cannot get all posts after added rest_post_query

Question

I have add a rest_post_query like

add_filter( 'rest_books_query', function( $args ) {
    $args['meta_query'] = array(
        array(
            'key'   => 'title',
            'value' => esc_sql( $_GET['title'] ),
        )
    );
    return $args;

so query like wp-json/wp/v2/books?title=someTitle work, but I can't query all posts now like wp-json/wp/v2/books don't work anymore. How should I change it so it can query both? thanks

Answer 1

As I understand, you want to use the same API route to get All posts, or post by title. If so, you could simply do:

add_filter( 'rest_books_query', function( $args ) {
    if(isset($_GET['title'])){
      //better push to meta_query array in case there is other meta_query already here
      $args['meta_query'][] = [
            'key'   => 'title',
            'value' => esc_sql( $_GET['title'] ),
      ];
    }

    return $args;
});

If no title parameter provided, the meta_query will not be pushed to the query parameter array.

Note that you could also declare a new API route to do exactly what you require.