How to set a global var for all displayed post IDs like Genesis

The Genesis theme framework sets a global var $_genesis_displayed_ids which is an array with all the displayed post IDs.

I needed this kind of data for a WordPress installation without Genesis. We have the function the_post() but we also have the action hook the_post, which helped me to retrieve the data.
This is the snippet that makes use of this action hook to retrieve all the IDs in a global var.

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add_action( 'the_post', 'set_displayed_items' );
 
public static function set_displayed_items( $post_object ) {
 
 global $_displayed_ids;
 $_displayed_ids[] = $post_object->ID;
 
}