在Go中设置导入结构的标签

Question

I'm using gorm (go orm) to retrieve data from my database that will be encoded in JSON. Gorm provides a default struct for primary keys and time tracking, whose DeletedAt attribute should not be encoded in JSON.

I've written a small example, that doesn't output the password but the DeletedAt attribute is still visible.

package main

import (
    "encoding/json"
    "fmt"
    "os"

    "github.com/jinzhu/gorm"
    _ "github.com/lib/pq"
    _ "github.com/mattn/go-sqlite3"
)

// Struct from the gorm package:
//
// type Model struct {
//     ID        uint `gorm:"primary_key"`
//     CreatedAt time.Time
//     UpdatedAt time.Time
//     DeletedAt *time.Time
// }

// Defines the database model for gorn
type User struct {
    gorm.Model
    Username string `json:"username" sql:"size:32; not null; unique"`
    Password string `json:"password" sql:"not null"`
    Locale   string `json:"locale"   sql:"not null"`
}

// Public JSON version of database model
type PublicUser struct {
    *User
    DeletedAt bool `json:"deletedAt,omitempty"`
    Password  bool `json:"password,omitempty"`
}

func main() {
    db, err := gorm.Open("sqlite3", "storage.db")

    if err != nil {
        fmt.Println(err)
    }

    u := &User{}
    db.Where("id = ?", 3).Find(&u)

    json.NewEncoder(os.Stdout).Encode(PublicUser{
        User: u,
    })
}

This is the ourput I get if I run my script:

{
    "ID":3,
    "CreatedAt":"2015-05-13T14:54:23.5577227Z",
    "UpdatedAt":"2015-05-13T14:54:23.5577227Z",
    "DeletedAt":null,
    "username":"dan",
    "locale":"en_US"
}

I modified the example of Alfred Rossi to imitate the behavior and I got the same result.

Answer 1

You can just shadow the field with a bool set to false and tag it with omitempty

For example

type User struct {
    Username  string `json:"username"`
    DeletedAt int    `json:"deleted_at"`
}

type PublicUser struct {
    *User
    DeletedAt bool `json:"deleted_at,omitempty"`
}

Feel free to play with it here. Also see this blog post of Attila Oláh.