laravel遍历具有深厚关系的雄辩模型 [英] laravel looping through eloquent models with deep relationships

问题描述

以下循环有效:

foreach($this->friends as $friend)
{
    foreach($friend->mailings as $mailing)
    {
        foreach($mailing->orders as $order)
        {
            $num_orders++;
        }

    }
}

但是想做

foreach($this->friends->mailings->orders as $order)
{
    $num_orders++;
}

但是在执行此操作时出现此错误Property [mailings] does not exist on this collection instance.

but when I do I get this error Property [mailings] does not exist on this collection instance.

模型之间的关系已正确设置(有很多...等)

The relationship between models is setup correctly (has many...etc)

推荐答案

我找到了！ Jarek是Eloquent的一位出色作家，我想看看他是否有技巧.和往常一样，他做到了. :)

I found it! Jarek is a great writer for Eloquent, and I wanted to see if he had a trick for this. As always he does. :)

$this->load(['friends.mailings.orders' => function($q) use(&$orders){
    $orders = $q->get();
}]);

现在，如果您选择dd($orders)，您将获得与$this相关的朋友从邮件中收到的所有订单的列表，因此，您现在可以就此进行进一步的学习以获得想要的东西.

Now if you dd($orders) you will have a list of all orders from mailings from friends related to $this So you can now foreach over that to get what you want.

foreach($orders as $order){
    $num_orders++
}

他的网站上有证书警告，但这是我获得上述警告的地方. https://softonsofa.com/laravel-querying -任何级别的亲戚关系都带有简单的技巧/

His site has a certificate warning but this is where I got the above. https://softonsofa.com/laravel-querying-any-level-far-relations-with-simple-trick/

请忽略以下内容，因为不再需要它，但为了清楚起见，我将其保留在此处，因为它已被接受为答案.

您可以使用each()收集方法来清理循环.由于存在多对多关系，因此除非您对它们进行迭代或指定所需的相关项目，否则无法访问它们之间的关系.见下文:

You can use the each() collection method to clean up your loops. Since there are many-to-many relationships you can't access the related models relations unless you iterate over them or specify which related item you want. See below:

$this->friends->each(function($friend, $key){
    $friend->each(function($mailing, $key2){
        $mailing->orders->each(function($orders, $key3){
            $num_orders++;
        })  
    });
})

https://laravel.com/docs/5.8/collections#method-each

您可能还需要研究withCount()查询构建器方法.它似乎不喜欢使用常规点表示法的嵌套关系，但是我还没有足够使用它来说明是否可以在这里使用它.在查看 Laravel 5.3 withCount()嵌套关系 >部分.似乎有可能，但是您必须将您的关系更改为hasManyThrough().它应该是一个不错的起点.

There's also the withCount() query builder method that you may want to look into. It doesn't seem to like nested relations using the regular dot notation, but I haven't used it enough to say whether or not it can be used here. I stumbled upon Laravel 5.3 withCount() nested relation while looking into the withCount() part. Seems like it may be possible but you will have to change your relations to hasManyThrough(). It should be a good place to start.

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