React Komposer，react and Meteor

Question

我正在使用react Komposer meteor和react。我有这个组件

import React from 'react';
import getMuiTheme from 'material-ui/styles/getMuiTheme';
import lightBaseTheme from 'material-ui/styles/baseThemes/lightBaseTheme';
import MuiThemeProvider from 'material-ui/styles/MuiThemeProvider';

const lightMuiTheme = getMuiTheme(lightBaseTheme);

const Questiondetails = ({ thequestion }) => (
  <div>
    <MuiThemeProvider muiTheme={lightMuiTheme}>
      <h4>{thequestion.header}</h4>
    </MuiThemeProvider>
  </div>
);


export default Questiondetails;

这是一个容器

import { Meteor } from 'meteor/meteor';
import React from 'react';
import { composeWithTracker } from 'react-komposer';
import CircularProgress from 'material-ui/CircularProgress';
import darkBaseTheme from 'material-ui/styles/baseThemes/darkBaseTheme';
import MuiThemeProvider from 'material-ui/styles/MuiThemeProvider';
import getMuiTheme from 'material-ui/styles/getMuiTheme';
import Questiondetails from '../../../ui/components/Questiondetails/Questiondetails.jsx';
import Questions from '../../Collections/Questions/Questions.js';

function composer(props, onData) {
  const handle = Meteor.subscribe('singleQuestion', props._id);

  if (handle.ready()) {
    const thequestion = Questions.findOne({ id: props._id });
    onData(null, { thequestion });
  }
}

const darkMuiTheme = getMuiTheme(darkBaseTheme);

const MyLoading = () => (<div style={{ width: '90%', position: 'relative'   }}>
  <MuiThemeProvider muiTheme={darkMuiTheme}>
    <div style={{ margin: 'auto', right: 0, left: 0, maxWidth: 200, position: 'relative' }}>
      <CircularProgress size={1.0} />
    </div>
  </MuiThemeProvider>
</div>);

export { MyLoading };

export default composeWithTracker(composer, MyLoading)(Questiondetails);

我在问Exception from Tracker recompute function: debug.js:41TypeError: Cannot read property 'header' of undefined我能做什么。当我看着流星玩具时。我可以在组件中看到订阅。

这是我的出版物

import { Meteor } from 'meteor/meteor';

// import the db
import Questions from '../../../../api/Collections/Questions/Questions.js';

// the publish
Meteor.publish('singleQuestion', function(id){
  return Questions.find({ _id: id });
});

Answer 1

很可能你没有得到数据记录。

即使在订阅handle准备就绪之后，查询也有可能返回undefined，因为集合中没有数据，或者查询是错误的。

在这种情况下，查询似乎确实是错误的，导致您将undefined传递给组件，而不是预期的对象。

如果您提供一个字符串作为find()或findOne()的第一个参数，则假定您指的是_id，因此它可以防止出现类似于您犯下的(常见)错误(Questions.findOne({ id: props._id })，使用id键而不是_id)。

您可以使用error参数，以便更容易地捕获此类情况(并在出现实际错误时显示有意义的错误消息)。

我还建议将thequestion更改为question或theQuestion (可读性更好)，除非有很好的理由不这样做。

function composer(props, onData) {
  const handle = Meteor.subscribe('singleQuestion', props._id);

  if (handle.ready()) {
    const question = Questions.findOne(props._id);
    let error = null;
    if (!question) {
      error = new Error('no question matches the provided id');
    }
    onData(error, {question});
  }
}