如何在mongodb中的數組中查找元素？

Question

我試圖在數組中找到具有某個元素的對象：

所以我的查詢如下：

router.get('/', function(req, res) {
    var userSubscribed = req.user.email;
    db.posts.find({ "SubscriberList": { $elemMatch: userSubscribed}}, function(err, object){
        if (err) console.log(err);
        else console.log(object);
        res.render('index', { title: 'Home', user: req.user});
    })
});

正在控制台的錯誤如下：

{ [MongoError: Can't canonicalize query: BadValue $elemMatch needs an Object] name: 'MongoError'}

我的數據庫中一個對象的示例：

{ 
    "_id" : ObjectId("5490afa8416841105626cc41"), 
    "post" : { 
        "title" : "Ralph", 
        "category" : "Node", 
        "date" : "2014-12-11", 
        "description" : "Node coming soon!" 
    }, 
    "owner" : "bousamra.ralph@gmail.com", 
    "status" : "active", 
    "category" : "Node", 
    "SubscriberList" : ["alaric@hotmail.com" ]
}

Answer 1

通常，只在匹配單個數組元素的多個屬性時才需要使用$elemMatch 。

使用SubscriberList只是一個字符串數組，您可以簡單地執行以下操作：

router.get('/', function(req, res) {
    var userSubscribed = req.user.email;
    db.posts.find({ "SubscriberList": userSubscribed }, function(err, object){
        if (err) console.log(err);
        else console.log(object);
        res.render('index', { title: 'Home', user: req.user});
    })
});

Answer 2

您應該嘗試以下代碼：

router.get('/', function(req, res) {
var userSubscribed = req.user.email;
db.posts.find({owner:userSubscribed}, function(err, object){
    if (err) console.log(err);
    else console.log(object);
    res.render('index', { title: 'Home', user: req.user});
})
});