node.js - 如何用nodejs和mongoose查找文档，为什么没有结果？

Question

person 集合中有 3 个文档，但我找不到()

mongodb 外壳:

> use test;
switched to db test
> db.person.find();
{ "_id" : ObjectId("527f18f7d0ec1e35065763e4"), "name" : "aaa", "sex" : "man", "height" : 180 }
{ "_id" : ObjectId("527f1903d0ec1e35065763e5"), "name" : "bbb", "sex" : "man", "height" : 160 }
{ "_id" : ObjectId("527f190bd0ec1e35065763e6"), "name" : "ccc", "sex" : "woman", "height" : 160 }

我的 nodejs 代码:

var mongoose = require('mongoose');
var db = mongoose.createConnection('mongodb://uuu:ppp@localhost:27017/test');
//mongoose.set('debug', true);

db.on('error', console.error.bind(console, 'connection error:'));
db.once('open', function callback () {
    console.log("connection success!");
    mongoose.model('person', mongoose.Schema({ name: String}),'person');

    var out = db.model('person');
    //console.log(out);
    out.find({},function(err, obj) {
        console.log(obj);
        console.log(1);
    });
});

但是，结果是: 连接成功! [] 1

Answer 1

问题是当你使用createConnection时，你需要使用创建连接的.model方法，而不是mongoose.model:

var db = mongoose.createConnection(...);

// wrong:
mongoose.model('person', mongoose.Schema({ name: String}),'person');

// right:
db.model('person', mongoose.Schema({ name: String}),'person');

// perform query:
db.model('person').find(...);

原因是，据我了解，模型与连接“相关联”。当您使用 mongoose.model 时，该模型与默认连接相关联，但您没有使用它(您使用的连接是通过 createConnection 显式创建的).

显示这一点的另一种方法是使用 modelNames:

// wrong:
mongoose.model('person', mongoose.Schema({ name: String}),'person');
console.log('default conn models:', mongoose.modelNames()); // -> [ 'person' ]
console.log('custom  conn models:', db.modelNames());       // -> []

// right:
db.model('person', mongoose.Schema({ name: String}),'person');
console.log('default conn models:', mongoose.modelNames()); // -> []
console.log('custom  conn models:', db.modelNames());       // -> [ 'person' ]