Is it possible to modify a WP_Query object to add a tax_query?
That is — I’m able to add a tax_query when instantiating a WP_Query object
$q = new WP_Query(array(
'post_type' => 'post',
'tax_query' => array(
array(
'taxonomy' => 'post_format',
'field' => 'slug',
'terms' => array(
'post-format-link',
),
'operator' => 'IN'
)
)
));
The above query only returns posts with a link format.
However, if I have an already instantiated WP_Query object, I’m not able to set a tax_query. If I try it like this
$q = new WP_Query(['post_type'=>'post']);
$q->set('tax_query', array(
array(
'taxonomy' => 'post_format',
'field' => 'slug',
'terms' => array(
'post-format-link',
),
'operator' => 'IN'
)
));
My query returns all post types, not just link posts.
Is this possible to do? If so, am I using set wrong, or do tax queries need to be set differently?
If it helps, the larger context is I’m trying to change a query object in the pre_get_posts action-hook. I’ve been able to use the pre_get_posts hook to add a category filter to a query
add_action('pre_get_posts', function($query) {
if(!$query->is_main_query() || is_admin() || !is_front_page()) {
return;
}
$term = get_category_by_slug('my-slug');
if(!$term || !is_numeric($term->term_id)) {
return;
}
$query->set('category__not_in', $term->term_id);
});
With the above in place my front page omits posts with the my-slug category.
However, if I try a similar thing with a tax_query, the front page is not restricted to link posts. The following
add_action('pre_get_posts', function($query) {
if(!$query->is_main_query() || is_admin() || !is_front_page()) {
return;
}
// per an answer below, I've tried things both with and without
// this next line and have not had luck in getting my tax_query
// to apply to the WP_Query
// $tax_query = $query->get( 'tax_query', [] );
$query->set('tax_query',
array(
'taxonomy' => 'post_format',
'field' => 'slug',
'terms' => array(
'post-format-link',
),
'operator' => 'IN'
)
);
});
has no effect on the global query for the front page.
