在Laravel中调用未定义的方法错误

Question

I have the following function:

public function addSubject(Request $request) {
    $student=User::find($request->invisible);
    $classsubjects = $request['classsubjects'];
    $student->classSubjects()->attach($cclasssubjects);
}

This gives me an error saying:

BadMethodCallException Call to undefined method Illuminate\Database\Query\Builder::attach()

Answer 1

The function classSubjects() in your Package model has to return a BelongsToMany relationship in order to use attach().

public function classSubjects() {
  return $this->belongsToMany('classSubjects');
}