php - 如何加入 Laravel 获取数据？

Question

我正在使用 Laravel 5，我有以下模型

组.php

class Group extends Model
{

    protected $fillable = ([
    'id'
    ]);

    public function users(){
        return $this->belongsToMany(
            'App\User',
            'user_group'
        );
    }

    public function posted(){
        return $this->hasMany(
            'App\PostGroup'
        );
    }
}

PostGroup.php

class PostGroup extends Model
{
    protected $fillable = [
        'group_id', 'user_id', 'post_content'
    ];

    public function user(){
        return $this->belongsTo('App\User');
    }

    public function group(){
        return $this->belongsTo('App\Group');
    }

    public function commented(){
        return $this->hasMany(
            'App\PostComment'
        );
    }
}

PostComment.php

class PostComment extends Model
{
    protected $fillable = [
        'post_id', 'user_id', 'comment_content'
    ];

    public function post(){
        return $this->belongsTo('App\PostGroup');
    }

    public function user(){
        return $this->belongsTo('App\User');
    }

}

在上下文中，我的 Web 应用程序提供了 groups，您可以在其中创建 posts 并且您可以在其中写 comments。所以，我的数据库中有以下关系:

• 组:(id、名称、描述)；
• 帖子组:(id, group_id, user_id, post_content);
• 发表评论:(id, post_id, user_id, comment_content);

我想做的是创建一个PostComment对象列表，然后进行查询获取一个组所有帖子的所有评论，在MySQL 看起来像:

SELECT post_comment.* FROM post_comment,post_group WHERE post_comment.post_id = post_group.id AND post_groups.group_id = 1;

现在，例如，在 Laravel 中，如果我想获取一个组的所有帖子，我有以下代码行:

$postList = Group::find($id)->posted->sortByDesc('created_at');

posted 是 Group Modal 中的一个函数。我试着做类似的事情

$commentList = PostGroup::where('group_id', $id)->commented;

但是还是不行，请问怎么解决？

编辑

组 Controller .php

/**
 * Display the specified resource.
 *
 * @param  int $id
 * @return \Illuminate\Http\Response
 */
public function show($id)
{
    // Replace with shares of publication-group-model
    $authUser =  Auth::user();
    $sharesList = Group::find($id)->shares->sortByDesc('created_at');
    $groupList = $authUser->groupsAsMember->where('id', '<>', $id);
    $group = $authUser->groups->find($id);
    $postList = Group::find($id)->posted->sortByDesc('created_at');

    $postsGroups = PostGroup::where('group_id', $id)->with('commented')->get(); 

    //dd($postsGroups);

    foreach ($postsGroups as $postGroup) {
        $commentsList = $postGroup->commented;
    }

    //dd($commentsList);

    return view('Pages.Group.detail', ['sharesList' => $sharesList, 'groupList' => $groupList, 'theGroup' => $group, 'postList' => $postList, 'commentsList' => $commentsList]);
}

Answer 1

Eloquent 的 HasManyThrough关系是为这种情况设计的，以允许访问远距离关系:

class Group extends Model
{
    public function comments()
    {
        return $this->hasManyThrough(
            PostComment::class, 
            PostGroup::class, 
            'group_id', 
            'post_id',
            'id', 
            'id'
        );
    }
}