douyi2798 2018-11-02 14:08
浏览 245


How can I filter fields with the mongo-go-driver. Tried it with findopt.Projection but no success.

type fields struct {
    _id int16

s := bson.NewDocument()
filter := bson.NewDocument(bson.EC.ObjectID("_id", starterId))

var opts []findopt.One
opts = append(opts, findopt.Projection(fields{
    _id: 0,

staCon.collection.FindOne(nil, filter, opts...).Decode(s)

In the end, I want to suppress the field "_id". But the documents didn't change.

  • 写回答

1条回答 默认 最新

  • duanchou6534 2018-11-05 13:54

    The reason why it doesn't work for you is because the field fields._id is unexported, and as such, no other package can access it (only the declaring package).

    You must use a field name that is exported (starts with an uppercase latter), e.g. ID, and use struct tags to map it to the MongoDB _id field like this:

    type fields struct {
        ID int `bson:"_id"`

    And now to perform a query using a projection:

    projection := fields{
        ID: 0,
    result := staCon.collection.FindOne(
        nil, filter, options.FindOne().SetProjection(projection)).Decode(s)

    Note that you may also use a bson.Document as the projection, you don't need your own struct type. E.g. the following does the same:

    projection := bson.NewDocument(
        bson.EC.Int32("_id", 0),
    result := staCon.collection.FindOne(
        nil, filter, options.FindOne().SetProjection(projection)).Decode(s)
    本回答被题主选为最佳回答 , 对您是否有帮助呢?



    • ¥15 Qt 不小心删除了自带的类,该怎么办
    • ¥15 我需要在PC端 开两个抖店工作台客户端.(语言-java)
    • ¥15 有没有哪位厉害的人可以用C#可视化呀
    • ¥15 可以帮我看看代码哪里错了吗
    • ¥15 设计一个成绩管理系统
    • ¥15 PCL注册的选点等函数如何取消注册
    • ¥15 问一下各位,为什么我用蓝牙直接发送模拟输入的数据,接收端显示乱码呢,米思齐软件上usb串口显示正常的字符串呢?
    • ¥15 Python爬虫程序
    • ¥15 crypto 这种的应该怎么找flag?
    • ¥15 代码已写好,求帮我指出错误,有偿!