Question

有人可以向我解释为什么，当我执行以下代码时，我会得到一个空列表？

Post.find({ "emailPublisher": req.body.emailUser }, { _id: 0, "idPost": 1 }, function (err, idsposts) {
    console.log(idsposts)
    for (i in idsposts) { list.push(idsposts[i].idPost) }
});
console.log("list is " + list);

看起来像这一行：

console.log("list is " + list);

在查找查询之前发生。

Answer 1

您需要将其插入回调中：

Post.find({ "emailPublisher": req.body.emailUser }, { _id: 0, "idPost": 1 }, function (err, idsposts) {
    console.log(idsposts)
    for (i in idsposts) { list.push(idsposts[i].idPost) }
    console.log("list is " + list);
});

find是一个异步操作。

Answer 2

那么为什么这个查询不起作用？

Like.aggregate({ $group: { _id: "$idPost", totalNumLikes: { $sum: 1 } } }, function (err, likesResult) {
    if (err) {
        console.log("error in app.post(numlikesforUser)")
        return res.send(err);
    }
    Post.find({idPost: {$in: likesResult.map(r => r._id)}, "emailPublisher": req.body.emailUser }, function (err, posts) {
    for (var i =0; i < likesResult.length; i++) {
         var result = likesResult[i]; 
         var post = posts.filter(p => p._id === result._id)[0];
         if (post != null) {
                likesCount = likesCount + result.totalNumLikes
            }
        }
    console.log("likescount is:::::::::::::" + likesCount);
   });
});

解释一个mongoose查询的输出

2 个答案: