Laravel中多级查询

Question

I have a Category / Products / Users I need to get all Categories of All Products for a specific user. I was able to make selecting a product for a specific User but I couldn't tell how to get all the categories of these products.

Products and Users relationship is ManyToMany. The relationship between product belongsTo Category and Category hasMany Products

Here is what I made:

$products = Product::byUser(auth()->id())->get();

public function scopeByUser(Builder $query)
{
    return $query->whereHas('users', function ($q) {
        $q->where('id', auth()->id());
    });
}

But I couldn't make it in a way to have:

$products = Category::productsByUser(auth()->id());

So that I can get all the categories and all the products of the loggedIn user.

Thank you,

Answer 1

You can either load the categories with the products in a single query to get a list of the products associated to a user. Or you can create a scope filter on the category model to return a list of categories associated with products that are associated with the user:

Load categories with() products:

Eager Loading Relationships

$products = Product::with('categories')->byUser(auth()->user()->id)->get();

This will return a collection of products which already have the related categories loaded so you can call $products->first()->categories()->get() to return a list of the categories for that product.

Use a scope filter on the Category Model to list categories only:

Query Scopes

public function scopeByUser(Builder $query, $user_id)
{
    return $query->whereHas('products', function ($q) use($user_id) {
        $q->whereHas('user', function ($q) use($user_id){
            $q->where('id', $user_id);
        }
    });
}

Then you can run Category::byUser(auth()->user()->id)->get(); to return a collection of categories which are associated to products which are associated to user id given.

UPDATE: Conditional Eager Loading with Scope filter

You still want to user eager loading with a condition to load all products which are associated to the user and then apply the above scope filter to limit the categories returned to only be those associated to the user:

$user_id = auth()->user()->id;
$categories = Category::with(['products'=> function($q) use($user_id){
    $q->whereHas('user',function($q) use($user_id){
        $q->where('id',$user_id);
    });
}])->byUser($user_id)->get()

This will return a collection of Categories which are associated to products which are associated to the provided user id and will eager load products for the category if those products are associated with the user id provided.