Yii don't understand how to log a message

Question

I followed this tutorial but still I go to the webpage refresh, then go to the file and still I can't find the log message I sent I wrote the following line in a controller:

Yii::log("Index Checkout",CLogger::LEVEL_ERROR);

And My configurations:

'log' => array(
            'class' => 'CLogRouter',
            'routes' => array(
                array(
                    'logFile'=>'trace.log',
                    'class' => 'CFileLogRoute',
                    'levels' => 'error,info, warning',
                ),
            // uncomment the following to show log messages on web pages
            /*
              array(
              'class'=>'CWebLogRoute',
              ),
             */
            ),

Answer 1

Right way to write to log is:

Yii::log($message, $level, $category);

But point is that $category should not be empty.

Example above works becouse message is written in category then category is not empty, but it writes empty message. It writes category so it looks like message.. but it isn't.