从聚合迭代Mongodb游标 [英] Iterate over Mongodb cursor from aggregate

问题描述

这是来自我的node.js后端的代码:

Here is code from my node.js backend:

app.get('/getpossibleconnections', auth, function(req, res){
    if (req.authenticated == false){
        res.send("Your session has expired.");
    } else {
        User.aggregate([
            { $match: { _id: { $nin: req.decoded.username.connections } } },
            { $sample: { size: 10 } },
        ]).next(function(err, docs) {
            console.log("horray");
        });
    }
});

我已尝试按照以下建议用toArray()和each()替换next():

I've tried replacing next() with toArray() and each() as suggested here:

http://mongodb.github.io/node-mongodb -native/2.0/tutorials/aggregation/

但是，我每次都会收到相同的错误:

However, I receive the same error every time:

TypeError: User.aggregate(...).next is not a function

为什么不能使用任何函数迭代返回的文档?

Why can't I iterate over the returned documents with any sort of function?

是不是因为User不是集合?

推荐答案

尝试一下:

var cursor = User.aggregate([
    { $match: { _id: { $nin: req.decoded.username.connections } } },
    { $sample: { size: 10 } },
]).cursor().exec();

cursor.each(function(err, doc) {
    //do something with doc
});

Mongoose处理聚合到游标对象的方式与您在链接中发布的Mongodb-native不同.此处的更多信息:猫鼬聚合光标文档

Mongoose handles an aggregate to cursor object differently than Mongodb-native as you posted in your link. More information here: mongoose aggregate cursor documentation

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