I have these 2 structs
type User struct {
gorm.Model
Name string
CompanyID int
Company Company
}
type Company struct {
gorm.Model
Name string
Adress string
}
I want to get users and preload their companies but I don't want to get the Adress field I tried the custom preload like bellow and I tested it in postman . the query returned all the fields but for adress I get an empty string , the reason why this is happening is that when storing the result in the user struct golang automatically initialize all the fields and the field adress get returned with its initial value which is an empty sting
var user []User
db.Table("users").Preload("Company",func(db *gorm.DB) *gorm.DB {
return db.Select("ID" ,"Name")
}).Find(&user)
what should I do to only have the name and id but not the adress
If your server exports the result as json you could add the json tag omitempty as such:
type Company struct {
gorm.Model
Name string
Adress string `json:"omitempty"`
}
That way the address field will not be included if it is an empty string.
Related
I have this model struct:
type User struct {
ID uint `json:"id" gorm:"primaryKey"`
Name string `json:"name"`
BirthDate datatypes.Date `json:"birthDate" gorm:"default:null"`
}
In field BirthDate I am using custom data type datatypes.Date provided by Gorm
The problem is, it shows this value 0001-01-01T00:00:00Z in json response, while inside the database the value of BirthDate is null.
What I want is it should result in empty string if null, How to achive that?
I'm new to Golang and Gorm, and I couldn't find the anwswer. In a rest api, I want my json to come with values from the one table relation.
type Product struct {
gorm.Model
Name string
Description string
Weight string
TypeID uint
}
type Type struct {
ID string `gorm:"primaryKey;"`
Name string
Product []Product
}
and I want my Product json to come with the ID and Name from Type.
but this doesn't work.
var product Product
id:=1
db.Preload("Type").First(&product, id)
Do I have to do something like this in the struct?
type Product struct {
gorm.Model
Name string
Description string
Weight string
Type Type
}
If you want to load Type.ID and Type.Name into Product.ID and Product.Name, you need to specifically select fields from two tables:
var product Product
id:=1
db.Joins("JOIN types ON types.id = products.type_id"). Select("types.id, types.name, products.description, products.weight, products.type_id").First(&product, id)
If you want to separate Type fields into a separate field in the Product struct, you need to make the following changes:
type Product struct {
gorm.Model
Name string
Description string
Weight string
TypeID uint
Type Type
}
var product Product
id:=1
db.Preload("Type").First(&product, id)
Here, all of the Type fields will be loaded into the Product.Type field.
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 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.
There are two model use gorm in my project as following:
type User struct {
gorm.Model
Name string `gorm:"type:varchar(128)" json:"name"`
}
type Service struct {
gorm.Model
Name string `gorm:"type:varchar(128)" json:"name"`
Members []*User `gorm:"many2many:user_to_service;" json:"members"`
}
Now, I need to add a field role in the user_to_service, represent the user role in the service such as admin, member, guest and so on.
How do I add the role field in user_to_service? And How to update or query with this field use gorm?