Prevent Posts in a Category From Displaying in WordPress’ RSS Feed

I recently posted a snippet which prevented posts in a given category from displaying in WordPress' main loop.  I even went on to create my first WordPress plugin to accomplish the task via the WordPress control panel.  The one task those snippets doesn't complete is preventing posts from going into RSS feeds.  Here's how you can prevent posts in a category from displaying in the RSS feed!

The PHP

The category check is done the same way the loop check was done:

function postsFilter($query) {
    // Prevent from RSS feed
    if($query->is_feed()) {
    	// No posts in category #11 may go into the feed
    	$query->set('cat', '-11');
    }
}
add_action('pre_get_posts', 'postsFilter');

A pre_get_posts filter is added to check for the is_feed() return value.  If the value is true, we add the condition to remove the category form the final query.  I have added this functionality to the WordPress plugin as well!