如何在 react-redux 中调度页面加载操作？

Question

我必须显示一个包含大量数据的表格。有一个分页按钮，每页显示 10 条记录。我有一个名为“FETCH”的按钮，点击它的表格正在填充。如何在页面加载时加载我的表格。

action.js

import fetch from 'isomorphic-fetch';
export const ADD_BENEFICIARY = 'ADD_BENEFICIARY';
export const REMOVE_BENEFICIARY = 'REMOVE_BENEFICIARY';

export const ADD_PLAN_TO_COMPARE = 'ADD_PLAN_COMPARE';
export const REMOVE_PLAN_FROM_COMPARE = 'REMOVE_PLAN_COMPARE';
export const SHOW_PLAN_COMPARE = 'SHOW_PLAN_COMPARE';

export const NEXT_PAGE_PLAN_LIST = 'NEXT_PAGE_PLAN_LIST';
export const PREV_PAGE_PLAN_LIST = 'PREV_PAGE_PLAN_LIST';
export const REQUEST_PAGE_PLAN_LIST = 'REQUEST_PAGE_PLAN_LIST';
export const RECEIVE_PAGE_PLAN_LIST = 'RECEIVE_PAGE_PLAN_LIST';

export const showNextPageOfPlans = () => {

  return {
    type: NEXT_PAGE_PLAN_LIST
  }
}

export const showPreviousPageOfPlans = () => {

  return {
    type: PREV_PAGE_PLAN_LIST
  }
}

export const requestPageOfPlans = (startIdx, pageSize) => {

  return {
    type: REQUEST_PAGE_PLAN_LIST,
    start: startIdx,
    pageSize: pageSize
  }
}

export const receivePageOfPlans = (startIdx, json) => {

  return {
    type: RECEIVE_PAGE_PLAN_LIST,
    start: startIdx,
    plans: json
  }
}


export const fetchPlans = (startIdx, pageSize) => {

    var str = sessionStorage.getItem('formValue'); //JSON.stringify(formValues);

  return function (dispatch) {
    dispatch(requestPageOfPlans(startIdx, pageSize));
    return fetch('http://172.16.32.57:9090/alternatePlans/plans/list/', {method: 'post', body: str, headers: new Headers({'Content-Type': 'application/json'})  })
      .then(response => response.json())
      .then(json =>
        dispatch(receivePageOfPlans(startIdx, json))
      )
  }
}

reducer.js

import { REQUEST_PAGE_PLAN_LIST, RECEIVE_PAGE_PLAN_LIST,
         NEXT_PAGE_PLAN_LIST, PREV_PAGE_PLAN_LIST } from './actions';

const initialPaging = {

  startIndex: 0,
  lastIndex: 0,
  pageSize: 10
}

const paging = (state = initialCurrentPage, action) => {

  switch (action.type) {

    case NEXT_PAGE_PLAN_LIST:

      if (state.startIndex+state.pageSize <= state.lastIndex) {

        return { ...state, startIndex: state.startIndex+state.pageSize };
      }
      else {

        return state;
      }

    case PREV_PAGE_PLAN_LIST:

      if (state.startIndex-state.pageSize >= 0) {

        return { ...state, startIndex: state.startIndex-state.pageSize };
      }
      else {

        return state;
      }

    case REQUEST_PAGE_PLAN_LIST:

      return { ...state, isFetching: true };

    case RECEIVE_PAGE_PLAN_LIST:

      return { ...state, isFetching: false };

    default:
      return state;
  }

}

var initialPlans = [];

const plans = (state = initialPlans, action) => {

  switch (action.type) {

    case RECEIVE_PAGE_PLAN_LIST:
      return action.plans.plans;

    default:
      return state;
  }
}


const allReducers = (state = {}, action) => {

  let items = plans(state.plans, action);
  return {
    plans: items,
    paging: paging({ ...initialPaging, ...state.paging, lastIndex: items.length-1 }, action)
  }
}

export default allReducers;

附：我是 react-redux 的新手。官方文档很好，但给出的解释很少。

Answer 1

您可以从页面的 react 组件的 componentDidMount() 或任何有意义的地方调用它。所以在那个组件文件中：

import { requestPageOfPlans } from 'actions';
import React from 'react';
import { connect } from 'react-redux';

class MyComponent extends React.Component {
  componentDidMount() {
    this.props.requestPageOfPlans();
  }
}

export default connect((state) => state, { requestPageOfPlans })(MyComponent);

所以这里的关键是连接设置。第一个参数是您希望如何将状态（您的 reducer）转换为 props 的数据。根据需要进行调整。第二个是您希望绑定的操作。您也可以手动导入调度，但我个人喜欢这种模式。它将动作设置为组件上的道具，您可以这样称呼它。只需根据需要将参数传递给它。这个页面在这里：https://github.com/reactjs/react-redux/blob/master/docs/api.md#connectmapstatetoprops-mapdispatchtoprops-mergeprops-options 更详细地解释了连接功能。

编辑

鉴于您在前端进行分页，您需要调整连接 mapStateToProps 函数以将分页数据向下传递给组件，然后循环通过它以显示您需要的内容。就我个人而言，我会在后端进行分页，并对每个页面进行新的请求。取决于您期望拥有多少条记录。

所以在连接中做这样的事情：

export default connect((state) => {
  return {
    startIndex: state.paging.lastIndex,
    pageSize: state.paging.pageSize,
    lastIndex: state.paging.lastIndex,
    plans: state.plans
  };
}, { requestPageOfPlans })(MyComponent);

然后在您的组件中，使用这些索引遍历计划：

 render() {
   const plans = [];
   const maxIndex = Math.min(this.props.startIndex + this.props.pageSize, this.props.lastIndex);
   for (let i = this.props.startIndex || 0; i < maxIndex; i++) {
     const plan = this.props.plans[i];
     plans.push(<Plan key={plan.id} plan={plan} />);
   }

   return (
     <ul>{plans}</ul>
   );
 }

再次假设您计划如何渲染它，如果您有一个名为 Plan 的组件等。但这大致就是您可以使用它的方式。

Answer 2

componentDidMount 是加载第一个页面的好时机。

顺便说一句，在我看来，页面更改不是动作，它只是加载数据的一些参数。

动作创作者

const userurl = '/rest/users'

export const loadUsers = (page = 0) => {
  return (dispatch) => {
    axios.get(userurl+"?page="+page)
    .then(function(resp) {
      dispatch(loadUsersOK(resp.data._embedded.users, resp.data.page));
    })
    .catch(function(error) {
     ...
    })
  };
}

组件 JSX

<span style={{marginRight:15, fontSize: 14, color: '#333'}}>{page.number*page.size+1}-{page.number*page.size+page.size} of {' '} {page.totalElements}</span>
<FlatButton style={flatButtonStyle} icon={<NavigationChevronLeft/>} onTouchTap={this.prevPage} />
<FlatButton style={flatButtonStyle} icon={<NavigationChevronRight/>} onTouchTap={this.nextPage} />

组件处理程序

 prevPage() {
    const { page } = this.props.users;
    this.props.loadUsers(page.number - 1);
  }

  nextPage() {
    const { page } = this.props.users;
    this.props.loadUsers(page.number + 1);
  }

连接

const mapStateToProps = state => {
  return {
    users: state.users
  }
}

const mapDispatchToProps = (dispatch, ownProps) => {
  return {
    loadUsers: (page=0) => dispatch(loadUsers(page))
  }
}

const Wrapped = connect(
  mapStateToProps,
  mapDispatchToProps
)(Users)

只有一个动作

export const loadUsersOK = (result, page) => ({
  type: LOAD_USERS_OK,
  result,
  page
})

希望对你有帮助。