Retrieving relationships of relationships using Eloquent in Laravel

Question

I have a database with the following tables and relationships:

Advert 1-1 Car m-1 Model m-1 Brand

If I want to retriev

Answer 1

It's in the official documentation under "Eager Loading"

Multiple relationships:

$books = Book::with('author', 'publisher')->get();

Nested relationships:

$books = Book::with('author.contacts')->get();

So for you:

Advert::find(1)->with('Car.Model')->get();

Answer 2

Suppose you have 3 models region,city,hotels and to get all hotels with city and region then

Define relationship in them as follows:-

Hotel.php

class Hotel extends Model {

  public function cities(){
        return $this->hasMany(City::class);
  }

  public function city(){
        return $this->belongsTo('App\City','city_id');
  }
}

City.php

class City extends Model {

  public function hotels(){
      return $this->hasMany(Hotel::class);
  }

  public function regions(){
      return $this->belongsTo('App\Region','region_id');    
  }
}

Region.php

class Region extends Model
{

  public function cities(){
      return $this->hasMany('App\City');    
  }

  public function country(){
      return $this->belongsTo('App\Country','country_id');
  } 
}

HotelController.php

public function getAllHotels(){
    // get all hotes with city and region
    $hotels = Hotel::with('city.regions')->get()->toArray();

}

Answer 3

First you need to create your relations,

<?php

class Advert extends Eloquent {

    public function car()
    {
        return $this->belongsTo('Car');
    }

}

class Car extends Eloquent {

    public function model()
    {
        return $this->belongsTo('Model');
    }

}

class Model extends Eloquent {

    public function brand()
    {
        return $this->belongsTo('Brand');
    }

    public function cars()
    {
        return $this->hasMany('Car');
    }

}

class Brand extends Eloquent {

    public function models()
    {
        return $this->hasMany('Model');
    }

}

Then you just have to access this way:

echo Advert::find(1)->car->model->brand->name;

But your table fields shoud be, because Laravel guess them that way:

id (for all tables)
car_id
model_id
brand_id

Or you'll have to specify them in the relationship.