多态关联 laravel答案

【问题标题】：polymorphism association laravel多态关联 laravel
【发布时间】：2016-06-06 08:54:02
【问题描述】：

我正在尝试在 laravel 中实现多态关联，但它没有显示结果或错误。

餐桌：

CREATE TABLE IF NOT EXISTS `posts` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `content` varchar(255) NOT NULL,
  `created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ;


INSERT INTO `posts` (`id`, `name`, `content`, `created_at`, `updated_at`) VALUES
(1, 'php post', 'Php mysql javascript', '2016-06-06 07:16:49', '0000-00-00 00:00:00'),
(2, 'node', 'express node js', '2016-06-06 07:16:49', '0000-00-00 00:00:00');



CREATE TABLE IF NOT EXISTS `taggables` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `taggable_id` int(11) NOT NULL,
  `tag_id` int(11) NOT NULL,
  `taggable_type` varchar(255) NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=3 ;


INSERT INTO `taggables` (`id`, `taggable_id`, `tag_id`, `taggable_type`) VALUES
(1, 1, 1, 'Post'),
(2, 2, 2, 'Video');

CREATE TABLE IF NOT EXISTS `tags` (
  `id` int(11) NOT NULL AUTO_INCREMENT,
  `name` varchar(255) NOT NULL,
  `created_at` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
  `updated_at` timestamp NOT NULL DEFAULT '0000-00-00 00:00:00',
  PRIMARY KEY (`id`)
) ENGINE=InnoDB  DEFAULT CHARSET=latin1 AUTO_INCREMENT=7 ;

INSERT INTO `tags` (`id`, `name`, `created_at`, `updated_at`) VALUES
(1, 'ruby tag', '2016-06-06 07:20:00', '0000-00-00 00:00:00'),
(2, 'javascript tag', '2016-06-06 07:20:00', '0000-00-00 00:00:00'),
(3, 'rails tags', '2016-06-06 07:20:25', '0000-00-00 00:00:00');

另一个表是视频

型号

<?php
//Post.php
namespace App;
use Illuminate\Database\Eloquent\Model;

class Post extends Model {



    public function tags()
    {
        return $this->morphToMany('App\Tag', 'taggable');
    }
}

    <?php
namespace App;
use Illuminate\Database\Eloquent\Model;

class Tag extends Model {


    public function posts()
    {
        return $this->morphedByMany('App\Post', 'taggable');
    }

}



 <?php
namespace App;
use Illuminate\Database\Eloquent\Model;

class Tag extends Model {


    public function posts()
    {
        return $this->morphedByMany('App\Post', 'taggable');
    }

}

class PostController extends Controller {
    function index () {

        $id = 1;
        $a = Post::all();



        return view('Pages.index',compact('a'));
    }
}

查看

<table>
<tr>
    <td width="100px">Id </td>
    <td>Name</td>
</tr>


<?php foreach ($a as $value) { ?>
    <tr>
        <td>
        <?php print_r($value->id);?>
        </td>
        <td>
        <?php print_r($value->name);?>
        </td>
        <td> <?php dd($value->tags()); ?>
        <td>
    </tr> 
<?php } ?>
<table>

相关数据未显示 :( 鉴于此，请查看此内容并让我知道我错在哪里

【问题讨论】：

标签： php laravel associations

【解决方案1】：

对于单个标签，您可以这样做：

$tag = Tag::with(['posts', 'videos'])->find(1);
$relations = $tag->getRelations();

$posts = $relations['posts']; // Collection of Post models
$videos = $relations['videos']; // Collection of Video models

$allRelations = array_merge($posts->toArray(), $videos->toArray());

对于多个标签，您必须像这样编写自定义模型函数：

public function withTag($tag)
{
    foreach (func_get_args() as $arg) {
        $tags = ($arg instanceof Collection) ? $arg->all() : is_array($arg) ? $arg : array($arg);

        foreach ($tags as $t) {
            if (is_object($t)) {
                $this->filters[] = array('tag_id' => $t->id);
            }
            else {
                $this->filters[] = array('tag' => $t);
            }
        }
    }

    return $this;
}

【讨论】：

【解决方案2】：

*_type 列中的值必须具有命名空间。所以改变这个：

INSERT INTO `taggables` (`id`, `taggable_id`, `tag_id`, `taggable_type`) VALUES
(1, 1, 1, 'Post'),
(2, 2, 2, 'Video');

到

INSERT INTO `taggables` (`id`, `taggable_id`, `tag_id`, `taggable_type`) VALUES
(1, 1, 1, 'App\Post'),
(2, 2, 2, 'App\Video');

【讨论】：

【解决方案3】：

像这样更改您的 Post 模型。

class Post extends Model {
    public function taggable()
    {
        return $this->morphToMany();
    }
}

【讨论】：