route('course_class'); $departmentId = $courseClass->course->department_id; return [ 'student_ids' => ['required', 'array', 'min:1'], 'student_ids.*' => [ 'integer', Rule::exists('students', 'id')->where('department_id', $departmentId), Rule::unique('class_enrollments', 'student_id')->where('course_class_id', $courseClass->id), ], ]; } }