aggregate array of two collections mongodb

Question

I have two collections: Clinicas and Medicos . Clinicas can have a lot of Medicos . The relation was made this way:

medico: [{
    medicoId: {
      type: mongoose.Schema.Types.ObjectId,
      ref: 'medicos'
    }
  }],

And I will have the following json structure:

[
    {
        "nome": "clinica teste",
        "medico": [
            {
                "_id": "5e011a3796a5f80e3c0c8d20",
                "medicoId": {
                    "_id": "5dc5eef455a8f61698a0f2cd",
                    "nome": "Hancho Crutis",
                }
            },
            {
                "_id": "5e011a3796a5f80e3c0c8d1f",
                "medicoId": {
                    "_id": "5df16e5746783116709f09b7",
                    "nome": "camilinha",
                }
            }
        ],
    }
]

What I want is to make a "join" of these data. After a long research, I got this code but the response is always empty. Can someone tell me what am I doing wrong?

Clinicas.aggregate([
        { $unwind: "$medico"},   

        { $lookup: {
            from: "medicos",
            localField: "medicoId._id",
            foreignField: "_id",
            as: 'nome'
        }},

        { $match: {"medicoId._id": "5df16e5746783116709f09b7"}},       

    ])

Answer 1

You need to convert in ObjectId,

var mongoose = require('mongoose');

Clinicas.aggregate([
    { $unwind: "$medico" },

    {
        $lookup: {
            from: "medicos",
            localField: "medicoId._id",
            foreignField: "_id",
            as: 'nome'
        }
    },

    { $match: { "medicoId._id": mongoose.Types.ObjectId('5df16e5746783116709f09b7') } },

])