[TYPO3-mvc] getX returns a boolean, isX returns null

[Stephen Bungert]

I have the following method in one of my models:



	/**
	 * Returns classes for the item to aid css styling (based on the values 
of certain properties)
	 *
	 * @return string Classes for the item
	 */
	public function getClasses() {
		$classes = '';
		
		if ($this->getSoldout()) {
			$classes .= ' soldout';
			// using the "get" methods, returns a boolean value
			echo "soldout " . gettype($this->getSoldout());
		} else {
			echo "not soldout " . gettype($this->getSoldout());
		}
		
		if ($this->isPremier()) {
			$classes .= ' premier';
			// using the "is" methods, returns null even if a get method would 
return true
			echo "premier " . gettype($this->isPremier());
		} else {
			echo "not premier " . gettype($this->isPremier());
		}
		
		if ($this->isCancelled() == true) {
			$classes .= ' cancelled';
		}
		
		return $classes;
	}

I find that using '$this->getSoldout()' returns true or false (premier, 
soldout and cancelled are all boolean values), whereas 
'$this->isSoldout()' retuns null whatever the actual property is set to.

isSoldout() is defined for me by the kickstarter, am I supposed to test 
in the function what the return value is instead of just returning what 
is getSoldout() returns? isSoldout just calls getSoldout, so why does it 
return null?