为结构测试/实体找到无效字段。用户实体的

Question

我是一个新手，我决定创建一个RestAPI来练习技能。现在我要在User之间建立一对多的关系书和实体。但是当我试图保存Book时实体到数据库，它显示我这样的错误:

invalid field found for struct test/entity.UserEntity's field Books: define a valid foreign key for relations or implement the Valuer
/Scanner interface

下面是我的代码:

UserEntity

type UserEntity struct {
gorm.Model
Username string       `gorm:"unique;not null"`
Email    string       `gorm:"unique;not null"`
Password string       `gorm:"not null"`
Books    []BookEntity `gorm:"constraint:OnUpdate:CASCADE,OnDelete:SET NULL;"`
}
func (*UserEntity) TableName() string {
return "users"
}

BookEntity

type BookEntity struct {
gorm.Model
Name     string `gorm:"not null"`
Isbn     int    `gorm:"unique;not null"`
AuthorID uint
}
func (*BookEntity) TableName() string {
return "books"
}

BookAddModel

type BookAddModel struct {
Name string `json:"name"`
Isbn int    `json:"isbn"`
}
func (bookModel *BookAddModel) ToModel(ctx *gin.Context) {
ctx.Bind(&bookModel)
}

下面是我向数据库中添加实体的代码

func AddBook(bookModel models.BookAddModel, author *entity.UserEntity) entity.BookEntity {
var book entity.BookEntity
mapstructure.Decode(bookModel, &book)
config.DbSession.Create(&book) // <<<< here's error
author.Books = append(author.Books, book)
config.DbSession.Save(author)
return book
}

配置

var DbSession *gorm.DB
var PostgresData = "host=localhost user=postgres password=4122 dbname=gorm port=5432 sslmode=disable TimeZone=Asia/Shanghai"

那么问题是什么呢?如果你知道，请告诉我。我真的很感激!

Answer 1

您应该为UserEntity.Books设置foreignKey:

type UserEntity struct {
...
Books    []BookEntity `gorm:"foreignKey:AuthorID,..."`
}

不要忘记先删除表，然后重新运行AutoMigrations:

db.AutoMigrate(&UserEntity{})
db.AutoMigrate(&BookEntity{})