Express /猫鼬-无法显示数据

Question

我想用Mongoose与MongoDB挂钩，在Express中定义和使用API​​。到目前为止，我将对象保存为前端的精细形式输入。但是，当检索和显示我保存的数据时，我似乎迷失了。

以下是一些代码：

db.js：

const mongoose = require('mongoose');

//mongoose setup
mongoose.connect(mongooseUrl, { useNewUrlParser: true });
var db = mongoose.connection;
db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function() {
  console.log('mongoose connected to ' + mongooseUrl);
});

module.exports = db;

app.js：

var createError = require('http-errors');
var express = require('express');
var path = require('path');
var cookieParser = require('cookie-parser');
var logger = require('morgan');

// import routers
var indexRouter = require('./routes/index');
var usersRouter = require('./routes/users');
var apiRouter = require('./routes/api');


var app = express();

// view engine setup
app.set('views', path.join(__dirname, 'views'));
app.set('view engine', 'hbs');

app.use(logger('dev'));
app.use(express.json());
app.use(express.urlencoded({ extended: false }));
app.use(cookieParser());
app.use(express.static(path.join(__dirname, 'public')));

app.use('/', indexRouter);
app.use('/users', usersRouter);
app.use('/api', apiRouter);

// catch 404 and forward to error handler
app.use(function(req, res, next) {
  next(createError(404));
});

// error handler
app.use(function(err, req, res, next) {
  // set locals, only providing error in development
  res.locals.message = err.message;
  res.locals.error = req.app.get('env') === 'development' ? err : {};

  // render the error page
  res.status(err.status || 500);
  res.render('error');
});

module.exports = app;

/routes/api.js：

var express = require('express');
var mongoose = require('mongoose');
var db = require('../config/db.js');
var Kitten = require('../models/kitten.js');

var router = express.Router();

/* GET home page. */
router.get('/', function(req, res, next) {
  res.render('api', { 
    title: 'Test API',
    content: 'you\'re in the right place',
    buttontext: 'send POST request'
  });
});

router.post('/newKitten', function(req, res, next) {
    var kitty = new Kitten({
        name: req.body.name,
        color: req.body.color
    });
    console.log("new kitty: " + kitty.name + " color: " + kitty.color );
    kitty.save().then(console.log(kitty + " was saved to the database"));
    res.send('new: ' + kitty);

});

router.get('/kittens', function (req, res, next)  {
    var kittens = Kitten.find({}, 'name color');
    res.render('kittens', {title: 'Kittens', list_kittens: kittens });
});

module.exports = router;

models / kitten.js

const mongoose = require('mongoose');

var Schema = mongoose.Schema;

var kittenSchema = new Schema({
    name: String,
    color: String
});

var Kitten = mongoose.model("Kitten", kittenSchema);


module.exports = Kitten;

views / kitten.hbs：

<h1>{{title}}</h1>

<ul>
    {{#each list_kittens as |kitten|}}
        <li>name: {{kitten.name}}, color: {{kitten.color}}</li>
    {{/each}}
</ul>

现在一切都摆好了，当我访问http://localhost:3000/api/kittens时，我看到的是：

小猫被存放在MongoDB中，证明：

我不知道为什么它不呈现我保存在MongoDB数据库中的小猫……数据在那里，但是我似乎对猫鼬应该如何查询数据感到困惑。任何和所有帮助表示赞赏。我已经坚持了几天。

Answer 1

Model.find返回一个承诺。您必须添加函数then才能获得小猫并渲染它们：

Kitten.find(...)
  .then(kittens => {
    res.render(...)
  })

编辑

基于@Francisco Mateo注释，Kitten.find返回一个Query，您可以使用exec执行该操作。这是代码：

Kitten.find(...).exec()
  .then(kittens => {
    res.render(...)
  })

Answer 2

在routes / api.js中

var express = require('express');
var mongoose = require('mongoose');
var db = require('../config/db.js');
var Kitten = require('../models/kitten.js');

var router = express.Router();

/* GET home page. */
router.get('/', function(req, res, next) {
  res.render('api', { 
    title: 'Test API',
    content: 'you\'re in the right place',
    buttontext: 'send POST request'
  });
});

router.post('/newKitten', function(req, res, next) {
    var kitty = new Kitten({
        name: req.body.name,
        color: req.body.color
    });
    console.log("new kitty: " + kitty.name + " color: " + kitty.color );
    kitty.save().then(console.log(kitty + " was saved to the database"));
    res.send('new: ' + kitty);

});

router.get('/kittens', async function (req, res, next)  {  **//Change here**
    var kittens = await Kitten.find({}, 'name color');     **//change here** 
    res.render('kittens', {title: 'Kittens', list_kittens: kittens });
});

module.exports = router;

Kitten.find({}, 'name color')返回一个promise，因此您必须等待直到数据返回。