Query Laravel nested relationship [Laravel 6.x] - laravel

Question

I have a page in my Laravel app where I am fetching categories and eager loading events in that category. It works fine. What I want to do now is to fetch the categories alright but this time, fetch events based on a region/location selected by the user. These are the models I am working with;
1.Region Class
<?php
namespace App\Models;
use Illuminate\Database\Eloquent\Model;
class Region extends Model
{
/**
* Get events within region
*
* #return \Illuminate\Database\Eloquent\Relations\HasMany
*/
public function events()
{
return $this->hasMany(Event::class);
}
}
Category Class
<?php
namespace App\Models;
use Illuminate\Database\Eloquent\Model;
class Category extends Model
{
/**
* The attributes that are mass assignable.
*
* #var array
*/
protected $fillable = [
'category_name', 'description', 'type', 'slug'
];
/**
* Get all events that belong to a category
*
* #return Illuminate\Database\Eloquent\Relations\HasMany
*/
public function events()
{
return $this->hasMany(Event::class)->where('start_date', '>=', today())->orderBy('start_date', 'asc');
}
}
3.Event
<?php
namespace App\Models;
use Illuminate\Database\Eloquent\Model;
class Event extends Model
{
/**
* Get an event's category
*
* #return Illuminate\Database\Eloquent\Relations\BelongsTo;
*/
public function category()
{
return $this->belongsTo(Category::class);
}
/**
* Get region of event
*
* #return [type] [description]
*/
public function region()
{
return $this->belongsTo(Region::class);
}
}
This is the query that returns categories with events;
if (session()->has('region')) {
$region_name = session()->get('region');
$region = Region::where('region_name', $region_name)->firstOrFail();
$categories = Category::withCount('events')
->with('events')
->whereHas('events', function (Builder $query) use ($region) {
$query->where('region_id', $region->id);
})
->orderBy('events_count', 'desc')
->take(5)
->get();
}
Summary: I want to fetch top 5 categories with events in user's selected location.
Thanks in advance for your help.

Answer 1

Try this for the categories query:
$categories = Category::with(['events' => function ($query) use ($region) {
$query->where('region_id', $region->id);
}])->take(5)->get();
Check the documentation on restraining eager loads

Answer 2

Have you looked at the hasManyThrough relationship?
https://laravel.com/docs/5.8/eloquent-relationships#has-many-through
If you give your Region model many Categories through the Event class:
public function categories()
{
return $this->hasManyThrough('App\Category', 'App\Event');
}
You should be able to call:
$region->categories;
Which should return all the categories that have events for that region. You can then eager load the events in each category, sort by the number of events and take the first 5 before outputting to your view.
Alternative
An alternative would be to simply get all events where the region_id is the selected region and add a groupBy for category:
$eventsByCategory = Event::where('region_id', $selectedRegion)->groupBy('category_id);
Then once you have the events grouped by category you can sort by the count and take the top 5.
$eventsByCategory->sort()->take(5);
Side Note:
I'd be careful with your events relationship on the Category model. I think adding your where to the returned value will return an instance of Builder rather than Relation which means you may not be able to utilise some of the functionality of relationships.
I'd suggest looking at a scope on the Event model instead that you can apply globally or locally depending on how often you might want to get past events.