聚合返回空数组-猫鼬 [英] aggregate returns empty array - mongoose

问题描述

我有以下两个简单查询:

I have the following two simple queries:

Comment.aggregate([{$match: { _id: req.params.id }}])
  .exec(function(err, result) {
    // result is empty
  });

Comment.find({ _id: req.params.id })
  .exec(function (err, result) {
    // correct result returned
  });

我的问题是，聚合函数返回一个空数组.他们不应该返回相同的结果吗?

My problem is, that the aggregate-Function returns an empty array. Aren't they supposed to return the same result?

推荐答案

是的，但是您需要将id(它是一个字符串)强制转换为objectID:)

Yes, but you need to cast the id (which is a string) to an objectID :)

let idToSearch = mongoose.Types.ObjectId(req.params.id)
Comment.aggregate([{$match: { _id: idToSearch }}])
.exec(function(err, result) {
    // result is now correct :)
});

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