Laravel relationship based on custom attribute not working both directions

问题

Models Product and Category.

Product model has this custom attribute: getCategoryIdAttribute(). because the way to get category id is a bit complex.

With that attribute I can define the relationship (Product -> Category):

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

This relationship works fine!

But now on the Category model:

public function products()
{
    return $this->hasMany(Product::class, 'category_id', 'id');
}

If I use this relationship it fails on SQL.

Example on tinker:

Product::first()->category; // Works!
Category::first()->products; // Undefined column: 7 ERROR:  column products.category_id does not exist

Why when I use the relationship Product -> Category works but Category -> Products doesn't?

来源：https://stackoverflow.com/questions/64483032/laravel-relationship-based-on-custom-attribute-not-working-both-directions