英文:
panic: reflect: call of reflect.Value.Interface on zero Value on GORM .Create()
问题
我是你的中文翻译助手,以下是你要翻译的内容:
我刚开始学习Go和后端开发,我正在尝试在表之间建立多对多的关系。我使用了这个仓库来创建模型:https://github.com/harranali/gorm-relationships-examples/tree/main/many-to-many
我使用的是GORM和PostgreSQL。
我的模型如下:
type Book struct {
gorm.Model
Title string `json:"title"`
Author string `json:"author"`
Description string `json:"description"`
Category string `json:"category"`
Publisher string `json:"publisher"`
AuthorsCard []*AuthorsCard `gorm:"many2many:book_authorscard;" json:"authorscard"`
}
type AuthorsCard struct {
gorm.Model
Name string `json:"name"`
Age int `json:"age"`
YearOfBirth int `json:"year"`
Biography string `json:"biography"`
}
在连接到数据库并进行自动迁移后:
func init() {
config.Connect()
db = config.GetDB()
db.AutoMigrate(&models.Book{}, &models.AuthorsCard{})
}
我创建了一个函数来查看这个关系是如何工作的:
func TestCreate() {
var AuthorsCard = []models.AuthorsCard{
{
Age: 23,
Name: "test",
YearOfBirth: 1999,
Biography: "23fdgsdddTEST",
},
}
db.Create(&AuthorsCard)
var testbook = models.Book{
Title: "Test",
Author: "tst",
Description: "something",
}
db.Create(&testbook)
db.Model(&testbook).Association("AuthorsCard").Append(&AuthorsCard)
}
但是出现了以下错误:
panic: reflect: call of reflect.Value.Interface on zero Value [recovered]
panic: reflect: call of reflect.Value.Interface on zero Value
我该如何处理这个"Null"问题并建立正确的关系?
**更新:**问题的第一部分与GORM的版本有关。在将旧版本(github.com/jinzhu/gorm v1.9.16)更改为新版本(gorm.io/gorm v1.23.6)后,reflect错误的问题消失了。但是现在,当我想创建新的书籍时,出现了以下错误:
/go/pkg/mod/gorm.io/driver/postgres@v1.3.7/migrator.go:119 ERROR: there is no unique constraint matching given keys for referenced table "authors_cards" (SQLSTATE 42830)
[28.440ms] [rows:0] CREATE TABLE "book_authorscard" ("book_id" bigint,"authors_card_id" bigint,PRIMARY KEY ("book_id","authors_card_id"),CONSTRAINT "fk_book_authorscard_authors_card" FOREIGN KEY ("authors_card_id") REFERENCES "authors_cards"("id"),CONSTRAINT "fk_book_authorscard_book" FOREIGN KEY ("book_id") REFERENCES "books"("id"))
[GIN-debug] [WARNING] Creating an Engine instance with the Logger and Recovery middleware already attached.
**更新2:**我决定使用Migrator().DropTable()来删除表,这样做有点奏效,所有的错误都消失了。但是我仍然得到"authorscard": null作为响应。
英文:
I'm new to go and Backend and I'm Trying to make many-to-many relation between tables. I used this repo to make model:https://github.com/harranali/gorm-relationships-examples/tree/main/many-to-many
I Used GORM with postgresql.
My model:
type Book struct {
gorm.Model
Title string `json:"title"`
Author string `json:"author"`
Description string `json:"description"`
Category string `json:"Category"`
Publisher string `json:"publisher"`
AuthorsCard []*AuthorsCard `gorm:"many-to-many:book_authorscard;" json:"authorscard"`
}
type AuthorsCard struct {
gorm.Model
Name string `json:"name"`
Age int `json:"age"`
YearOfBirth int `json:"year"`
Biography string `json:"biography"`
}
After connecting to database and AutoMigrating:
func init() {
config.Connect()
db = config.GetDB()
db.AutoMigrate(&models.Book{}, &models.AuthorsCard{})
}
I've created Function to see how that relation works:
func TestCreate() {
var AuthorsCard = []models.AuthorsCard{
{
Age: 23,
Name: "test",
YearOfBirth: 1999,
Biography: "23fdgsdddTEST",
},
}
db.Create(&AuthorsCard)
var testbook = models.Book{
Title: "Test",
Author: "tst",
Description: "something",
}
db.Create(&testbook)
db.Model(&testbook).Association("AuthorsCard").Append(&AuthorsCard)
}
But got This Error:
panic: reflect: call of reflect.Value.Interface on zero Value [recovered]
panic: reflect: call of reflect.Value.Interface on zero Value
How can I deal with this "Null" problem and make proper relation?
UPD: The First part of a problem was connected to a version of GORM, After I changed old version(github.com/jinzhu/gorm v1.9.16) to new version (gorm.io/gorm v1.23.6) the problem with reflect Error gone.
but now, when I want to create new book, I get this Error:
/go/pkg/mod/gorm.io/driver/postgres@v1.3.7/migrator.go:119 ERROR: there is no unique constraint matching given keys for referenced table "authors_cards" (SQLSTATE 42830)
[28.440ms] [rows:0] CREATE TABLE "book_authorscard" ("book_id" bigint,"authors_card_id" bigint,PRIMARY KEY ("book_id","authors_card_id"),CONSTRAINT "fk_book_authorscard_authors_card" FOREIGN KEY ("authors_card_id") REFERENCES "authors_cards"("id"),CONSTRAINT "fk_book_authorscard_book" FOREIGN KEY ("book_id") REFERENCES "books"("id"))
[GIN-debug] [WARNING] Creating an Engine instance with the Logger and Recovery middleware already attached.
UPD 2:
I decided to make a Migrator().DropTable(). That's kinda worked, and all Errors have gone. But still I get "authorscard": null as a response.
答案1
得分: 1
通过阅读 Gorm v2 的发布说明(https://gorm.io/docs/v2_release_note.html),我认为你正在尝试使用一个旧版本(<v2)的 Gorm 来使用 v2 的功能。请尝试使用 Gorm 的最新版本。
英文:
By reading the release note of Gorm v2 (https://gorm.io/docs/v2_release_note.html), I think that you are trying to use v2 feature with an old version (<v2). Try to use Gorm latest version.
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