Question

具有以下Group Schema，

group.model.js

const Role = new mongoose.Schema({
  name: { type: String, required: true }, // ensure uniqueness withn group instance using addToSet
  description: { type: String, required: false }
});

const GroupSchema = new mongoose.Schema({
  name: { type: String, index: { unique: true, required: true, dropDups: true } },
  description: { type: String, required: false },
  roles: [Role],
  createdAt: {
    type: Date,
    default: Date.now
  }
});

我试图列出所有角色（子文档）得到一个特定的组

group.controller.js

function listRoles(req, res) {
  const group = req.group;
  console.log('GROUP: %j', group);
  const limit = parseInt(req.query.limit, 10) || 50;
  const skip = parseInt(req.query.skip, 10) || 0;

  Group.aggregate([
    { $match: { _id: req.params.groupId } },
    { $unwind: '$roles' },
    { $skip: skip },
    { $limit: limit }
  ], (err, result) => {
    if (err) {
      res.status(500);
      res.json({ message: 'Error. Cannot list roles', errror: err });
    }
    res.status(200);
    console.log('RESULT: %j', result);
    res.json(result);
  });
}

我应该得到一个有一个角色的数组，但是我得到一个空数组我的聚合代码出了什么问题？感谢您的反馈

注意：我试图只与管道中的$ match聚合，我也得到一个空数组...所以我猜。问题来自req.params.groupId应该是一个ObjectId ..我怎么能把它投出来？

的console.log

GROUP: {"_id":"5923e2e83afd4149bdf16c61","name":"Admin","description":"Administration group","__v":1,"createdAt":"2017-05-23T07:21:12.470Z","roles":[{"name":"Role1","description":"description role1","_id":"5923e2e83afd4149bdf16c62"}]}

RESULT: []

Answer 1

为了更好地诊断这一点，我建议从聚合管道中删除步骤并查看结果。但是，我怀疑您的问题是因为您在第一阶段没有匹配，因为您正在将字符串与ObjectId进行比较。试试这个：

const mongoose = require('mongoose')

// and in the aggregation:

{ $match: { _id: mongoose.Types.ObjectId(req.params.groupId) } }

node mongoose：聚合不给出预期结果

1 个答案: