在on子句模型名称中使用多态数据透视表的laravel连接

Schema::create('commentables', function (Blueprint $table) {
    $table->id();
    $table->unsignedBigInteger('comment_id');
    $table->unsignedBigInteger('commentable_id');
    $table->string('commentable_type');
    $table->timestamps();

    $table->foreign('comment_id')->references('id')->on('comments')->onDelete('cascade');
});

class Comment extends Model
{
    public function commentable()
    {
        return $this->morphTo();
    }
}

class Post extends Model
{
    public function comments()
    {
        return $this->morphMany(Comment::class, 'commentable');
    }
}

class Video extends Model
{
    public function comments()
    {
        return $this->morphMany(Comment::class, 'commentable');
    }
}

$posts = Post::with(['comments' => function ($query) {
    $query->where('commentable_type', Post::class);
}])->get();

Schema::table('commentables', function (Blueprint $table) {
    $table->index(['commentable_type', 'commentable_id']);
});

$posts = Post::with(['comments' => function ($query) {
    $query->where('commentable_type', Post::class);
}])->paginate(10);