Laravel define a default key with value on Model - php

Question

In my Laravel 8 project I have a model called Campaign, my front-end though is build in Vue JS so needs to have some keys on a Campaign for contextual purposes, such as opening and closing a dropdown menu when looping over the elements, a database column isn't nessecery for this.
I'd like to add some default key/value pairs to my Campaign model, for example: dropdown_is_open and should have a default value of false.
I came across the default attributes for a model and tried adding this but cannot see my new key on the object, what am I missing?
<?php
namespace App\Models;
use Illuminate\Database\Eloquent\Factories\HasFactory;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\SoftDeletes;
class Campaign extends Model
{
use HasFactory, SoftDeletes;
/**
* Indicates if the model's ID is auto-incrementing.
*
* #var bool
*/
public $incrementing = false;
/**
* The table associated with the model.
*
* #var string
*/
protected $table = 'campaigns';
/**
* The attributes that are mass assignable.
*
* #var array<int, string>
*/
protected $fillable = [
'campaign',
'template'
];
/**
* The model's default values for attributes.
*
* #var array
*/
protected $attributes = [
'dropdown_is_open' => false
];
}
Index function in controller:
/**
* Display a listing of the resource.
*
* #return \Illuminate\Http\Response
*/
public function index()
{
$campaigns = Campaign::where('user_id', Auth::id())
->orderBy('created_at', 'desc')
->get();
if (!$campaigns) {
return response()->json([
'message' => "You have no campaigns"
], 404);
}
return response()->json([
'campaigns' => $campaigns
], 200);
}
I expect to see:
{
campaign: 'my campaign',
template: '',
dropdown_is_open: false <-- my key
}
Previously I was doing a foreach in my index function and adding the contextual keys on each item, but this would only show for the index function and I'd have to add it everywhere.

Answer 1

I hope something like below helps.
Change it from my_custom_field to dropdown_is_open key (and from getMyCustomFieldAttribute to getDropdownIsOpenAttribute method-name).
Custom attribute (or Accessor)
<?php
namespace App\Models;
use Illuminate\Database\Eloquent\Model;
class User extends Model {
protected $appends = ['my_custom_field'];
public function getMyCustomFieldAttribute()
{
return false;
}
}
The $appends in above is required only,
to ensure that my_custom_field is preset/cached, and even sent as JSON-Response.