Question

5.1 使用 redux

// action.js

export const REQUEST_TODO = 'REQUEST_TODO';
export const RESPONSE_TODO = 'RESPONSE_TODO';

const request = count => ({type: REQUEST_TODO, payload: {loading: true, count}});

const response = count => ({type: RESPONSE_TODO, payload: {loading: false, count}});

export const fetch = count => {
  return (dispatch) => {
    dispatch(request(count));

    return new Promise(resolve => {
      setTimeout(() => {
        resolve(count + 1);
      }, 1000)
    }).then(data => {
      dispatch(response(data))
    })
  }
}

//reducer.js
import { REQUEST_TODO, RESPONSE_TODO } from './actions';

export default (state = {
  loading: false,
  count: 0
}, action) => {
  switch (action.type) {
    case REQUEST_TODO:
      return {...state, ...action.payload};
    case RESPONSE_TODO:
      return {...state, ...action.payload};
    default:
      return state;
  }
}

// app.js
import React from 'react';
import { bindActionCreators } from 'redux';
import { connect } from 'react-redux';

import * as actions from './actions';

const App = ({fetch, count, loading}) => {
  return (
    <div>
      {loading ? <div>loading...</div> : <div>{count}</div>}
      <button onClick={() => fetch(count)}>add</button>
    </div>
  )
}

function mapStateToProps(state) {
  return state;
}

function mapDispatchToProps(dispatch) {
  return bindActionCreators(actions, dispatch)
}

export default connect(mapStateToProps, mapDispatchToProps)(App)

//index.js
import { render } from 'react-dom';
import { createStore, applyMiddleware } from 'redux';
import { Provider } from 'react-redux'
import thunkMiddleware from 'redux-thunk';

import reducer from './app/reducer';
import App from './app/app';

const store = createStore(reducer, applyMiddleware(thunkMiddleware));

render(
  <Provider store={store}>
    <App/>
  </Provider>
  ,
  document.getElementById('app')
)

5.2 使用 dva

// model.js
export default {
  namespace: 'demo',
  state: {
    loading: false,
    count: 0
  },
  reducers: {
    request(state, payload) {
      return {...state, ...payload};
    },
    response(state, payload) {
      return {...state, ...payload};
    }
  },
  effects: {
    *'fetch'(action, {put, call}) {
      yield put({type: 'request', loading: true});

      let count = yield call((count) => {
        return new Promise(resolve => {
          setTimeout(() => {
            resolve(count + 1);
          }, 1000);
        });
      }, action.count);

      yield put({
        type: 'response',
        loading: false,
        count
      });
    }
  }
}

//app.js

import React from 'react'
import { connect } from 'dva';

const App = ({fetch, count, loading}) => {
  return (
    <div>
      {loading ? <div>loading...</div> : <div>{count}</div>}
      <button onClick={() => fetch(count)}>add</button>
    </div>
  )
}

function mapStateToProps(state) {
  return state.demo;
}

function mapDispatchToProps(dispatch) {
  return {
    fetch(count){
      dispatch({type: 'demo/fetch', count});
    }
  }
}

export default connect(mapStateToProps, mapDispatchToProps)(App)

// index.js
import dva from 'dva';
import model from './model';
import App from './app';

const app = dva();

app.use({});

app.model(model);

app.router(() => <App />);

app.start();

• 使用 redux 需要拆分出 action 模块和 reducer 模块
• dva 将 action 和 reducer 封装到 model 中，异步流程采用 Generator 处理