<?php if ( have_posts() ) : ?>
 <?php twentyeleven_content_nav( 'nav-above' ); ?>
 <?php /* Start the Loop 在循环中使用以调用不同类型的文章 */ ?>
 <?php while ( have_posts() ) : the_post(); ?>
 <?php get_template_part( 'content', get_post_format() ); ?>
 <?php endwhile; ?>
............................
<?php endif; ?>

<?php get_template_part( $slug, $name ) ?>

<?php get_template_part( 'loop', 'index' ); ?>

<?php get_template_part( 'nav' );      // Navigation bar (nav.php) ?>
<?php get_template_part( 'nav', '2' );   // Navigation bar #2 (nav-2.php) ?>
<?php get_template_part( 'nav', 'single' ); // Navigation bar to use in single pages (nav-single.php) ?>

 function get_template_part( $slug, $name = null ) {
//$tag = "get_template_part_{$slug}" 
//也就是，get_template_part_+你当时设置的$slug值
 do_action( "get_template_part_{$slug}", $slug, $name );
 $templates = array();
 if ( isset($name) )
  $templates[] = "{$slug}-{$name}.php";
  $templates[] = "{$slug}.php";
  locate_template($templates, true, false);
}

//复习一下get_template_part($slug, $name)的用法，
//如果你在主题里这样
get_template_part( 'index' , 'photo');
//那么 WP 会去找主题根目录下 index-photo.php 文件
 
//那么我们想挂一个函数的话就得像如下
function addFunction ($slug, $name){
echo $slug;
}
add_action("get_template_part_index","addFunction",10,2);