Has many through self referencing in laravel returns empty set

Question

I'm using laravel v8 and i have a products table to hold a product data, the product will have a child product and i'm connecting it using product_relations table.

products table:

id	name
1	PC
2	Mouse
3	VGA

product_relations table

id	parent_product_id	child_product_id
1	1	2
2	1	3

I want to retrieve the child product model using the parent product model, to achieve this I'm trying to use hasManyThrough function in class model like this;

class Product extends Model{
    protected $primaryKey = 'id';
    protected $table = 'products';
    public function childs(){
        return $this->hasManyThrough(self::class, ProductRelation::class, 'child_product_id', 'id');
    }
}

class ProductRelation extends Model{
    protected $primaryKey = 'id';
    protected $table = 'product_relations'; 
}

then i tried to retrieve it like this:

$childs = Product::find(1)->childs()->get();

but it returns an empty set of product model

I take it there is only 2 levels to the relationships i.e. `parent` > `child` and not `parent` > `child` > `grandchild` etc.? — Rwd, Oct 01 '21 at 08:23
Why not just have a parent_id and a one-to-many relationship? Side note: I would change `childs` to `children` — Gert B., Oct 01 '21 at 09:31
@GertB. sadly i don't have the authority to change the db structure — gaby, Oct 01 '21 at 09:41
In that case you are looking for the `belongsToMany` with `product_relations` as the pivot table — Gert B., Oct 01 '21 at 09:44

score 2 · Answer 1 · answered Oct 01 '21 at 08:28

2

1- this kind of relation is not necessary. because parent product and children products have one-to-many relations not many-to-many.

2- hasManyThrough get destination class address not self::class.(like: ChildProduct::class)

answered Oct 01 '21 at 08:28

Hamid Moladoust

56
4

score 1 · Answer 2 · answered Oct 01 '21 at 09:48

1

You are looking for a many-to-many with a pivot table:

public function childs(){
    return $this->belongsToMany(self::class, 'product_relations', 'parent_product_id', 'child_product_id');

    }

answered Oct 01 '21 at 09:48

Gert B.

2,282
18
21

Has many through self referencing in laravel returns empty set

2 Answers2

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