我試圖存儲SQL查詢的數據集在一個JSON結構和顯示。我已經差不多完成了。現在的問題是嵌套結構的結果集是空的,我不想顯示它。Golang:在嵌套結構存儲SQL結果集和省略,如果空
同樣的問題specified here但使用指針在恐慌掃描,因爲我使用&user.Profile.Firstname
2015/11/01 16:42:16 Panic recovery -> runtime error: invalid memory address or nil pointer dereference
可能是當如果我刪除的指針則一切正常只是空場仍然結束。我很困惑如何實現這一點。
package main
import (
"database/sql"
"github.com/gin-gonic/gin"
_ "github.com/go-sql-driver/mysql"
"log"
)
type User struct {
Id int64
Username string
Email string
Profile Profile `json:",omitempty"`
}
type Profile struct {
Id int64 `json:",omitempty"`
UserId int64 `json:",omitempty"`
Firstname *string `json:",omitempty"`
Lastname *string `json:",omitempty"`
}
var DB *sql.DB
func checkErr(err error, msg string) {
if err != nil {
log.Fatal(msg, err)
}
}
func main() {
DB, _ = sql.Open("mysql", "username:[email protected]/database")
defer DB.Close()
r := gin.Default()
v1 := r.Group("api/v1/")
{
v1.GET("users", GetUsers)
}
r.Run(":8080")
}
func GetUsers(c *gin.Context) {
stmt, err := DB.Query("Select users.id, username , email , firstname , lastname from users left join profiles on users.id = profiles.user_id ")
if err != nil {
panic(err.Error())
}
defer stmt.Close()
users := []User{}
for stmt.Next() {
var user User
err := stmt.Scan(&user.Id, &user.Username, &user.Email, &user.Profile.Firstname, &user.Profile.Lastname)
if err != nil {
panic(err.Error())
}
users = append(users, user)
}
c.JSON(200, &users)
}
輸出:
{
"Id": 1,
"Username": "test1",
"Email": "[email protected]",
"Profile": {
"Firstname": "John",
"Lastname": "Doe"
}
},
{
"Id": 2,
"Username": "test2",
"Email": "[email protected]",
"Profile": {
}
},