php - Add a custom attribute to a Laravel / Eloquent model on load?

Question

I'd like to be able to add a custom attribute/property to an Laravel/Eloquent model when it is loaded, similar to how that might be achieved with RedBean's $model->open() method.

For instance, at the moment, in my controller I have:

public function index()
{
    $sessions = EventSession::all();
    foreach ($sessions as $i => $session) {
        $sessions[$i]->available = $session->getAvailability();
    }
    return $sessions;
}

It would be nice to be able to omit the loop and have the 'available' attribute already set and populated.

I've tried using some of the model events described in the documentation to attach this property when the object loads, but without success so far.

Notes:

• 'available' is not a field in the underlying table.
• $sessions is being returned as a JSON object as part of an API, and therefore calling something like $session->available() in a template isn't an option

Answer 1

The problem is caused by the fact that the Model's toArray() method ignores any accessors which do not directly relate to a column in the underlying table.

As Taylor Otwell mentioned here, "This is intentional and for performance reasons." However there is an easy way to achieve this:

class EventSession extends Eloquent {

    protected $table = 'sessions';
    protected $appends = array('availability');

    public function getAvailabilityAttribute()
    {
        return $this->calculateAvailability();  
    }
}

Any attributes listed in the $appends property will automatically be included in the array or JSON form of the model, provided that you've added the appropriate accessor.

Old answer (for Laravel versions < 4.08):

The best solution that I've found is to override the toArray() method and either explicity set the attribute:

class Book extends Eloquent {

    protected $table = 'books';

    public function toArray()
    {
        $array = parent::toArray();
        $array['upper'] = $this->upper;
        return $array;
    }

    public function getUpperAttribute()
    {
        return strtoupper($this->title);    
    }

}

or, if you have lots of custom accessors, loop through them all and apply them:

class Book extends Eloquent {

    protected $table = 'books';

    public function toArray()
    {
        $array = parent::toArray();
        foreach ($this->getMutatedAttributes() as $key)
        {
            if ( ! array_key_exists($key, $array)) {
                $array[$key] = $this->{$key};   
            }
        }
        return $array;
    }

    public function getUpperAttribute()
    {
        return strtoupper($this->title);    
    }

}