多个表的Laravel Eloquent关系问题

Question

In Laravel 5.5 I try to create a small application to manage products of a couple of sellers/stores.

Therefore, I have four different models like this:

Seller.php

class Attribute extends Model
{

    public function items()
    {

        return $this->belongsToMany(Item::class);
    }
}

Item.php

class Item extends Model
{

    public function seller()
    {

         return $this->belongsTo(Seller::class);
    }

    public function category()
    {

        return $this->belongsTo(Category::class);
    }

    public function attributes()
    {

        return $this->belongsToMany(Item::class);
    }
}

Category.php

class Category extends Model
{

    public function items()
    {

        return $this->hasMany(Item::class);
    }
}

Attribute.php

class Attribute extends Model
{

    public function items()
    {

        return $this->belongsToMany(Item::class);
    }
 }

For the many-to-many relation between Attributes & Items, I created a pivot table:

Schema::create('attribute_item', function (Blueprint $table) {
    $table->integer('attribute_id')->unsigned()->index();
    $table->foreign('attribute_id')->references('id')->on('attributes')->onDelete('cascade');
    $table->integer('item_id')->unsigned()->index();
    $table->foreign('item_id')->references('id')->on('items')->onDelete('cascade');
    $table->primary(['attribute_id', 'item_id']);
});

The goal of the entire application is to:

• fetch all items of a seller by category with attributes (for filtering or something)
• Fetch a specific item of an seller and get its attributes and category

I'm a little bit confused by Laravels relationhip methods and which one to use in that case.

May it is better to hasManyThrough or polymorphic relationhips?

I have to admit that I have a little logic problem here. Hopefully you can help me.

Thank you!

Answer 1

You can use whereHas method to find the nested relationship let's for example your first goal

fetch all items from a seller by category with attributes (for filtering or something)

You may write the following:

$items = Item::whereHas('seller.items', function ($query) {
        $query->whereHas('categories', function ($categories) {
            $categories->where('name', '=', 'Mens');
        })
        ->orWhereHas('attributes', function ($attributes) {
            $attriutes->where('size', '=', 'large');
        });
    })->get();

Find out more about this: https://laravel.com/docs/5.5/eloquent-relationships#querying-relationship-existence

This will give you the list of items if you want to get items with categories and attributes you can use with method to get the relational data:

$items = Item::whereHas('seller.items', function ($query) {
        $query->whereHas('categories', function ($caegories) {
            $categories->where('name', '=', 'Mens');
        })
        ->orWhereHas('attributes', function ($attributes) {
            $atributes->where('size', '=', 'large');
        });
    })
    ->with('categories', 'attributes')
    ->get();

Hope this guide you the problem which you are facing.