How to add an additional attribute to the model?

Question

Laravel

As an example, I give an elementary situation: it is necessary in the simplest form to calculate the difference between two fields of the table and display the result in a separate manual / virtual / non-existent attribute.
Something like this:

public function getSourceIncomingAttribute($item) {
    $this->attributes['total_profit'] = $this->attributes['source_incoming'] - $this->attributes['source_selfcost'];
}

But how should it really be or is there even a normal solution without crutches?! :)

Answer 1

RTFM
protected $appends = array('total_profit');

Answer 2

laravel.com/docs/5.1/eloquent-mutators