我正在利用MongoDB和Mongoose构建汽车API。我想创建一个端点，该端点使我可以基于传递给req.query的搜索词来查询任何字段。我有两个要连接到我的汽车模型的模型（类别和制造商）。到目前为止，我可以利用Mongoose的填充方法获取所有结果。但是，当我尝试查询时，被引用的字段返回null。

此外，我不确定在填充两个字段（类别和品牌）时如何查询所有字段。

是否存在一种更好的方法来填充每个发现的类别和品牌？有没有更好的方法来搜索集合中的所有字段？

下面的示例代码：

-型号- 汽车

const carSchema = mongoose.Schema({
    make: {
        type: mongoose.Schema.Types.ObjectId,required: true,ref: 'Make'
    },model: {
        type: String,trim: true,required: true
    },description: {
        type: String,year: {
        type: Number,min: 1900,max: 2100
    },categories: [{ 
        type: {
            type: mongoose.Schema.Types.ObjectId,ref: 'Category'
        }
    }],...
    }]
},{
    timestamps: true
})

const Car = mongoose.model('Car',carSchema)

module.exports = Car

类别

const categorySchema = mongoose.Schema({
    type: {
        type: String,unique: true
    }
})

const Category = mongoose.model('Category',categorySchema)

module.exports = Category

制造

const makeSchema = mongoose.Schema({
    name: {
        type: String,unique: true
    }
})

const Make = mongoose.model('Make',makeSchema)

module.exports = Make

-汽车路线-

...

router.get('/cars/:id',async (req,res) => {
    const _id = req.params.id

    try {
        const car = await Car.findOne({ _id })

        if (!car) {
            return res.status(404).send()
        }

        res.status(200).send(car)
    } catch (e) {
        res.status(500).send(e)
    }
})

router.get('/cars',res,next) => {
    const match = {}
    const sort = {}

    if (req.query.make) {
        match.make = { "$regex": req.query.make,"$options": "i"}
    }

    try {
        console.log(match)
        const cars = await Car.find({})
            .populate({
                path: 'make',select: 'name',match
            })
            .populate({
                path: 'categories.type',model: 'Category',select: 'type _id'
            })

        res.send(cars)
    } catch(e) {
        console.log(e.message)
        res.status(500).send(e)
    }
})

...

module.exports = router

-输出- 通过查询时（/ cars？make = koenigsegg）

[
    {
        "_id": "RANDOMID","make": "null","model": "360 Modena","description": "Testing 66","year": 2015,"categories": [
            {
                "_id": "5dcdb6e8fa88224721a0711c","type": {
                    "_id": "IDOFHYPERCARINCATEGORYCOLLECTION","type": "Hyper"
                }
            },{
                "_id": "5dcdb6e8fa88224721a0711b","type": {
                    "_id": "IDOFSUPERCARINCATEGORYCOLLECTION","type": "Super"
                }
            }
        ],... OTHER FIELDS HERE ...
        "createdAt": "2019-11-14T20:19:52.248Z","updatedAt": "2019-11-14T20:19:52.248Z","__v": 0
    },.. OTHER RECORDS HERE ...
]

未通过查询时（/ cars）=

[
    {
        "_id": "RANDOMID","make": "IDOFFERRARIInmAKECOLLECTION",.. OTHER RECORDS HERE ...
]