How to get double nested data with gorm? - go

Question

I am developing an application that manages quotes using go and gorm. Users create quote, quotes have multiple tags, and users can add quotes to their favorites.
I want to get a list of quotes that a user has added to their favorites. And at that time, I want to get the tag attached to the quotes.
Here is my data models.
type Quote struct {
ID int `gorm:"primary_key" json:"id"`
CreatedAt time.Time `json:"created_at"`
UpdatedAt time.Time `json:"updated_at"`
Text string `json:"text"`
Page int `json:"page"`
Published bool `gorm:"default:false" json:"published"`
Tags []Tag `gorm:"many2many:quotes_tags;" json:"tags"`
User User `json:"user"`
UserID string `json:"user_id"`
FavoriteUsers []User `gorm:"many2many:users_quotes;" json:"favorite_users"`
}
type User struct {
ID string `json:"id"`
CreatedAt time.Time `json:"created_at"`
UpdatedAt time.Time `json:"updated_at"`
Username string `json:"username"`
Quotes []Quote `json:"quotes"`
FavoriteQuotes []Quote `gorm:"many2many:users_quotes;" json:"favorite_quotes"`
}
type Tag struct {
ID int `gorm:"primary_key" json:"id"`
CreatedAt time.Time `json:"created_at"`
Name string `json:"name"`
}
I tried the following and got the favorite quote, but the tags was null. Is there a way to do this with gorm? Thank you in advance.
func (service *Service) GetUser(uid string) (models.User, error) {
fmt.Println(uid)
user := models.User{}
if result := service.db.Preload(clause.Associations).First(&user, "id = ?", uid); result.Error != nil {
return models.User{}, result.Error
}
return user, nil
}
func (service *Service) GetFavoriteQuotes(uid string) ([]models.Quote, error) {
user, err := service.GetUser(uid)
if err != nil {
return []models.Quote{}, err
}
return user.FavoriteQuotes, nil
}

Answer 1

If you check the Preload All documentation, it says:
clause.Associations won’t preload nested associations, but you can use it with Nested Preloading
In your case, this would be something like this:
if result := service.db.Preload("FavoriteQuotes.Tags").Preload(clause.Associations).First(&user, "id = ?", uid); result.Error != nil {
return models.User{}, result.Error
}