User我正在嘗試在s 和s之間建立關聯PredictionsBag。我的問題是，如果我使用 GORM 的假定名稱來引用對象，一切都會正常，但我想稍微更改一下名稱。type User struct { gorm.Model // We’ll try not using usernames for now Email string `gorm:"not null;unique_index"` Password string `gorm:"-"` PasswordHash string `gorm:"not null"` Remember string `gorm:"-"` // A user’s remember token. RememberHash string `gorm:"not null;unique_index"` Bags []PredictionsBag}當然，每個用戶都擁有零個或多個PredictionsBags：type PredictionsBag struct { gorm.Model UserID uint // I want this to be "OwnerID" Title string NotesPublic string `gorm:"not null"` // Markdown field. May be published. NotesPrivate string `gorm:"not null"` // Markdown field. Only for (private) viewing and export. Predictions []Prediction}我想以.Related()通常的方式工作：func (ug *userGorm) ByEmail(email string) (*User, error) { var ret User matchingEmail := ug.db.Where("email = ?", email) err := first(matchingEmail, &ret) if err != nil { return nil, err } var bags []PredictionsBag if err := ug.db.Model(&ret).Related(&bags).Error; err != nil { return nil, err } ret.Bags = bags return &ret, nil}我的問題是，我無法找到一種方法來更改PredictionsBag.UserID為其他任何內容，并且仍然讓 GORM 弄清楚所涉及的關系。我一直在閱讀http://gorm.io/docs/has_many.html#Foreign-Key如果我將相關行更改為type User struct { // … Bags []PredictionsBag `gorm:"foreignkey:OwnerID"`}和type PredictionsBag struct { // … OwnerID uint // …}我收到此錯誤：[2019-07-28 14:23:49] invalid association [] 我究竟做錯了什么？我也一直在閱讀http://gorm.io/docs/belongs_to.html，但我不確定應該更密切地關注哪個頁面。
1 回答
largeQ
TA貢獻2039條經驗 獲得超8個贊
我回家后必須檢查一下Related()，但我認為您正在尋找的是Preload()這是我的示例，可以滿足您的需求。
package main
import (
"errors"
"fmt"
_ "github.com/go-sql-driver/mysql"
"github.com/jinzhu/gorm"
_ "github.com/jinzhu/gorm/dialects/mysql"
"log"
)
var DB *gorm.DB
func init() {
var err error
DB, err = gorm.Open("mysql", fmt.Sprintf("%s:%s@tcp(%s:3306)/%s?&parseTime=True&loc=Local", "root", "root", "localhost", "testing"))
if err != nil {
log.Fatal(err)
}
DB.DropTableIfExists(&User{}, &PredictionsBag{})
DB.AutoMigrate(&User{}, &PredictionsBag{})
user := User{Email:"[email protected]"}
user.Bags = append(user.Bags, PredictionsBag{OwnerID: user.ID, NotesPrivate: "1", NotesPublic: "1"})
DB.Create(&user)
}
func main() {
user := User{Email:"[email protected]"}
err := user.ByEmail()
if err != nil {
log.Println(err)
}
fmt.Println(user.ID, user.Email, "Bags:", len(user.Bags))
DB.Close()
}
type User struct {
gorm.Model
// We’ll try not using usernames for now
Email string `gorm:"not null;unique_index"`
Password string `gorm:"-"`
PasswordHash string `gorm:"not null"`
Remember string `gorm:"-"` // A user’s remember token.
RememberHash string `gorm:"not null;unique_index"`
Bags []PredictionsBag `gorm:"foreignkey:OwnerID"`
}
type PredictionsBag struct {
gorm.Model
OwnerID uint
Title string
NotesPublic string `gorm:"not null"` // Markdown field. May be published.
NotesPrivate string `gorm:"not null"` // Markdown field. Only for (private) viewing and export.
}
func (ug *User) ByEmail() error {
DB.Where("email = ?", ug.Email).Preload("Bags").Limit(1).Find(&ug)
if ug.ID == 0 {
return errors.New("no user found")
}
return nil
}
使用它可能適用于相關的，但我不確定還需要更改什么：
Bags []PredictionsBag `gorm:"foreignkey:OwnerID;association_foreignkey:ID"`
更新：
Related()如果你像下面這樣聲明外鍵，我就可以讓該方法起作用：
DB.Where("email = ?", ug.Email).Limit(1).Find(&ug)
if ug.ID == 0 {
return errors.New("no user found")
}
if err := DB.Model(&ug).Related(&ug.Bags, "owner_id").Error; err != nil {
return err
}
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