在MongoDB中存在数据的同时返回空数组的API

• Z时代
• 2024-01-10
• 分类：问答

全部。我是一名初学者，并试图用Express后端构建一个React应用程序。我已经构建了一个从MongoDB获取数据的API。这里是Robo3T所示的MongoDB内部的数据。我的问题是，数据包含选项数组，似乎在MongoDB中显示数据（使用Robo3T），但选项数组在API响应中为空。在MongoDB中存在数据的同时返回空数组的API

Data as shown by Robo3T

的API响应如下：

[ 
{ 
    _id: "5a21536a70ef53552d30e709", 
    q_text: " ¿Cuál es tu edad, sexo y lugar de nacimiento?", 
    options: [ ] 
}, 
{ 
    _id: "5a21536a70ef53552d30e70a", 
    q_text: "¿Actualmente asistes a la escuela?", 
    options: [ ] 
}, 
{ 
    _id: "5a21536a70ef53552d30e70b", 
    q_text: "¿Cuál es tu grado de estudios? (grado y programa)", 
    options: [ ] 
} 
] 

Server.js

//importing all dependencies 
var express = require('express'); 
var bodyParser = require('body-parser'); 
var mongoose = require('mongoose'); 
var Question = require('./models/Question'); 
//Connecting to MongoDB server 
mongoose.connect('mongodb://localhost/local', {useMongoClient: true}); 
var db = mongoose.connection; 
db.on('error', console.error.bind(console, 'MongoDB connection error')); 
//Creating our Express App Instance 
var app = express(); 
var router = express.Router(); 
//Specifying the port number 
var port = process.env.PORT || 3001; 
//Configuring body-parser 
app.use(bodyParser.json()); 
app.use(bodyParser.urlencoded({extended: true})); 
//To prevent errors from Cross Origin Resource Sharing, we will set our headers to allow CORS with middleware like so: 
app.use(function(req, res, next) { 
    res.setHeader('Access-Control-Allow-Origin', '*'); 
    res.setHeader('Access-Control-Allow-Credentials', 'true'); 
    res.setHeader('Access-Control-Allow-Methods', 'GET,HEAD,OPTIONS,POST,PUT,DELETE'); 
    res.setHeader('Access-Control-Allow-Headers', 'Access-Control-Allow-Headers, Origin,Accept, X-Requested-With, Content-Type, Access-Control-Request-Method, Access-Control-Request-Headers'); 
    //and remove cacheing so we get the most recent comments 
    res.setHeader('Cache-Control', 'no-cache'); 
    next(); 
}); 
router.get('/', function(req, res){ 
    res.json({message : 'API initialized'}); 
}) 
router.route('/questions') 
    //retrieve all questions from database 
    .get(function(req, res){ 
     Question.find({}, function(err, questions){ 
      if(err){ 
       res.status(500).send({error: 'Could not fetch Questions'}); 
      } else{ 
       res.json(questions); 
      } 
     }) 
    }) 
app.use('/api', router); 
//start the server and listen for requests 
app.listen(port, function(){ 
    console.log(`Server listening on port ${port}`); 
}) 

模型/ Question.js

var mongoose = require('mongoose'); 
var Schema = mongoose.Schema; 
var ObjectId = mongoose.Schema.Types.ObjectId; 
var question = new Schema({ 
    q_text:String, 
    options:[{ 
     type: String, 
     o_text: String 
    }] 
}); 
module.exports = mongoose.model('Question',question); 

从./components/App.jsx

import React, {Component} from 'react'; 
import axios from 'axios'; 
import Question from './Question'; 
class App extends Component{ 
    constructor(props){ 
     super(props); 
     this.state = { 
      dataLoaded: false, 
      questions: [] 
     }; 
     this.loadQuestions = this.loadQuestions.bind(this); 
    } 
    loadQuestions(){ 
     axios.get(this.props.url) 
      .then(res => { 
       this.setState({questions: res.data}); 
       this.setState({dataLoaded: true}) 
      }) 
    } 
    componentDidMount(){ 
     this.loadQuestions(); 
    } 
    render(){ 
     if(this.state.dataLoaded){ 
      console.log(this.state.questions[2].options); 
      return(
       <div> 
        <Question text={this.state.questions[1].q_text}/> 
       </div> 
      ) 
     } 
     else{ 
      return(
       <div>Loading...</div> 
      ); 
     } 
    } 
} 
export default App; 

回答：

以上是 在MongoDB中存在数据的同时返回空数组的API 的全部内容， 来源链接： utcz.com/qa/257640.html