public function getSkylineAppDirectory(string $dirName) {
        $name = CC::get([], $dirName);
        if($name) {
            return $this->getSkylineAppDataDirectory() . "/$name";
        }
        return NULL;
    }
public function getSkylineAppDirectory(string $dirName) {
        $name = CC::get([], $dirName);
        if($name) {
            return $this->getSkylineAppDataDirectory() . "/$name";
        }
        return NULL;
    }
Returns the required Skyline CMS Application data sub directory

@param string $dirName
@return string
@see CompilerConfiguration::SKYLINE_DIR_* constants