英文:
Gorm belongs to does not return relations
问题
我有以下这些模型：
type Message struct {gorm.ModelUserID uint `json:"userId"`User userModels.UserContent string `json:"content"`}type Receiver struct {gorm.ModelUserID uint `json:"userId"`User userModels.UserFirstName string `json:"firstName"`LastName string `json:"lastName"`Email string `json:"email"`Address string `json:"address"`Phone string `json:"phone"`}type Delivery struct {gorm.ModelMessage Message `json:"message"`MessageID uint `json:"messageId"`Receiver Receiver `json:"receiver"`ReceiverID uint `json:"receiverId"`DeliveryDate time.Time `json:"deliveryDate"`Sent bool `json:"sent"`}
我在数据库中插入了一些具有特定MessageID和ReceiverID的Delivery。当我查询该特定Delivery时，我期望得到相应的Message和具有ReceiverID的Receiver。
但是我得到的是一个既没有Message对象也没有Receiver对象的Delivery。
以下是我得到的结果：
{"ID": 2,"CreatedAt": "2021-08-26T04:44:33.366628+04:30","UpdatedAt": "2021-08-26T04:44:33.366628+04:30","DeletedAt": null,"message": {"ID": 0,"CreatedAt": "0001-01-01T00:00:00Z","UpdatedAt": "0001-01-01T00:00:00Z","DeletedAt": null,"userId": 0,"User": {"ID": 0,"CreatedAt": "0001-01-01T00:00:00Z","UpdatedAt": "0001-01-01T00:00:00Z","DeletedAt": null,"firstName": "","lastName": "","email": "","password": "","country": "","dateOfBirth": "0001-01-01T00:00:00Z","rank": "","gender": "","plan": ""},"content": ""},"messageId": 2,"Receiver": {"ID": 0,"CreatedAt": "0001-01-01T00:00:00Z","UpdatedAt": "0001-01-01T00:00:00Z","DeletedAt": null,"userId": 0,"User": {"ID": 0,"CreatedAt": "0001-01-01T00:00:00Z","UpdatedAt": "0001-01-01T00:00:00Z","DeletedAt": null,"firstName": "","lastName": "","email": "","password": "","country": "","dateOfBirth": "0001-01-01T00:00:00Z","rank": "","gender": "","plan": ""},"firstName": "","lastName": "","email": "","address": "","phone": ""},"receiverId": 1,"deliveryDate": "2021-08-25T05:18:27.950457+04:30","sent": false}
而我期望它返回我指定的messageId的Message和具有ReceiverID的Receiver。
英文:
I have these models
type Message struct {gorm.ModelUserID uint `json:"userId"`User userModels.UserContent string `json:"content"`}type Receiver struct {gorm.ModelUserID uint `json:"userId"`User userModels.UserFirstName string `json:"firstName"`LastName string `json:"lastName"`Email string `json:"email"`Address string `json:"address"`Phone string `json:"phone"`}type Delivery struct {gorm.ModelMessage Message `json:"message"`MessageID uint `json:"messageId"`Receiver Receiver `json:"Receiver"`ReceiverID uint `json:"receiverId"`DeliveryDate time.Time `json:"deliveryDate"`Sent bool `json:"sent"`}
I insert some Delivery in the database with certain MessageID and ReceiverID. When I query that certain Delivery I expect to get the regarding message with the id of MessageID, and a Receiver of id ReceiverID.
But what I get is a Delivery with both empty Message and Receiver objects.
this is what I get:
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{"ID": 2,"CreatedAt": "2021-08-26T04:44:33.366628+04:30","UpdatedAt": "2021-08-26T04:44:33.366628+04:30","DeletedAt": null,"message": {"ID": 0,"CreatedAt": "0001-01-01T00:00:00Z","UpdatedAt": "0001-01-01T00:00:00Z","DeletedAt": null,"userId": 0,"User": {"ID": 0,"CreatedAt": "0001-01-01T00:00:00Z","UpdatedAt": "0001-01-01T00:00:00Z","DeletedAt": null,"firstName": "","lastName": "","email": "","password": "","country": "","dateOfBirth": "0001-01-01T00:00:00Z","rank": "","gender": "","plan": ""},"content": ""},"messageId": 2,"Receiver": {"ID": 0,"CreatedAt": "0001-01-01T00:00:00Z","UpdatedAt": "0001-01-01T00:00:00Z","DeletedAt": null,"userId": 0,"User": {"ID": 0,"CreatedAt": "0001-01-01T00:00:00Z","UpdatedAt": "0001-01-01T00:00:00Z","DeletedAt": null,"firstName": "","lastName": "","email": "","password": "","country": "","dateOfBirth": "0001-01-01T00:00:00Z","rank": "","gender": "","plan": ""},"firstName": "","lastName": "","email": "","address": "","phone": ""},"receiverId": 1,"deliveryDate": "2021-08-25T05:18:27.950457+04:30","sent": false}
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While I expect it to return the message with the messageId I specified and also the receiver
答案1
得分: 2
当我查询特定的交付时，你好。如果你使用Preload，你将获得接收者和消息的详细信息。如果你不使用Preload，你将得到一个包含空消息和接收者对象的交付对象。如果你只需要消息ID和接收者ID，你应该将Message Message更改为Message *Message，将Receiver Receiver更改为Receiver *Receiver。如果你使用Preload，结果与上述相同。如果你不使用Preload，接收者和消息将为nil。以下是所有的测试代码和调试信息：
type User3 struct {gorm.ModelName string}type Message struct {gorm.ModelUserID uint `json:"userId"`User *User3Content string `json:"content"`}type Receiver struct {gorm.ModelUserID uint `json:"userId"`User *User3FirstName string `json:"firstName"`LastName string `json:"lastName"`Email string `json:"email"`Address string `json:"address"`Phone string `json:"phone"`}type Delivery struct {gorm.ModelMessage *Message `json:"message"`MessageID uint `json:"messageId"`Receiver *Receiver `json:"receiver"`ReceiverID uint `json:"receiverId"`DeliveryDate time.Time `json:"deliveryDate"`Sent bool `json:"sent"`}func main() {db := config.CreateMysql()db.AutoMigrate(Delivery{})d := Delivery{Message: &Message{User: &User3{Name: "a"},Content: "hello b~",},Receiver: &Receiver{User: &User3{Name: "b"},},DeliveryDate: time.Now(),Sent: false,}db.Create(&d)d2 := Delivery{}db.First(&d2)fmt.Printf("%v\n", d2)d3 := Delivery{}db.Preload("Message").Preload("Receiver").First(&d3)fmt.Printf("%v\n", d3)}
上述用户为nil，如果你想预加载嵌套关联，请使用以下方式：.Preload("Message.User")。详细信息请参考：https://gorm.io/docs/preload.html
英文:
When I query that certain Delivery
how do you do?
if you uses Preload
db.Preload("Message").Preload("Receiver").First(&d3)
you will get the deltial of Receiver and message like
if you don't uses Preload
what you get is a Delivery with both empty Message and Receiver objects.
if you only need messageId and receiverID
you should change the Message Message to Message *Message and Receiver Receiver to Receiver *Receiver
if you uses Preload -> same to above
if you don't uses Preload -> Receiver and Message will be nil
follow is all test code and debug info:
type User3 struct {gorm.ModelName string}type Message struct {gorm.ModelUserID uint `json:"userId"`User *User3Content string `json:"content"`}type Receiver struct {gorm.ModelUserID uint `json:"userId"`User *User3FirstName string `json:"firstName"`LastName string `json:"lastName"`Email string `json:"email"`Address string `json:"address"`Phone string `json:"phone"`}type Delivery struct {gorm.ModelMessage *Message `json:"message"`MessageID uint `json:"messageId"`Receiver *Receiver `json:"Receiver"`ReceiverID uint `json:"receiverId"`DeliveryDate time.Time `json:"deliveryDate"`Sent bool `json:"sent"`}func main() {db := config.CreateMysql()db.AutoMigrate(Delivery{})d := Delivery{Message: &Message{User: &User3{Name: "a"}, Content: "hello b~"}, Receiver: &Receiver{User: &User3{Name: "b"}}, DeliveryDate: time.Now(), Sent: false}db.Create(&d)d2 := Delivery{}db.First(&d2)fmt.Printf("%v\n", d2)d3 := Delivery{}db.Preload("Message").Preload("Receiver").First(&d3)fmt.Printf("%v\n", d3)}
ps: above user is nil, if you want preload nested associations, uses follow:
.Preload("Message.User")
https://gorm.io/docs/preload.html
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