Mongoose .populate() 在Node.js应用中无法生效问题求助

各位好，这是我首次发帖！我遇到了Mongoose的populate方法完全不起作用的问题，以下是相关代码：

模型定义 #

Space模型 #

const spaceSchema = Schema(
    {
        user: {
            type: Schema.Types.ObjectId,
            required: true,
            ref: "User",
        },
        name: {
            type: String,
            required: true,
        },
        days: [{ type: Schema.Types.ObjectId, refPath: "Day" }],
    },
    {
        versionKey: false,
            timestamps: true 
        },
);

const Space = mongoose.model("Space", spaceSchema);

module.exports = Space;

Day模型 #

const daySchema = Schema(
    {
        space: { type: Schema.Types.ObjectId, refPath: "Space" },
        date: {
            type: String,
            required: true,
        },
        water: {
            type: Boolean,
        },
        fertilizer: {
            type: Boolean,
        },
        transplant: {
            type: Boolean,
        },
        comment: {
            type: String,
        },
    },
    {
        versionKey: false,
            timestamps: true 
        },
);

const Day = mongoose.model("Day", daySchema);

module.exports = Day;

控制器代码（/api/spaces/:id路由） #

const getSpace = asyncHandler(async (req, res) => {
    const space = await Space.findById(req.params.id).populate("days");
    res.status(200).json(space);
});

当前返回结果 #

{
    "_id": "63580115978dbf8f2f5a7a50",
    "user": "63501ab84613855834daa4ef",
    "name": "spaceName",
    "days": []
}

我尝试了多种方法，但结果始终如此。期望返回的结果应包含days数组的具体文档数据，示例如下：

{
    "space": {
        "_id": "63580115978dbf8f2f5a7a50",
        "user": "63501ab84613855834daa4ef",
        "name": "spaceName",
        "days": [
            {
                "_id": "63581af565aed8cad3210046",
                "space": "63580115978dbf8f2f5a7a50",
                "date": "29/10/2022",
                "water": true,
                "fertilizer": true,
                "transplant": false,
                "comment": "This is a comment.",
                "createdAt": "...",
                "updatedAt": "..."
            },
            {
                "_id": "63581af565aed8cad3210046",
                "space": "63580115978dbf8f2f5a7a50",
                "date": "29/10/2022",
                "water": false,
                "fertilizer": false,
                "transplant": true,
                "comment": "This is a comment.",
                "createdAt": "...",
                "updatedAt": "..."
            }
        ]
    }
}

若需要其他代码片段，请告知，感谢大家的帮助！

解决方案 #

问题出在refPath的错误使用上：refPath是用于动态关联不同模型的场景，而你这里是固定关联Day和Space模型，应该直接使用ref字段。

1. 修改模型定义 #

• Space模型：将days字段的refPath改为ref

days: [{ type: Schema.Types.ObjectId, ref: "Day" }],

• Day模型：将space字段的refPath改为ref

space: { type: Schema.Types.ObjectId, ref: "Space" },

2. 额外验证 #

• 确认Day集合中存在关联的文档，且其space字段值与目标Space的_id完全匹配
• 确认创建Space时，已将对应的Day文档_id正确添加到days数组中

修改后重新调用接口，populate("days")就能正常填充数组内容了。

内容的提问来源于stack exchange，提问作者JOlle11