調用成員函數任務（）on null on laravel 5

Question

讓我用幾個字來解釋我的問題。 在我的控制，我有這樣一行：

$tasks = $student->group->tasks()->orderBy('created_at', 'desc')->withPivot('id')->get(); 

這適用於現有的用戶，但是當我嘗試創建新的我收到

Call to a member function tasks() on null

我可以像這樣的東西還是什麼做你建議？

if(!is_null($tasks)) 
    $tasks = $student->group->tasks()->orderBy('created_at', 'desc')->withPivot('id')->get(); 
} 

控制器上這我我的表演功能

public function show(){ 
    $user = Auth::user(); 

    if(!$user) 
     return redirect('/')->withErrors(config('constants.NA')); 

    $countries = Country::all()->lists('name', 'id')->toArray(); 
    $profile = $user->profile; 
    $student = $profile->student; 

    // Tasks showed on students profile 
    if ($student->group) { 
     $tasks = $student->group->tasks() 
      ->orderBy('created_at', 'desc') 
      ->withPivot('id') 
      ->get(); 
    } 
    // Classmates 
    if ($student->group) { 
     $classmates = $student->group->students() 
     ->where('id', '!=', $student->id) 
     ->get(); 

    } 

    // Activated books 
    $books = Auth::user()->books()->orderBy('grade_id', 'asc')->get(); 


    if(!is_null($student->group)) 
    $iTasks = $student->group->tasks->count(); 
    else { 
    $iTasks = 0; 
    } 

    $iTodos = $user->todos->count(); 

    return view('student.profile.show',compact('user','profile', 'countries', 'iTasks', 'iTodos', 'tasks', 'classmates', 'books')); 
} 

這是我的表演來看，對於任務

<div class="tab-pane <?php if(isset($tab) && $tab == 'timeline'): ?> active <?php endif; ?>" id="timeline"> 
         @if($tasks->count()) 
          <div class="timeline"> 
          @foreach($tasks as $task) 
           <!-- TIMELINE ITEM --> 
           <div class="timeline-item"> 
           <div class="timeline-badge"> 
            <div class="timeline-icon"> 
            <i class="mdi mdi-clipboard-text font-red-intense"></i> 
            </div> 
           </div> 
           <div class="timeline-body"> 
            <div class="timeline-body-arrow"> </div> 
            <div class="timeline-body-head"> 
            <div class="timeline-body-head-caption"> 
             <span class="timeline-body-title font-blue-madison"> 
             {{ $task->professor->profile->user->name }} 
             </span> 
             <span class="timeline-body-time font-grey-cascade">ju ca caktuar një <a href="/student/tasks" class="font-red sbold">detyrë</a> të re.</span> 
            </div> 
            </div> 
            <div class="timeline-body-content"> 
            <span class="font-grey-cascade"> 
             {{ $task->pivot->comment }} 
            </span> 
            </div> 
            <hr> 
            Lenda: <span class="timeline-body-time font-grey-cascade sbold">{{ $task->subject->name }}</span> 
            <div class="pull-right"> 
            Krijuar më: <span class="timeline-body-time font-grey-cascade sbold">{{ $task->created_at->format(Config::get('klasaime.date_format')) }}</span> 
            </div> 
           </div> 
           </div> 
           <!-- END TIMELINE ITEM --> 
          @endforeach 
          </div> 
         @else 
          <div class="alert"> 
          Ju nuk keni asnje detyrë të caktuar! 
          </div> 
         @endif 
         </div> 

Answer 1

看起來像你對我有沒有學生加入還沒有成功，或者某種程度上沒有被堅持。如果你已經創建和保存學生後添加學生一組，試試這個：

$student->load('group') 

運行之前：

$tasks = $student->group->tasks()->orderBy('created_at', 'desc')->withPivot('id')->get(); 

我需要看到更多的代碼，以提供更準確的答案。但是你得到的錯誤與你的學生的->group有關，而不是你的學生本身。

Answer 2

做一個簡單的檢查，看看該組是否存在，然後繼續進行你需要執行的任何操作。

// controller 
$tasks = null; 

if ($student->group) { 
    $tasks = $student->group->tasks() 
     ->orderBy('created_at', 'desc') 
     ->withPivot('id') 
     ->get(); 
} 

// view 
@if($tasks) 
    {{ $tasks->id }} 
@else 
    No tasks found 
@endif 

編輯：在您的控制器在頂部添加$tasks = null;和$classmates = null;。並在您的視圖中將@if($tasks->count())更改爲@if($tasks)。我不確定你在哪裏使用同學變量，但在使用之前添加一個檢查以確定它是否爲空。