How to filter posts by category INSIDE the loop

Question

I'm trying to sort my posts like so:

CATEGORY 1 
- post title
- post title

CATEGORY 2
- post title
- post title 

I have no problem achieving this with a custom query:

<?php 
$args = array(
    'orderby' => 'name',
    'hide_emppty' => 1,
    'hierarchical' => false,
    'taxonomy' => 'course_category'
);
$categories = get_categories($args);
foreach ($categories as $category) : ?>

    <h3><?php echo $category->name; ?></h3>

    <?php $courses = new WP_Query( "post_type=courses&posts_per_page=-1&course_term=term-fall&course_category=" . $category->slug);  ?>
    <?php if ( $courses->have_posts() ) : while ( $courses->have_posts() ) : $courses->the_post(); ?>
        <?php the_title(); ?>
    <?php endwhile; endif; ?>

<?php endforeach; ?>

However, what I need to do is sort posts that come from a plugin-generated query (I have no (?) control over it) - so this needs to happen inside a normal if(have_posts()) : while (have_posts()) loop.

Is this even possible? The posts from this query are all of correct post type and course_term custom taxonomy, just need to get sorted by course_category taxonomy like above.

Thanks in advance for your help!

Answer 1

Got a quite radical solution :

function wpse_102497_modify_query_order( $query ) {
    if ( $query->is_main_query() ) {
      $query->set( 'orderby', 'title' );
    }
}
add_action( 'pre_get_posts', 'wpse_102497_modify_query_order' );

Hope this will help.