BuddyPress.org

1) No, you don’t have to use BP_Component, but if you can, you probably should. It’s so much easier than trying to figure out which hooks to use. If you don’t need a particular method for your plugin (because it doesn’t have any navigation elements, for instance), just don’t include that method.

2) There seems to be a bug in the way the includes() method works for plugins. For the moment, I recommend that you include your files manually.

3) You need to call the $bp global before instantiating your class.
`global $bp;
$bp->query_subscribe = new BP_Query_Subscribe();`

The reason why you’re not seeing the callback when you print is because the component class isn’t fully initialized at the time when you’re adding yourself to $bp. Try this:

`function bp_query_subscribe_init(){
global $bp;

if ( !isset( $bp->query_subscribe ) ){
$bp->query_subscribe = new BP_Query_Subscribe();
}
}
add_action( ‘bp_loaded’, ‘bp_query_subscribe_init’ );

function bp_query_test() {
global $bp;
var_dump( $bp->query_subscribe );
}
add_action( ‘bp_init’, ‘bp_query_test’, 999 );`

As for includes, you will need to do your own manual include() for now. Don’t use BP_Component::includes().

Just to be clear, the notification function is a callback – you shouldn’t be calling it directly. Use bp_core_add_notification(). See bp-groups-notifications.php for an example of how it works.