Trouble understanding Eloquent relationships - laravel

Question

I'm having trouble understanding Eloquent relationships.
Say I have four tables with data
Users
id
...
UserCars
user_id
car_id
color_id
Cars
id
make
model
Colors
id
color
Now I understand how to get the UsersCars for a selected user with
User.php Model
public function cars()
{
$this->hasMany(Car::class);
}
I can then get the User's car in to a view with
public function show(User $user)
{
$cars= $user->cars;
return $cars;
}
So say a given user id 1 has 2 cars, I can get get his cars with $user->cars() which gives me something like in the view
{"id":1, "car_id":3, "color_id": 2}
{"id":1, "car_id":10, "color_id": 4}
But what I'm not getting is how to then further get the actual value of the relevant ids. So once I've passed $users->cars() as $cars in my controller to my view I can then get the actual make and model and color of the users car.
Something like
#foreach ($cars as $car)
{{ $car->make }} : {{ $car->model }}
{{ $car->color }}
#endforeach
So once I call $user->cars() I need the something like
{"id":1, "car_id":3, "make" => "Ford", "model" => "Fiesta", "color_id": 2, "color":"red"}
{"id":1, "car_id":10, "make" => "Volkswagon", "model" => "Golf", "color_id": 4, "color":"blue"}
I hope that makes sense and any help is appreciated, thanks.

Answer 1

You can access all that data through relationships. Simply define them and load them as you need. First let's define every basic relationship in your model files
In Users model:
// User.php
public function user_cars()
{
return $this->hasMany(App\UserCar::class);
}
In UserCars model:
// UserCar.php
public function user()
{
return $this->belongsTo(App\User::class);
}
public function car()
{
return $this->belongsTo(App\Car::class);
}
public function color()
{
return $this->belongsTo(App\Color::class);
}
In Cars model:
// Car.php
public function user_cars()
{
return $this->hasMany(App\UserCar::class);
}
With all that defined, you can access the relationships by just calling upon them. The difference between $car->user_cars() and $car->user_car is the returned object.
$car->user_cars() is an instance HasMany object and $car->user_cars is a Collection instance. It's basically the same as writing $car->user_cars()->get() so you want to go with the later most of the time.
Now let's see your controller method. Technically, you can return the $user and access all relationships in the view but every time you do, that's an additional query to the database. It's something you should avoid by getting all the data eager loaded first. Since you're using Route Model Binding to get the $user, you need to use the load() function. You can even load nested relationships, which is exactly what you're looking for.
public function show(User $user)
{
// This tells eloquent to add the nested relationships to your User instance.
$user->load('user_cars.car', 'user_cars.color');
return $user;
}
Next, you can access them in the view just like you wanted
#foreach ($user->user_cars as $user_car)
{{ $user_car->car->make }}
{{ $user_car->car->model }}
{{ $user_car->color->color }}
#endforeach
Read more on the subject https://laravel.com/docs/5.8/eloquent-relationships

Answer 2

Your have incorrectly defined the relationship on the User to Car.
Since the relationship with users and cars are many-to-many you must use belongsToMany() eloquent relationship.
doc => https://laravel.com/docs/5.8/eloquent-relationships#many-to-many
User Model
public function cars()
{
return $this->belongsToMany(Car::class, 'user_cars', 'user_id', 'car_id');
}
Car Model
public function users()
{
return $this->belongsToMany(User:class, 'user_cars', 'car_id', 'user_id');
}
then you can access cars from the user, or users from the car.