Dynamic comments for product create/update form fields

Question

I need to display message to admin in front of some custom product attribute, For example "Donation" fields which take decimals, I need to display message to admin that say's 20% is a minimum donation for this product.

This 20% will be different for other product, for some product it may be 15% or 10%. I have custom module that stores donation percentages to database.

My question is from database how Can I display message [like field comment] with dynamic message content.

Answer 1

You cannot set it from the database.
You will have to code for it.
You can make use of the after_element_html feature that the form builder offers.
So declaring a field like this:

$fieldset->addField('identifier_here', 'type_here',
    array(
        'name'      => 'name_here',
        'label'     => 'Label here',
        'required'  => true|false,
        'after_element_html'      => 'Some text after the element',
    )
)

will make your text Some text after the element appear after the element. It can be anything, even some html or javascript.
But there is a catch. The product add/edit form is not built using code as shown above. You cannot control each field. The fields are generated based on the attributes.
But you have the event adminhtml_catalog_product_edit_prepare_form that is dispatched for every tab that contains product attributes.
You can try to observe it like this (untested code):

public function prepareEditForm($observer) 
{
    $form = $observer->getEvent()->getForm();
    //let's say you want to add some message for the attribute with code `donation`
    $donationElement = $form->getElement('donation');
    if ($donationElement) {
         $message = ...determine the string to display....
         $donationElement->setAfterElementHtml($message);
    }
    return $this;
}

There is also an other approach. Each attribute supports a custom form renderer. This feature basically allows you to have the input be rendered using your own class and your own phtml file. This seams like a more complicated approach, but if you want to give it a try check this answer. It's for a different problem, but the approach is the same.