Find Records Based on Distant belongsToMany > belongsTo Relationship - laravel

Question

I'm attempting to display a product page with a list of assets that match a specific asset type. For example, for product "Acme Cream", there are two assets: nutrition-facts.pdf (of type Document) and marketing-video.mp4 (of type Video). On the product page, I'd like to display the first asset that match the 'Video' asset type (if any exist).
I have the following relationships:
The Product model includes a DB column asset_id.
class Product extends Model
{
/**
* The assets that belong to the product.
*/
public function assets()
{
return $this->belongsToMany('App\Asset', 'product_asset');
}
}
The Asset model includes DB columns id and asset_type_id.
class Asset extends Model
{
/**
* Get the asset type that owns the asset.
*/
public function asset_type()
{
return $this->belongsTo('App\AssetType');
}
/**
* The products that belong to the asset.
*/
public function products()
{
return $this->belongsToMany('App\Product', 'product_asset');
}
}
The AssetType model has two DB columns id and name.
class AssetType extends Model
{
/**
* A asset type can have many assets
*/
public function assets()
{
return $this->hasMany('App\Asset');
}
}
How can I efficiently fetch the one product asset by filtering on asset_type? Keep in mind, I've already queried the DB using Product::find(id) and passed that data into the view. Will this require another query (eager loading might help with that). I know I could use a foreach loop, but it seems to me there's gotta be a nicer, more 'eloquent' way.
I'm trying to use it in this situation (pseudo code) on the product detail page (show.blade.php):
if assets matching type 'Video', then display first in this div. Else, don't display the div.
It seems like it should be a simple line:
$product->assets()->asset_type()->where('name', '=', 'Video')->first()
The closest I've come so far to this is this ugly looking thing:
>>> $product = App\Product::with(['assets'])->find(1)
>>> $product->assets()->with(['asset_type' => function ($query) { $query->where('name', '=', 'Video'); }])->get()
However, it still returns all assets, except the "asset_type" attribute is null for those that don't match. Adding ->whereNotNull('asset_type')->get() only results in an error that asset_type column cannot be found.
Also, this sounds like a chance to use the "Has Many Through" relationship, but I'm unclear how to set this up.
Any help is greatly appreciated! Thanks.

Answer 1

You need to eager-load your relationship with filtering:
Assuming you fetch the relationship with your product info
$typeName = 'Video';
$product = App\Product::with([
'asset' => function($query) use($typeName) {
//Filter asset by type
//See: https://laravel.com/docs/5.6/eloquent-relationships#constraining-eager-loads
return $query->whereHas('asset_type',function($query) use($typeName) {
//Filter where the type's name equals..
//Each query is relative to its scope, in this case the 'type' relationship which refers to your 'type' Model
return $query->where('name','=',$typeName);
});
},
//Nested relationship loading: https://laravel.com/docs/5.6/eloquent-relationships#querying-relations
'assets.asset_type'
])
->find(1);
$assets = $product->assets;
Assuming you fetch only the assets
$productId = 1;
$typeName = 'Video';
//Returns a collection of eloquent models
$assets = Asset::whereHas('product',function($query) use ($productId) {
//Filter product by its id
return $query->where('id','=',$productId);
})
->whereHas('asset_type',function($query) use ($typeName) {
//Filter type by its name
return $query->where('name','=',$typeName);
})
->get();