React-Router：如何在路由转换之前等待异步动作

Question

是否可以thunk在特定路由上调用称为a的异步redux操作，并且在响应成功或失败之前不执行转换？

用例

我们需要从服务器加载数据并用初始值填写表单。从服务器获取数据之前，这些初始值不存在。

像这样的一些语法会很棒：

<Route path="/myForm" component={App} async={dispatch(loadInitialFormValues(formId))}>

Answer 1

要回答防止在响应成功或失败之前过渡到新路线的原始问题，请执行以下操作：

因为您使用的是redux thunk，所以操作创建者成功或失败可能会触发重定向。我不知道您的特定动作/动作创建者是什么样子，但是这样的方法可能有效：

import { browserHistory } from 'react-router'

export function loadInitialFormValues(formId) {
  return function(dispatch) {
    // hit the API with some function and return a promise:
    loadInitialValuesReturnPromise(formId)
      .then(response => {
        // If request is good update state with fetched data
        dispatch({ type: UPDATE_FORM_STATE, payload: response });

        // - redirect to the your form
        browserHistory.push('/myForm');
      })
      .catch(() => {
        // If request is bad...
        // do whatever you want here, or redirect
        browserHistory.push('/myForm')
      });
  }
}

跟进。 在组件上输入路径/在componentWillMount上并显示微调器时加载数据的常见模式：

来自关于异步操作的redux文档http://redux.js.org/docs/advanced/AsyncActions.html

• 通知减速器该请求开始的动作。
  
  

减速器可以通过在状态下切换isFetching标志来处理此操作。这样，UI知道了显示微调框的时候了。

• 通知减速器该请求成功完成的操作。
  
  

减速器可以通过将新数据合并到它们管理的状态并重置isFetching来处理此操作。UI将隐藏微调框，并显示获取的数据。

• 通知减速器该请求失败的操作。
  
  

减速器可以通过重置isFetching来处理此操作。另外，某些化简工具可能希望存储错误消息，以便UI可以显示它。

我按照您的情况作为粗略指导，遵循了以下一般模式。您不必使用诺言

// action creator:
export function fetchFormData(formId) {
  return dispatch => {
    // an action to signal the beginning of your request
    // this is what eventually triggers the displaying of the spinner
    dispatch({ type: FETCH_FORM_DATA_REQUEST })

    // (axios is just a promise based HTTP library)
    axios.get(`/formdata/${formId}`)
      .then(formData => {
        // on successful fetch, update your state with the new form data
        // you can also turn these into their own action creators and dispatch the invoked function instead
        dispatch({ type: actions.FETCH_FORM_DATA_SUCCESS, payload: formData })
      })
      .catch(error => {
        // on error, do whatever is best for your use case
        dispatch({ type: actions.FETCH_FORM_DATA_ERROR, payload: error })
      })
  }
}

// reducer

const INITIAL_STATE = {
  formData: {},
  error: {},
  fetching: false
}

export default function(state = INITIAL_STATE, action) {
  switch(action.type) {
    case FETCH_FORM_DATA_REQUEST:
      // when dispatch the 'request' action, toggle fetching to true
      return Object.assign({}, state, { fetching: true })
    case FETCH_FORM_DATA_SUCCESS:
      return Object.assign({}, state, {
        fetching: false,
        formData: action.payload
      })
    case FETCH_FORM_DATA_ERROR:
      return Object.assign({}, state, {
        fetching: false,
        error: action.payload
      })
  }
}

// route can look something like this to access the formId in the URL if you want
// I use this URL param in the component below but you can access this ID anyway you want:
<Route path="/myForm/:formId" component={SomeForm} />

// form component
class SomeForm extends Component {
  componentWillMount() {
    // get formId from route params
    const formId = this.props.params.formId
    this.props.fetchFormData(formId)
  }

  // in render just check if the fetching process is happening to know when to display the spinner
  // this could also be abstracted out into another method and run like so: {this.showFormOrSpinner.call(this)}
  render() {
    return (
      <div className="some-form">
        {this.props.fetching ? 
          <img src="./assets/spinner.gif" alt="loading spinner" /> :
          <FormComponent formData={this.props.formData} />
        }
      </div>
    )
  }
}

function mapStateToProps(state) {
  return {
    fetching: state.form.fetching,
    formData: state.form.formData,
    error: state.form.error
  }
}

export default connect(mapStateToProps, { fetchFormData })(SomeForm)