Chain whereHas to traverse through a self-referencing model - laravel

Question

Using Laravel 5.4....
Imagine I have the following models:
App\Location
This has a self referencing hierarchy, and has the following data
UK
|---North West
| |----Liverpool
| |----Manchester
|---North East
|----Newcastle
|----Sunderland
In this model I have a self relation
public function parent()
{
return $this->belongsTo('App\Location', 'location_id');
}
and a recursive relation...
public function parentRecursive()
{
return $this->parent()->with('parentRecursive');
}
App\Shop
The shop model has a 'location' relation.
public function location()
{
return $this->belongsTo('App\Location', 'location_id');
}
What I want to do is to get all of the shops within a category. So if I have a shop called "ACME" that is related to "Liverpool", I can easily get it by sending the ID for "Liverpool" (as $value) in the following condition....
->whereHas('location', function($q) use ($value) {
$q->where('id', $value);
})
But technically, this shop is also in "North West" and in "UK".
So if I send the ID for the UK Location to that query, it will not return the ACME shop as it is not directly related to North West or UK ID.
I can get it working by sending the UK id ($value) to this...
$this->builder->whereHas('location', function($q) use ($value) {
$q->where('id', $value);
})->orWhereHas('location.parent', function($q) use ($value) {
$q->where('id', $value);
})->orWhereHas('location.parent.parent', function($q) use ($value) {
$q->where('id', $value);
});
So is there a better way to write the above which is ugly and would only work for a finite number of 'jumps' in the relation tree? I need it to traverse all of the locations until it reaches the top of the tree.

Answer 1

I encountered the same problem. My solution is not that elegant, but it works without having to use a nested set model:
First, (if you haven't done yet) you may need to create an inverse of your existing recursive relation:
public function children() {
return $this->hasMany('App\Location', 'location_id');
}
public function childrenRecursive() {
return $this->children()->with('childrenRecursive');
}
Next, you need to create a recursive function to get the max depth
public function getDepth($location) {
$depth = 0;
foreach ($location->children as $child) {
$d = $this->getDepth($child);
if ($d > $depth) {
$depth = $d;
}
}
return 1 + $depth;
}
Then, you can use the depth to chain your query with multiple orWhereHas clause
$whereHas = 'location';
$query = Shop::whereHas($whereHas, function ($q) use ($value) {
$q->where('id', $value);
});
for ($d = 1; $depth > $d; $d++) {
$whereHas = $whereHas . '.parent';
$query->orWhereHas($whereHas, function ($q) use ($value) {
$q->where('id', $value);
});
}