Fill Gravity Forms Choices From Your Posts

$wpide_gf_populate = function ( $form ) {
    foreach ( $form['fields'] as $field ) {
        if ( ! in_array( $field->type, array( 'select', 'radio', 'checkbox', 'multiselect' ), true ) || ! preg_match( '/\bpopulate-([a-z0-9_-]+)\b/', (string) $field->cssClass, $m ) ) {
            continue;
        }

        $type = 'posts' === $m[1] ? 'post' : $m[1];
        if ( ! post_type_exists( $type ) ) {
            continue;
        }

        $cache   = 'wpide_gf_choices_' . $type;
        $choices = get_transient( $cache );

        if ( false === $choices ) {
            $choices = array();
            $ids     = get_posts( array( 'post_type' => $type, 'post_status' => 'publish', 'numberposts' => 200, 'orderby' => 'title', 'order' => 'ASC', 'fields' => 'ids', 'no_found_rows' => true ) );
            foreach ( $ids as $id ) {
                $title     = wp_strip_all_tags( get_the_title( $id ) );
                $choices[] = array( 'text' => $title, 'value' => $title );
            }
            set_transient( $cache, $choices, HOUR_IN_SECONDS );
        }

        $field->choices = $choices;

        if ( 'checkbox' === $field->type ) {
            $inputs = array();
            foreach ( $choices as $i => $choice ) {
                $inputs[] = array( 'id' => $field->id . '.' . ( $i + 1 + (int) floor( $i / 9 ) ), 'label' => $choice['text'] );
            }
            $field->inputs = $inputs;
        }
    }

    return $form;
};

add_filter( 'gform_pre_render', $wpide_gf_populate );
add_filter( 'gform_pre_validation', $wpide_gf_populate );
add_filter( 'gform_pre_submission_filter', $wpide_gf_populate );
add_filter( 'gform_admin_pre_render', $wpide_gf_populate );

add_action( 'save_post', function ( $post_id, $post ) {
    delete_transient( 'wpide_gf_choices_' . $post->post_type );
}, 10, 2 );