Laravel 8 - I have an error in when using method in Model when using paratheses with the method-CodePudding

I have two models [The relation is one-many / Category-Trip]:

Category Model Code:

class Category extends Model
{
    use HasFactory;

    protected $fillable = [
            'id',
            'category_name',
            'category_desc',
            'category_img',
        ];


    public function trip() {
        return $this->hasMany(Trip::class);
    }

}

Trip Model Code:

class Trip extends Model
{
    use HasFactory;

    protected $fillable = [
        'name',
        'description',
        'max_visitors',
        'price',
        'date',
        'image',
        'guide_id',
        'category_id',
    ];

    public function category()
    {
        return $this->belongsTo(Category::class);
    }
}

when I use this code, I will get this error:

TypeError Symfony\Component\HttpFoundation\Response::setContent(): Argument #1 ($content) must be of type ?string, Illuminate\Database\Eloquent\Relations\BelongsTo given, called in C:\Users\Orange\Desktop\ON GITHUB\Tours-Booking\vendor\laravel\framework\src\Illuminate\Http\Response.php on line 72

$trip = Trip::findOrFail(1);
return $trip->category();

But when write this without paratheses, i will not get this error, what is the problem?

$trip = Trip::findOrFail(1);
return $trip->category;

CodePudding user response：

As a user explained (but not fully):

You are returning a relationship in your controller, but that is not valid (based on the error). Because BelongsTo cannot be serialized to a string, it tries to return the BelongsTo object, hence giving you that error (look, it is saying it is wanting null or a string, but you are returning BelongsTo).

When you do $model->relation (without ()), that means it will try to get all the data that satisfies the relation and store it as a Category in $model->relation (because it is a BelongsTo), but when you use $model->relation() you creating a query so you can query the relation with whatever you want/need, like $model->relation()->where('status', 'Active')->get()...

You have 2 solutions: either return $trip->category (it is going to be a Category object/model) or $trip->category()->get() or any query but use ->get() (will return a Collection) or ->first() (will return a Category model) at the end...

Read the documentation again so you understand better now: Relationships and First vs Get and BelongsTo documentation.

CodePudding user response：

When you call the method its instantiating a eloquent instance in which you can extend it to a query which will give you a Category model

example (this might not be the most appropriate example)

$trip = Trip::findOrFail(1);

return $trip->category()->where('category_name', 'something')->first();

And the latter returns a collection.