Question

我有一个用户，学生，课程和主题表

Student表的user_id与我建立了一对一的关系，因为学生是用户。

因此，在我的学生报告中，我有一个创建功能，可以获得该学生目前注册的所有课程科目，我这样做了：

public function create()
{
    $user_id = Auth::user()->id;
    $student_id = Student::where('user_id', $user_id)->first();
    $course = $student_id->course->id;
    $subjects = Subject::where('course_id', $course)->get();
    return view('student.create', compact('subjects'));
}

视图如下所示：

{!! Form::open(['method' => 'POST', 'action'=>'StudentRegistration@store', 'files'=>true]) !!}
    @foreach($subjects as $subject)
    <div class="label-box">
        {!! Form::label('subject_id', $subject->name) !!}
        {!! Form::checkbox('subject_id[]', $subject->id, null, ['class'=>'form-control']) !!}
    </div>
    @endforeach
    <div class="form-group">
        {!! Form::submit('Create User', ['class'=>'btn btn-primary']) !!}
    </div>      
{!! Form::close() !!}

然后在store方法中，我设法更新数据透视表（student_subject）

  public function store(Request $request)
  {
    $data = $request->except('_token');
    $subject_count = count($data['subject_id']);
    for($i=0; $i < $subject_count; $i++){
       $student = Student::where('user_id', Auth::user()->id)->first();
       $student->subjects()->attach($data['subject_id'][$i]);
    }

但是，我注意到即使学生注册了某个特定科目，同一科目仍会在注册索引视图中显示，这将导致他进行双重注册。

那么，我怎样才能只查看学生所属的课程主题，而这些主题还没有在数据透视表中呢？

Answer 1

因为您正在使用Laravel Collections，我建议使用Laravel提供的以下方法。

https://laravel.com/docs/5.6/collections#method-diffassoc

希望这可以帮助您解决问题。

Answer 2

   Route::get('/studentsubjects', function(){
        $student_id = Student::where('user_id', Auth::id())->first();
        $course = $student_id->course->id;
        $subjects = json_decode($student_id->subjects);
        $subjects2 = json_decode(Subject::where('course_id', $course)->get());
        $subjectsUserNotRegisterd= array_udiff($subjects , $subjects2, function ($obj1, $obj2) {
            return $obj1->id-$obj2->id;
        });
        echo "<pre>", print_r($subjectsUserNotRegisterd, 1);
    });

结果：

Array
(
    [3] => stdClass Object
        (
            [id] => 5
            [course_id] => 1
            [lecturer_id] => 1
            [code] => Nss101
            [name] => Network Systems
            [created_at] => 2018-05-31 17:43:08
            [updated_at] => 2018-05-31 17:43:08
        )

)

Answer 3

我使用laravel docs将Route改为以下代码，它的工作原理非常完美：

Route::get('/studentsubjects', function(){
    $student_id = Student::where('user_id', Auth::id())->first();
    $course = $student_id->course->id;
    $all_subjects = $student_id->subjects;

    $selected_subjects = Subject::where('course_id', $course)->get();

    $nonregistered_subjects = $selected_subjects->diff($all_subjects);

    foreach ($nonregistered_subjects as $nonregistered) {
        echo $nonregistered->name;
    }
});

显示尚未在数据透视表中的记录

3 个答案: