How To Use Embedding To Get Data From A Table - go

Question

I am a PHP programmer and I have just learned Golang for weeks. I am writing REST API to get post information from my 'posts' table. I have the FindPostByID method in posts_controller. This controller uses Post struct which is model
func (p *Post) FindPostByID(db *gorm.DB, pid uint64) (*Post, error) {
var err error
err = db.Debug().Model(&Post{}).Where("id = ?", pid).Take(&p).Error
if err != nil {
return &Post{}, err
}
if p.ID != 0 {
err = db.Debug().Model(&User{}).Where("id = ?", p.AuthorID).Take(&p.Author).Error
if err != nil {
return &Post{}, err
}
}
return p, nil
}
But now I want to add method FindByID into parent struct, such as ParentModel because when I have articles_controller I can use FindByID method in parent struct to get an article info. So I have the following code in parent struct
type ParentModel struct {
}
func (m *ParentModel) FindByID(db *gorm.DB, uid uint64) (*ParentModel, error) {
var err error
err = db.Debug().Model(ParentModel{}).Where("id = ?", uid).Take(&m).Error
if err != nil {
return &ParentModel{}, err
}
if gorm.IsRecordNotFoundError(err) {
return &ParentModel{}, errors.New("User Not Found")
}
return m, err
}
And I change in the Post struct like following:
type Post struct {
ParentModel
ID uint64 `gorm:"primary_key;auto_increment" json:"id"`
Title string `gorm:"size:255;not null;unique" json:"title"`
Content string `gorm:"size:255;not null;" json:"content"`
Author User `json:"author"`
AuthorID uint32 `sql:"type:int REFERENCES users(id)" json:"author_id"`
CreatedAt time.Time `gorm:"default:CURRENT_TIMESTAMP" json:"created_at"`
UpdatedAt time.Time `gorm:"default:CURRENT_TIMESTAMP" json:"updated_at"`
}
I change FindPostByID method in posts_controller as well:
func (server *Server) GetPost(w http.ResponseWriter, r *http.Request) {
vars := mux.Vars(r)
pid, err := strconv.ParseUint(vars["id"], 10, 64)
if err != nil {
responses.ERROR(w, http.StatusBadRequest, err)
return
}
post := models.Post{}
postReceived, err := post.FindByID(server.DB, pid)
if err != nil {
responses.ERROR(w, http.StatusInternalServerError, err)
return
}
responses.JSON(w, http.StatusOK, postReceived)
}
When I run my program, have the err: Table 'golang_rest_api.parent_models' doesn't exist.
How I can do to use inheritance method like PHP language

Answer 1

The error Table 'golang_rest_api.parent_models' doesn't exist means that no table named parent_models exists in your database.
This is because gorm by default uses the pluralised camelcase name of your struct, which you supplied in gorm's Model() method, as its table's name.
Gorm provides in-built support for many kinds of associations which you can find here. I would also like to ask you to complete your ParentModel struct's definition. It's empty right now.