Retrieving Parents and Children - Self Referencing Entity gorm - parent

Question

I have a table that have a hierarchy structure with a parent having many children and a children having many parents.
As an example the following struct:
type User struct {
gorm.Model
Name string
SubUsers []*User `gorm:"many2many:user_sub_users;constraint:OnDelete:CASCADE"`
SuperUsers []*User `gorm:"many2many:user_sub_users.......` // no idea what to fill here
}
What's the gorm configuration I need to add to being able to retrieve the super users (parents) for one entity?
So, as an example, imagine that I have the following
Table users
| ID | name |
--------------=
| 1 | Alice |
| 2 | Bob |
| 3 | Joe |
| 4 | Manuel |
---------------
Table users_sub_users
| ID | user_id | sub_user_id |
-------------------------------
| 1 | 1 | 2 |
| 2 | 1 | 3 |
| 3 | 4 | 1 |
-------------------------------
So if I retrieve the user Alice, I want to get the following:
Alice ->
SubUsers: [Bob, Joe]
SuperUsers: [Manuel]

Answer 1

You can specify the fields in the table user_sub_users with joinForeignKey and joinReferences.
Instead of:
SubUsers []*User `gorm:"many2many:user_sub_users"`
it would be more explicit:
SubUsers []*User `gorm:"many2many:user_sub_users;joinForeignKey:sub_user_id;joinReferences:user_id;"`
For the SuperUsers just swap the fields:
SuperUsers []*User `gorm:"many2many:user_sub_users;joinForeignKey:user_id;joinReferences:sub_user_id;"`
Minimal example:
package main
import (
"fmt"
"github.com/glebarez/sqlite"
"gorm.io/gorm"
)
type User struct {
gorm.Model
Name string
SubUsers []*User `gorm:"many2many:user_sub_users;joinForeignKey:sub_user_id;joinReferences:user_id;"`
SuperUsers []*User `gorm:"many2many:user_sub_users;joinForeignKey:user_id;joinReferences:sub_user_id;"`
}
func main() {
db, err := gorm.Open(sqlite.Open("test.db"), &gorm.Config{})
if err != nil {
panic(err)
}
db.AutoMigrate(&User{})
alice := &User{Name: "Alice"}
db.Create(alice)
bob := &User{Name: "Bob"}
db.Create(bob)
joe := &User{Name: "Joe"}
db.Create(joe)
manuel := &User{Name: "Manuel"}
db.Create(manuel)
err = db.Model(alice).Association("SubUsers").Append(bob, joe)
if err != nil {
panic(err)
}
err = db.Model(manuel).Association("SubUsers").Append(alice)
if err != nil {
panic(err)
}
var user User
err = db.Preload("SubUsers").Preload("SuperUsers").First(&user, alice.ID).Error
if err != nil {
panic(err)
}
for _, u := range user.SubUsers {
fmt.Println("Subuser", u.Name)
}
for _, u := range user.SuperUsers {
fmt.Println("Superuser", u.Name)
}
}