Question

我有一个名为Exam的表

  Schema::create('exams', function (Blueprint $table) {
        $table->increments('id');
        $table->integer ('theory_score');
        $table->integer ('theory_coefficient');
        $table->integer ('practical_score');
        $table->integer ('practical_coefficient');
        $table->date('exam_date');

我希望在我的模型考试中创建一个功能totalMarks（）以便计算考试的总成绩像这样的东西

class Exam extends Model
    {
     protected $guarded = [];
   public function student() {
    return $this->belongsTo('App\Student', 'student_id', 'id');
   }
   public function totalMarks(){
     return (($this->theory_score*$this->theory_coefficient)+($this->practical_score*$this->practical_coefficient))/100;
   }

我想使用带有

的函数进行这样的查询

 public function getExam($studentId)
   {
     $exam = Exam::where('student_id','=',$studentId)
     ->with('student','totalMarks')->get()->toJson();
   return $exam; 
   }

我遇到此错误

“ message”：“在整数上调用成员函数addEagerConstraints（）”， “ exception”：“ Symfony \ Component \ Debug \ Exception \ FatalThrowableError”，

Answer 1

您可以使用accessor来完成这项工作：

class Exam extends Model
{

    public function student() {
        return $this->belongsTo(App\Student::class, 'student_id', 'id');
    }

    public function getTotalMarksAttribute() {
        return (($this->theory_score*$this->theory_coefficient)+($this->practical_score*$this->practical_coefficient))/100;
    }
...

如果要在从数据库中获取模型时进行计算，请使用retrieved事件（以下代码属于模型本身）：

protected static function boot()
{
    parent::boot();

    static::retrieved(function($exam) {
        $exam->attributes['total_marks'] = $exam->total_marks;
    });
}

为了检索您使用的计算属性

Exam::where(..)->first()->total_marks // single exam
Exam::where(..)->get()->pluck('total_marks') // collection of exams

Laravel：如何使用The with函数在Model中计算总分数并以JSON形式返回结果

1 个答案: