Delete Data product

I have 3 tables

• product

id,name,price

• sale

id, product_id,sale_price

• purchase

id, product_id,purchase_price

how to delete a product, if the data sale and purchase 0 then the product will be deleted but if the data is not 0 the product will not deleted

I use this:

 public function destroy($id)
    {
        $products = Product::find($id);
        if (count($products->sale_detail) == 0 && count($products->purchase_detail) == 0) {
            $products->delete;
            return redirect($this->title)->with('success', 'Procuct Deleted!!');
        } else {
            return redirect($this->title)->with('error', 'Something Went Wrong!!');
        }
    }

but it doesn't work

model product:

  public function purchase_detail()
    {
        return $this->hasMany('App\Model\PurchaseDetail');
    }

 public function sale_detail()
    {
        return $this->hasMany('App\Model\SaleDetail');
    }

model sale:

 public function product()
    {
        return $this->belongsTo(App\Model\Product);
    }

model purchase:

 public function product()
    {
        return $this->belongsTo(App\Model\Product);
    }