I went through this tutorial: http://www.smashingmagazine.com/2014/03/13/tutorial-create-admin-manageable-magento-entity-brands/.
When accessing the post data, the author uses:
$this->getRequest()->getPost('brandData')
I am wondering how can we know there is a brandData key in the post data?
NOTE: I know I can see the available keys using the
var_dump($this->getRequest()->getPost())
But I want to know how to know it without manually print the whole post data.
The available fields all yield from html form elements whose values have been sent to the controller that then works with the post data.
So there probably is a code snippet similar to this one
<form method="post" action="/path/to/your/controllerAction">
<input type="text" name="brandData" value="Default value" />
</form>
on the page used to send data to your controller.