code: public function addClassArgument($name, $class, $required = true)
  	{
  		return $this->addArgument(new ClassArgument($this->argumentPosition++, $name, $class, $required));
  	}
docs: Add a class argument to the factory definition.
  
  @param string  $name
  @param string  $class
  @param boolean $required Optional - defaults to true