golang gorm reference two columns to same table, problem with insert

Question

original idea was to build rbac analog from yii https://github.com/yiisoft/yii2/blob/master/framework/rbac/migrations/schema-pgsql.sql

so, i have these two models:

type AuthItem struct {
    ID          uint   `gorm:"uniqueIndex;primaryKey;auto_increment;column:id" json:"id"`
    Name        string `gorm:"uniqueIndex;primaryKey;not null;type:varchar(64);column:name" json:"name"`
    ItemType    int64  `gorm:"type:smallint;not null;column:item_type" json:"item_type"`
    Description string `gorm:"size:255;column:description" json:"description"`
}

type AuthRelations struct {
    gorm.Model
    Parent AuthItem `gorm:"references:id;foreignKey:parent;column:parent" json:"parent"`
    Child  AuthItem `gorm:"references:id;foreignKey:child;column:child" json:"child"`
}

also i already have some data in auth_items table and i want to make insert into auth_relations table with GORM, and its looks like this:

var relation = models.AuthRelations{
    Parent: models.AuthItem{ID: 1},
    Child:  models.AuthItem{ID: 2},
}

err = db.Save(&relation).Error
if err != nil {
    log.Fatalf("cant insert: %v", err)
}

i getting this error:

failed to set value 0x1 to field Parent; failed to set value 0x1 to field Parent 

i tried to use gorm function Value(), something like:

func (item AuthItem) Value() (driver.Value, error) {
    return int64(item.ID), nil 
}

and after i implement this function db.Save works, but the constraints/foreignKeys/references stop working

so my question: is there any options to make relations like this in right way or how can i use value() function without loosing constraints ?

Answer 1

i came to conclusion that i need to use many2many relation and here is example for case:

type AuthItem struct {
    ID          uint      `gorm:"uniqueIndex;primaryKey;auto_increment" json:"id"`
    Name        string    `gorm:"unique;not null;type:varchar(64);column:name" json:"name"`
    ItemType    int64     `gorm:"type:smallint;not null;column:item_type" json:"item_type"`
    Description string    `gorm:"size:255;column:description" json:"description"`
    CreatedAt   time.Time `gorm:"default:CURRENT_TIMESTAMP" json:"created_at"`
    UpdatedAt   time.Time `gorm:"default:CURRENT_TIMESTAMP" json:"updated_at"`
    DeletedAt   time.Time `gorm:"default:null" json:"deleted_at"`
}

type AuthRelations struct {
    ID        uint       `gorm:"uniqueIndex;primaryKey;auto_increment" json:"id"`
    Parent    []AuthItem `gorm:"many2many:prnt_authitem_parent;References:Name;constraint:OnUpdate:CASCADE,OnDelete:SET NULL;" json:"parent"`
    Child     []AuthItem `gorm:"many2many:chld_authitem_child;References:Name;constraint:OnUpdate:CASCADE,OnDelete:SET NULL;" json:"child"`
    CreatedAt time.Time  `gorm:"default:CURRENT_TIMESTAMP" json:"created_at"`
    UpdatedAt time.Time  `gorm:"default:CURRENT_TIMESTAMP" json:"updated_at"`
    DeletedAt time.Time  `gorm:"default:null" json:"deleted_at"`
}