: null,
      });
    default:
      return state;
  }
};

Answer 1

创建操作创建者，以便从AsyncStorage中获取初始数据。当您的应用加载时，您可以使用密钥token或profile来发送操作（您可以在根组件的componentDidMount中执行此操作）。

// create similar actions creators for 'setItem' and 'multiSet' ops
export function loadLocalData(key) {
  return {
    types: [LOAD_LOCAL_DATA, LOAD_LOCAL_DATA_SUCCESS, LOAD_LOCAL_DATA_FAIL]
    asyncStoragePromise: () => AsyncStorage.getItem(key),
    key,
  }
}

现在为AsyncStorage操作创建middleware。创建store时确保applyMiddleware。

中间件最常见的用例是支持异步没有太多样板代码或对库的依赖的动作像Rx。它通过让您再发送异步操作来实现正常行动。

export default function asyncStorageMiddleware() {
  return ({ dispatch, getState }) => next => (action) => {
    if (typeof action === 'function') {
      return action(dispatch, getState);
    }

    const { asyncStoragePromise, types, ...rest } = action;

    if (!asyncStoragePromise) {
      return next(action);
    }

    const [REQUEST, SUCCESS, FAILURE] = types;

    next({ ...rest, type: REQUEST });

    const actionPromise = asyncStoragePromise();
    actionPromise
      .then(result => next({ ...rest, result, type: SUCCESS }))
      .catch(error => next({ ...rest, error, type: FAILURE }));

    return actionPromise;
  };
}

最后这是 initialState ：

const initialState = {
  isFetching: false,
  token: null,
  profile: null,
  isLoggedIn: false,
  errorMessage: null,
  localLoadErr: '',
};

和 redurs ：

LOAD_LOCAL_DATA_SUCCESS:
  return {
    ...state,
    [action.key]: action.result,
  };
  break;

LOAD_LOCAL_DATA_FAIL:
  return {
    ...state,
    localLoadErr: action.error,
  };
  break;

如何在reducer

1 个答案: