Troubles with Eloquent

Question

I'm rather new to Eloquent (and ORM's as a whole really). I have done rather a lot of background reading but can't quite get my head around the relationships in Eloquent.

I have a Car model that relates to a Color model, a Make model and a Model model.

I pass my Car::getAll() through to my View as $cars. When I call dd(toArray($cars)) I get the following:

array (size=1)
  0 => 
    array (size=12)
      'id' => string '1' (length=1)
      'registration' => string '123' (length=3)
      'make' => 
        array (size=5)
          'id' => string '1' (length=1)
          'title' => string 'Ford' (length=4)
          'slug' => string 'ford' (length=4)
          'created_at' => string '2014-06-26 21:30:23' (length=19)
          'updated_at' => string '2014-06-26 21:30:23' (length=19)
      'model' => 
        array (size=5)
          'id' => string '1' (length=1)
          'title' => string 'Mustang' (length=7)
          'slug' => string 'mustang' (length=7)
          'created_at' => string '2014-06-26 21:30:41' (length=19)
          'updated_at' => string '2014-06-26 21:30:41' (length=19)
      'color' => 
        array (size=5)
          'id' => string '1' (length=1)
          'title' => string 'Red' (length=3)
          'slug' => string 'red' (length=3)
          'created_at' => string '2014-06-26 21:30:03' (length=19)
          'updated_at' => string '2014-06-26 21:30:03' (length=19)
      'year' => string '1991' (length=4)
      'is_classic' => string '1' (length=1)
      'price' => string '999.00' (length=6)
      'sold' => string '0' (length=1)
      'active' => string '1' (length=1)
      'created_at' => string '2014-06-26 22:17:27' (length=19)
      'updated_at' => string '2014-06-26 22:17:27' (length=19)`

Which appears to be right to me, however when I have:

foreach ($cars as $car) {
  echo $car->color-title;
}

I get a "Trying to get property of non-object" error.

My Models are as follows:

Car.php

class Car extends \Eloquent {
    protected $fillable = ['color_id'];


    public function color() {
        return $this->belongsTo('Color', 'id');
    }

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

    public function make() {
        return $this->belongsTo('Make', 'id');
    }

    public static function getAll() {
        return Car::with('color', 'make', 'model')->where('active', 1)->get();
    }
}

Color.php

class Color extends \Eloquent {
    protected $fillable = ['title', 'slug'];

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

Make.php

class Make extends \Eloquent {
    protected $fillable = [];

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

Model.php

class Model extends \Eloquent {
    protected $fillable = [];

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

Any help would be very much appreciated. Thank you

EDIT:

Sorry I should have included my schema up methods:

CreateMakesTable

public function up()
    {
        Schema::create('makes', function(Blueprint $table)
        {
            $table->increments('id');
            $table->string('title');
            $table->string('slug');
            $table->timestamps();
        });
    }

CreateModelsTable

public function up()
    {
        Schema::create('models', function(Blueprint $table)
        {
            $table->increments('id');
            $table->integer('make')->unsigned();
            $table->string('title');
            $table->string('slug');
            $table->timestamps();
        });

        Schema::table('models', function(Blueprint $table)
        {
            $table->foreign('make')->references('id')->on('makes')->onDelete('cascade');
        });
    }

CreateColorsTable

public function up()
    {
        Schema::create('colors', function(Blueprint $table)
        {
            $table->increments('id');
            $table->string('title');
            $table->string('slug');
            $table->timestamps();
        });
    }

CreateCarsTable

public function up()
    {
        Schema::create('cars', function(Blueprint $table)
        {
            $table->increments('id');
            $table->string('registration');
            $table->integer('make')->unsigned();
            $table->integer('model')->unsigned();
            $table->integer('year');
            $table->integer('color')->unsigned();
            $table->boolean('is_classic');
            $table->float('price');
            $table->boolean('sold');
            $table->boolean('active');
            $table->timestamps();
         });

         Schema::table('cars', function(Blueprint $table)
         {
            $table->foreign('make')->references('id')->on('makes')->onDelete('cascade');
            $table->foreign('model')->references('id')->on('models')->onDelete('cascade');
            $table->foreign('color')->references('id')->on('colors')->onDelete('cascade');
         });
    }

Answer 1

Like Jason pointed out the error is caused by null returned from one of those relationships. But the problem with your setup is, that the relationship definitions are wrong.

So first make them right:

// it goes like this:
// belongsTo('Model', 'foreign_key_on_this_model', 'primary_key_on_related')

public function color() {
    return $this->belongsTo('Color', 'color'); // primary key is id so no need to specify
}

hasMany relations on the other models are OK.

Then in that loop:

foreach ($cars as $car)
{
   if (count($car->color))
   {
       // do something with color
   }
}

For the reason I'm using count read this: Laravel check if related model exists

You can also return only cars that have related color, make and whatever you need like below:

$cars = Car::has('color')->has('make')...