从父模型和子模型中获取特定字段

Question

我试图检索一个模型实例及其相关的一个，以便只从两者检索某些字段。这和这两个问题回答了如何为相关模型做到这一点，它对我来说很有效：

$hash = \Post::whereId(1075)
                        ->with(['thread' => function($query) {
                            $query->select('id', 'title');
                        }])
                        ->first()
                        ->toArray();
print_r($hash);
Array
(
    [id] => 1075
    [title] => Blablablablam,
    [text] => Blablablablablablabl,
    [created_at] => 2015-10-17 13:00:00
    [updated_at] => 2015-10-17 13:00:00
    [thread] => Array
        (
            [id] => 180
            [title] => Blablablablam
        )
)

但是，如果我也试图限制post模型的字段，则根本无法检索线程数据：

$hash = \Post::whereId(1075)
                        ->with(['thread' => function($query) {
                            $query->select('id', 'title');
                        }])
                        ->addSelect('title')
                        ->first()
                        ->toArray();
print_r($hash);
Array
(
    [title] => Blablablablam,
    [thread] => 
)

$hash = \Post::whereId(1075)
                        ->with(['thread' => function($query) {
                            $query->select('id', 'title');
                        }])
                        ->addSelect('title', 'thread_id')
                        ->first()
                        ->toArray();
print_r($hash);
Array
(
    [title] => Blablablablam,
    [thread_id] => 180,
    [thread] => Array
        (
            [id] => 180
            [title] => Blablablablam
        )
)

public function thread()
{
    return $this->belongsTo(Thread::class, 'thread_id');
}

Answer 1

未检索线程数据，因为还需要在post中选择外键