exchange/app/Models/Trading.php

<?php

namespace App\Models;

use Laravel\Scout\Searchable;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\Factories\HasFactory;

class Trading extends Model
{
    use \Backpack\CRUD\app\Models\Traits\CrudTrait;
    use HasFactory;

    protected $guarded = ['id'];
    protected $casts = [
        'price' => 'float',
        'total' => 'float',
        'amount' => 'float',
    ];
    protected $appends = ['total'];
    protected $with = ['category'];

    public function scopeLines($query)
    {
        return $query->where('is_line', true);
    }

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

    public function getTotalAttribute()
    {
        return round($this->price * $this->amount, 2);
    }
}