Laravel雄辩的关系在做任何事情时都不是对象，但dd() [英] Laravel Eloquent relationship not an object when doing anything but dd()

问题描述

我有一个看似愚蠢和疯狂的情况.我有用户的活动日志，我的用户模型具有这种关系:

I have a seemingly stupid and crazy situation. I have activity logs for users, my user model has this relationship in it:

public function activityLogs()
{
    return $this->hasMany(Log::class);
}

相当简单，当我检查单个用户对象的所有日志时，它工作正常.因此，在一页上，我只希望记录最后的日志，我需要其中的created_at日期.加载用户时，我会运行

Pretty straight forward and when I check a single user object for all logs it works fine. So on one page I only want the last log recorded, I need the created_at date from it. When loading the users I run

$users = User::with(
    [
        'activityLogs' => function ($query) {
            $query->orderBy('created_at', 'desc')
                  ->limit(1);
        }
    ]
)

，这将按预期返回最后一个日志.如果我想获取日期(如果我运行)

and this returns the last log as expected. When I want to get the date if I run

dd($users->first()->activityLogs()->first()->created_at->format("d/m/Y"));

我得到一个带有预期日期的字符串输出.但是，当我尝试对它进行任何其他处理时，例如将其放入变量中或将其回显，则只会收到一个错误，提示ActivityLogs()-> first()不是对象.我认为(在foreach ($users as $user)循环内)的代码是

I get a string output with the date as expected. However, when I try to do anything else with it, such as putting it into a variable or echoing it out I just get an error that activityLogs()->first() is not an object. The code in my view (inside a foreach ($users as $user) loop) is

{{ $user->activityLogs()->first()->created_at }}

这只会给我错误

ErrorException(E_ERROR) 尝试获取非对象的属性(视图: ROOT_PATH /resources/views/acp/partials/profiles.blade.php)(视图: ROOT_PATH /resources/views/acp/partials/profiles.blade.php)

ErrorException (E_ERROR) Trying to get property of non-object (View: ROOT_PATH/resources/views/acp/partials/profiles.blade.php) (View: ROOT_PATH/resources/views/acp/partials/profiles.blade.php)

我尝试将activityLogs作为集合和hasMany对象进行访问.我也尝试过用json_decode转换回生成的JSON字符串，但它仍然抱怨不是对象.

I've tried accessing activityLogs as both a collection and hasMany object. I've also tried converting the resultant JSON string back with json_decode but it still complains about not being an object.

为什么?为什么在使用dd时我可以得到很好的值，但是当我尝试其他任何方法时，它突然变成了JSON字符串?我尝试使用谷歌搜索，但是无论我尝试使用哪种单词组合，它都提出了有关如何将Eloquent对象转换为JSON的问题和指南，与我想要的相反.

Why? Why can I get the value perfectly fine when using dd but when I try anything else it's suddenly a JSON string? I've tried googling this but no matter what combination of words I try it just comes up with questions and guides on how to convert an Eloquent object into JSON, the opposite of what I want.

推荐答案

您需要检查以确保用户进行了最后一次活动.如果没有任何日志，first()将返回null.您应该检查循环中是否存在.

You need to check to make sure the user has a last activity. first() will return null if there aren't any logs. You should check for existence in your loop.

@foreach($user as $user)
    {{$user->activityLogs->count() > 0 ? $user->activityLogs->first()->created_at : 'User Has No Activity!'}}
@endforeach

或使用刀片服务器的@if/@else

@foreach($user as $user)
    @if($user->activityLogs->count() > 0)
        {{$user->activityLogs->first()->created_at}}
    @else 
        'User Has No Activity!'
    @endif  
@endforeach

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