英文:
Golang mgo getting empty objects
问题
我正在尝试学习Go API开发。我在Docker容器中运行了一个MongoDB实例。我尝试按照一些指南进行操作，但在简单查询上失败了。我不完全理解这里的BSON和JSON标签的用法。我知道这些术语的含义。下面是我的代码。
import ("fmt""time""gopkg.in/mgo.v2/bson")const (hosts = "localhost:27017"database = "my_database"username = "dev1"password = "password123"collection = "users")type users struct {user string `bson:"user" json:"user"`data string}func main() {fmt.Println("Starting Application!")info := &mgo.DialInfo{Addrs: []string{hosts},Timeout: 60 * time.Second,Database: database,Username: username,Password: password,}session, err1 := mgo.DialWithInfo(info)if err1 != nil {panic(err1)}defer session.Close()col := session.DB(database).C(collection)var user usersvar books []usersvar username = "cat"col.Insert(&users{user: "dog", data: "blah"})err3 := col.Find(bson.M{"user": username}).One(&user)fmt.Println(user)fmt.Println(err3)count, err2 := col.Count()if err2 != nil {panic(err2)}fmt.Println(fmt.Sprintf("Messages count: %d", count))fmt.Println(user)col.Find(bson.M{}).All(&books)fmt.Println(books)}
基本上，我在打印行上得到了空对象，但是得到了正确的消息计数。如果有帮助，我是用robomongo插入的对象。
英文:
I'm trying to learn Go API development. I have a MongoDB instance running in a Docker container. I'm trying to follow a few guides but am failing on simple queries. I don't fully understand the use of BSON and JSON tags here. I do know what those terms mean. So here is my code.
import ("fmt""time""gopkg.in/mgo.v2/bson")const (hosts = "localhost:27017"database = "my_database"username = "dev1"password = "password123"collection = "users")type users struct {user string `bson:"user" json:"user"`data string}func main() {fmt.Println("Starting Application!")info := &mgo.DialInfo{Addrs: []string{hosts},Timeout: 60 * time.Second,Database: database,Username: username,Password: password,}session, err1 := mgo.DialWithInfo(info)if err1 != nil {panic(err1)}defer session.Close()col := session.DB(database).C(collection)var user usersvar books []usersvar username = "cat"col.Insert(&users{user: "dog", data: "blah"})err3 := col.Find(bson.M{"user": username}).One(&user)fmt.Println(user)fmt.Println(err3)count, err2 := col.Count()if err2 != nil {panic(err2)}fmt.Println(fmt.Sprintf("Messages count: %d", count))fmt.Println(user)col.Find(bson.M{}).All(&books)fmt.Println(books)}
Basically I'm getting empty objects on the print line but am getting the correct Message count. I inserted the objects with robomongo if that helps.
答案1
得分: 9
你必须导出结构体的字段，否则它们将被mgo包忽略。将users的字段更改为User和Data。
type users struct {User string `bson:"user" json:"user"`Data string `bson:"data" json:"data"`}
默认情况下，当从MongoDB转换/存储/检索结构体值时，使用字段名。如果你想使用不同的名称，可以使用标签来指定字段应该映射到哪些名称。
英文:
You must export fields of structs, else they are ignored by the mgo package. Change fields of users to User and Data.
type users struct {User string `bson:"user" json:"user"`Data string `bson:"data" json:"data"`}
By default when a struct value is transformed / stored / retrieved from MongoDB, the field name is used. If you want to use different names, you may use tags to tell what names should the fields map to.
通过集体智慧和协作来改善编程学习和解决问题的方式。致力于成为全球开发者共同参与的知识库，让每个人都能够通过互相帮助和分享经验来进步。
评论