mongodb - 通过id从集合中检索文档

Question

我收藏的元素:

type Room struct {
    Id bson.ObjectId            `json:"Id"                  bson:"_id"`
    Name string                 `json:"Name"                bson:"name"`
}

插入集合:

room = &Room{Id: bson.NewObjectId(), Name: "test"}
RoomCollection.Insert(room)

从集合中检索(任何):

roomX := &Room{}
if err := RoomCollection.Find(bson.M{}).One(roomX); err != nil {
    panic(err)
}
fmt.Printf("RoomX %s:\n%+v\n\n", roomX.Id, roomX)

输出:

RoomX ObjectIdHex("52024f457a7ea6334d000001"):
&{Id:ObjectIdHex("52024f457a7ea6334d000001") Name:test}

从集合中检索(通过 ID):

roomZ := &Room{}
if err := RoomCollection.Find(bson.M{"_id": room.Id}).One(roomZ); err != nil {
    panic(err) // throws "not found"
}

这会抛出“未找到”，我不明白为什么。

Answer 1

根据 reflect 包，字段的不同键值标记应以空格分隔。

By convention, tag strings are a concatenation of optionally space-separated key:"value" pairs. Each key is a non-empty string consisting of non-control characters other than space (U+0020 ' '), quote (U+0022 '"'), and colon (U+003A ':'). Each value is quoted using U+0022 '"' characters and Go string literal syntax.

mgo包无法读取标签，并将 Id 值存储为 id 而不是 _id。