Problem ID to exclude specific posts from category

Question

I'm trying to exclude specific posts from category/archive with these functions:

function exclude_single_posts_cat($query) {
      if ( is_admin() || ! $query->is_main_query() )
        return;
     if ($query->is_archive() ) {
          $query->set('post__not_in', array('1','2','3'));}} 
          //I've also tried** ('-1','-2','-3') or without quotes
      }
}
add_action('pre_get_posts', 'exclude_single_posts_cat',);

Or:

function exclude_single_posts_cat($query) {
     if ($query->is_category() AND $query->is_main_query()) {
        $query->set('post__not_in', array('1','2','3'));}} 
       //I've also tried** ('-1','-2','-3') or without quotes.
     }
}
add_action('pre_get_posts', 'exclude_single_posts_cat');

But something happens that I can't explain, that is, there disappear posts that don't correspond to the specified ID (following the example, the hidden posts may be '4', '5', '6' ). Could someone tell me why it happens and where I'm wrong, please?

Thank you in advance.

Answer 1

Try this:

function exclude_single_posts_cat($query) {
    if ( is_admin() || ! $query->is_main_query() )
        return;
    if ( $query->is_archive() ) {
        $query->set('post__not_in', array('1','2','3'));
    }
}
add_action('pre_get_posts', 'exclude_single_posts_cat');

Issue: The issue in your first approach is you have added extra curly brackets and comma.