Goal
I am trying to setup a simple has_many association with Gorm: a person has many pets.
Problem
I see the following error when I try to save the Person model.
unsupported type []model.Pet, a slice of struct
Details
Assume I want to save an Person that has many Pets.
type Person struct {
UUID `gorm:"PRIMARY_KEY" json:"uuid"`
Pet []Pet `gorm:"foreignkey:PersonUUID:association_foreignkey:UUID"`
}
type Pet struct {
UUID `gorm:"PRIMARY_KEY" json:"uuid"`
PersonUUID string
}
Then I try to create these two models.
personUUID := "dcf4b3c6-d94c-4b2c-9d66-1cbaedd2cc44"
pets := []Pet{
Pet{
UUID: "..",
PersonUUID: personUUID,
}
}
person := Person{
UUID: personUUID,
Pet: Pet,
}
db.Where("uuid = ?", person.UUID).Update(&person)
Then I get the following error.
sql: converting argument $1 type: unsupported type []model.Pet, a slice of struct
Any idea why this might be happening?
I found out it only happens if you use Update instead of Save.
This is odd, because both should work the same way except that Update will try to save the different fields while Save will replace the current values with the new values.
Related
I am new to ORM (and GORM) so apologies if this is an obvious question, but it does not seem to be covered by the documentation.
I will be using the examples from the documentation as a base to my questions
Question 1: Belongs To
// `User` belongs to `Company`, `CompanyID` is the foreign key
type User struct {
gorm.Model
Name string
CompanyID int
Company Company
}
type Company struct {
ID int
Name string
}
A User belongs to one Company only → this is handled by the code
above
A Company has many User → is this implied by the code
above? Or should I add somehow a relation O2M in Company?
Question 2: Has Many
// User has many CreditCards, UserID is the foreign key
type User struct {
gorm.Model
CreditCards []CreditCard
}
type CreditCard struct {
gorm.Model
Number string
UserID uint
}
A User has 1+ CreditCard→ this is handled by the code
A CreditCard can belong to several users (say, a shared family CC) → is it implied? (if not: how to set up the O2M relationship).
Or is it, instead, a case where a CreditCard is explicitly configured to belong to only one user?
Q1: Based on how you defined your structs, you don't need an explicit O2M relationship in the Company struct, but when loading Company details, if you want to load all users that are assigned to that specific company, you need to add that field as well. It will need an additional function call like Preload or Joins, but you shouldn't need an explicit definition of this relationship.
type Company struct {
ID int
Name string
Users []User
}
Q2: The way the relationship is defined now, it is configured so that a CreditCard belongs to only one user. If you want a many2many relationship, you need to specify the relation table. There is more documentation on it here, but it should look something like this:
type User struct {
gorm.Model
CreditCards []CreditCard `gorm:"many2many:users_creditcards"`
}
type CreditCard struct {
gorm.Model
Number string
}
I want to create a model User and Social where the User model has many Socials. Ideally a Social type would also have has one relation to simpilify querying from either side. Here is a code sample:
database type is MySQL 8.0
type base struct {
ID string `json:"id" gorm:"type:char(36);primaryKey;"`
Created time.Time `json:"created" gorm:"autoCreateTime"`
Updated time.Time `json:"updated" gorm:"autoUpdateTime"`
}
type User struct {
base
Friends []*User `json:"friends" gorm:"many2many:friends"`
Socials []*Social `json:"socials"`
}
type Social struct {
base
Provider string `json:"provider" gorm:"type:varchar(32);index"`
Identifier string `json:"identifier" gorm:"type:varchar(32);index"`
User *User `json:"user" gorm:"foreignKey:ID"`
Token string `json:"token"`
Link string `json:"link" gorm:"type:varchar(128)"`
}
Im getting the following error when using db.AutoMigrate(&User{}, &Social{}):
model.Social's field User, need to define a valid foreign key for relations or it need to implement the Valuer/Scanner interface
runtime error: invalid memory address or nil pointer dereference
I have tried:
adding gorm:"foreignKey:ID" to User.Socials tags
not using pointers (eg in User struct Socials []Social instead of Socials []*Social)
but the issue remains
According to documentation (https://gorm.io/docs/has_many.html#Has-Many),
you need to use objects, not references
type User struct {
base
Friends []User `json:"friends" gorm:"many2many:friends"`
Socials []Social `json:"socials"`
}
no * here
Also you can add UserID field to Social
type Social struct {
base
UserID string
Provider string `json:"provider" gorm:"type:varchar(32);index"`
Identifier string `json:"identifier" gorm:"type:varchar(32);index"`
User *User `json:"user" gorm:"foreignKey:ID"`
Token string `json:"token"`
Link string `json:"link" gorm:"type:varchar(128)"`
}
and add
type User struct {
base
FriendOf string `gorm:""`
Friends []*User `json:"friends" gorm:"many2many:friends,foreignKey:FriendOf"`
Socials []*Social `json:"socials"`
}
Issue was here:
type base struct {
...
}
type User {
base
...
}
type Social {
base
...
}
Since I thought base would just be package local definition I messed up the capitalization and had a private primary key.
Another issue was touched on by #vodolaz095, but (imo) not sufficiently clarified for any new go-gorm user.
It does not seem to be possible to use a has one relation like User User be the foreign key for a has many relation like Socials []Social gorm:"foreignKey:User". It is required to be split up as #vodolaz095 displayed in his 2nd code block
I want to make a webapp and I have a simple data model with a one to many relation. I tried sticking to the documentation of gorm and from my understanding this should work:
package dbModels
import "gorm.io/gorm"
type Post struct {
gorm.Model
Text string
Likes int
Comments []Comment
}
type Comment struct {
gorm.Model
Text string
Likes int
PostID uint
}
I'm migrating these models like that:
db.AutoMigrate(&dbModels.Post{}, &dbModels.Comment{})
Then I want to put this object in post:
func (r *mutationResolver) CreatePost(ctx context.Context, input model.PostInput) (*model.Post, error) {
var items []*model.Comment
post := model.Post{
Text: input.Text,
Likes: 0,
Comments: items,
}
r.DB.Create(&post)
return &post, nil
}
however I get the following error:
2021/01/31 11:23:01 /home/felix/Projekte/GoReact/server/graph/schema.resolvers.go:21 invalid field found for struct github.com/blamefelix/TwitterClone/graph/model.Post's field Comments, need to define a valid foreign key for relations or it need to implement the Valuer/Scanner interface
I don't really understand what I'm doing wrong. From the gorm documentation I thought the relation would get managed by gorm if I put it like that? My suspicion is, that I put the wrong data in?
So I've managed to fix it by using the same model for graphql and gorm. The problem must have been that I've pased the wrong data into the db create function
I wanted to create relationnal database structure in a using the go package Gorm.
I wanted to add foreign keys to my structure, it works perfectly on regular field, but it does not seem to work when I want to make foreign key for anonymous fields.
Here is some simplified code to demonstrate my case
type StructA struct {
gorm.Model
SimpleFieldID int // appears in database as foreign key
SimpleField StructB
TranslationID int // appears in database as a regular int
Translation
}
type StructB struct {
gorm.Model
SomeField string
SomeOtherField string
}
type Translation struct {
gorm.Model
En string
Fr string
}
I wanted to have anonymous field in the first place to be able to call some GetName() method on any object that has the Translation attribute.
I found this question, but the given anwser was for the has-one relation, where I want to use a belongs-to relation.
I use go-swagger. I have model like:
// Pet pet
// swagger:model
type Pet struct {
// id
ID int64 `json:"id,omitempty"`
// name
// Required: true
Name *string `json:"name"`
}
and for example in my POST field Name have to be required but for GET not. So how should I add it if I don't want create similar model without required? Because for now my only thought is to create type PetGET struct and type PetPOST struct which, I guess is stupid idea.
If you're generating spec from code, then having a PetGET and PetPOST is not a stupid idea. Usually the program model doesn't match the API model, and you have to repeat definitions just to generate the spec right. So you have a couple of options here:
You can simply mark the field required: false, and deal with it in the GET handler.
If you're generating spec from code, you can create swagger-only models separate from your program models, and for cases like this, create two models with different annotations.