Walker_CategoryDropdown
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概述
Walker_CategoryDropdown 是 WordPress 核心类，用于生成分类的 HTML 下拉列表。它继承自 Walker 类，专门处理分类树结构，通过 start_el 方法构建下拉选项。
关键要点
- 继承自 Walker 类，用于处理分类（category）树结构，生成下拉列表。
- 定义了 $tree_type 为 'category' 和 $db_fields 数组，指定数据库字段映射。
- 核心方法 start_el 负责输出每个下拉选项，支持参数如 selected、show_count 和 value_field。
- 方法内部使用过滤器 list_cats 修改分类名称，并处理选项选中状态和计数显示。
代码示例
public function start_el( &$output, $data_object, $depth = 0, $args = array(), $current_object_id = 0 ) {
$category = $data_object;
$pad = str_repeat( ' ', $depth * 3 );
$cat_name = apply_filters( 'list_cats', $category->name, $category );
if ( isset( $args['value_field'] ) && isset( $category->{$args['value_field']} ) ) {
$value_field = $args['value_field'];
} else {
$value_field = 'term_id';
}
$output .= " {$value_field} ) . '"";
if ( (string) $category->{$value_field} === (string) $args['selected'] ) {
$output .= ' selected="selected"';
}
$output .= '>';
$output .= $pad . $cat_name;
if ( $args['show_count'] ) {
$output .= ' (' . number_format_i18n( $category->count ) . ')';
}
$output .= "n";
}注意事项
- 从 WordPress 5.9.0 开始，start_el 方法的参数 $category 和 $id 更名为 $data_object 和 $current_object_id，以支持 PHP 8 命名参数。
- 使用 $value_field 参数可自定义选项值字段，默认为 term_id。
- 通过 $args['selected'] 设置选中项，需进行字符串类型转换以避免误匹配。
- 相关类 Walker 位于 wp-includes/class-wp-walker.php，用于显示树状结构。
原文内容
Core class used to create an HTML dropdown list of Categories.
Description
See also
Methods
| Name | Description |
|---|---|
| Walker_CategoryDropdown::start_el | Starts the element output. |
Source
class Walker_CategoryDropdown extends Walker {
/**
* What the class handles.
*
* @since 2.1.0
* @var string
*
* @see Walker::$tree_type
*/
public $tree_type = 'category';
/**
* Database fields to use.
*
* @since 2.1.0
* @todo Decouple this
* @var string[]
*
* @see Walker::$db_fields
*/
public $db_fields = array(
'parent' => 'parent',
'id' => 'term_id',
);
/**
* Starts the element output.
*
* @since 2.1.0
* @since 5.9.0 Renamed `$category` to `$data_object` and `$id` to `$current_object_id`
* to match parent class for PHP 8 named parameter support.
*
* @see Walker::start_el()
*
* @param string $output Used to append additional content (passed by reference).
* @param WP_Term $data_object Category data object.
* @param int $depth Depth of category. Used for padding.
* @param array $args Uses 'selected', 'show_count', and 'value_field' keys, if they exist.
* See wp_dropdown_categories().
* @param int $current_object_id Optional. ID of the current category. Default 0.
*/
public function start_el( &$output, $data_object, $depth = 0, $args = array(), $current_object_id = 0 ) {
// Restores the more descriptive, specific name for use within this method.
$category = $data_object;
$pad = str_repeat( ' ', $depth * 3 );
/** This filter is documented in wp-includes/category-template.php */
$cat_name = apply_filters( 'list_cats', $category->name, $category );
if ( isset( $args['value_field'] ) && isset( $category->{$args['value_field']} ) ) {
$value_field = $args['value_field'];
} else {
$value_field = 'term_id';
}
$output .= "t<option class="level-$depth" value="" . esc_attr( $category->{$value_field} ) . '"';
// Type-juggling causes false matches, so we force everything to a string.
if ( (string) $category->{$value_field} === (string) $args['selected'] ) {
$output .= ' selected="selected"';
}
$output .= '>';
$output .= $pad . $cat_name;
if ( $args['show_count'] ) {
$output .= ' (' . number_format_i18n( $category->count ) . ')';
}
$output .= "</option>n";
}
}
Changelog
| Version | Description |
|---|---|
| 2.1.0 | Introduced. |