Access model properties from relationship function - php

Question

I had an accessor set on my Eloquent model that worked fine, but the associated database query was getting run once for every instance of the model I created. On my index page this meant 5 dozen queries.
<?php
class Thingy extends Model {
protected $appends = ["parentType"];
public function getParentTypeAttribute($value) {
return self::where("type"=>$this->type, "parent"=>1)->value("name");
}
}
class ThingyController extends Controller {
public function index() {
$thingys = Thingy::all();
return view("things.index", compact("thingys"));
}
}
To explain briefly: there are two classes of "thingy" in the same database table, the class being indicated by a boolean value named "parent." I want to get the name of the parent when I access the child. I know this should be two tables but it's not.
I wanted to reduce the number of database reads, so I tried changing it to a relationship instead. I figured this way I could take advantage of eager loading.
<?php
class Thingy extends Model {
public function parent() {
return $this->hasOne("Thingy", "id")->where("type"=>$this->type, "parent"=>1);
}
}
class ThingyController extends Controller {
public function index() {
$thingys = Thingy::with(["parent"]);
return view("things.index", compact("thingys"));
}
}
The problem is that within the relationship method, $this is an empty instance of the model, unlike in the accessor, so $this->type is null.
Is there a way to access properties of the model I'm working with from within a relationship method?

Answer 1

Figured that out. Since I'm essentially doing a self-join on the same table, I can specify the "local" and "foreign" ID columns as the column I'm trying to match:
public function parent() {
return $this->hasOne("Thingy", "type", "type")->where("parent"=>1);
}
I guess the key concept was to remember that I'm defining a relationship between two instances of the model, which is independent of the particular instances I'm dealing with.