protected function _after_find(&$result, $options)
 {
     $picture = get_slide_cover($result['cover_id'], 'url');
     if (empty($picture)) {
         $result['slide_picture'] = "http://image.lol.zhanglubao.com/default/default-video.jpg";
     } else {
         $result['slide_picture'] = $picture;
     }
 }
					<div class="form-group">
						<label for="articleIntro" class="col-lg-2 control-label">广告图片</label>
						<div class="col-lg-10">
							<input type="file" id="upload_picture"> <input id="cover_id"
								type="hidden" name="cover_id" value="<?php 
echo $info['cover_id'];
?>
" />
							<div class="upload-img-box">
								<?php 
if (!empty($info['cover_id'])) {
    ?>
<div class="upload-pre-item">
									<img src="<?php 
    echo get_slide_cover($info['cover_id'], 'url');
    ?>
" />
								</div><?php 
}
?>
							</div>
						</div>
					</div>



					<div class="form-group">
						<div class="col-lg-offset-2 col-lg-10">
						<input type="hidden" name="id" value="<?php 
echo $info["id"];