src/Caller.php
public function onHalt(string $eventClass = null)
    {
        if ($eventClass === null) {
            return $this->haltEvent;
        } else {
            $this->haltEvent = $eventClass;
            return $this;
        }
    }
public function onHalt(string $eventClass = null)
    {
        if ($eventClass === null) {
            return $this->haltEvent;
        } else {
            $this->haltEvent = $eventClass;
            return $this;
        }
    }
$haltEvent setter and getter. Must be a class name that resolves to a dispatchable event.

@param string|null $eventClass
@return $this|string