Laravel 4 - 创建工匠命令

This is my first attempt to create an artisan command, which should be responsible for executing another php function. All I did so far is to create the command with: php artisan command:make PutItemsBackInStock and created the skeleton for the command. Also, I added the command in app/start/artisan.php so Laravel knows about it.

Then in PutItemsBackInStock file I declared a private function:

private function updateItemQty() { ... }

And under the public function fire() I tried to call it:

$this->updateItemQty();

This is probably not the right way to do it, while I got that error:

[RuntimeException] Not enough arguments.

Then I removed the blocks for the protected functions getArguments() and getOptions() which removed that error but still the function is not firing.

The question is: How can I get an artisan command to execute another function?