Laravel 8.x, 3 models and many to many relationship - laravel

Question

I am new to laravel and trying the following:
I have these tables:
disciplines: id | name
specialties: id | name
categories: id | name
discipline_specialty (pivot table): id | discipline_id | specialties_id
Discipline model:
public function specialties()
{
return $this->belongsToMany(Specialty::class);
}
Specialty model:
public function disciplines()
{
return $this->belongsToMany(Discipline::class);
}
My question is:
how can I relate (many to many) the categories to the pivot table discipline_specialty in order to access the category name with the discipline and specialty ids?
I had thought of an additional pivot table that linked category id and discipline_specialty id but I don't know if it's the best solution and how to do it. Do you have any suggestions? Any help is appreciated.

Answer 1

You can introduce a junction/pivot model that will relate these 3 relations as many-to-one/belongsTo and one-to-many/hasMany from Discipline/Speciality/Category.
Discipline Speciality Category
\\ || //
\\ || //
DisciplineSpecialityCategory
This DisciplineSpecialityCategory model will have following attributes or FKs
Table: discipline_speciality_category
discipline_id
speciality_id
category_id
Now you model definitions will be like
class Discipline extends Model
{
public function disciplineSpecialityCategory()
{
return $this->hasMany(DisciplineSpecialityCategory::class, 'id', 'discipline_id');
}
}
class Speciality extends Model
{
public function disciplineSpecialityCategory()
{
return $this->hasMany(DisciplineSpecialityCategory::class, 'id', 'speciality_id');
}
}
class Category extends Model
{
public function disciplineSpecialityCategory()
{
return $this->hasMany(DisciplineSpecialityCategory::class, 'id', 'category_id');
}
}
class DisciplineSpecialityCategory extends Model
{
public function discipline()
{
return $this->belongsTo(Discipline::class, 'id', 'discipline_id');
}
public function speciality()
{
return $this->belongsTo(Speciality::class, 'id', 'speciality_id');
}
public function category()
{
return $this->belongsTo(Category::class, 'id', 'category_id');
}
}