CourseWork/app/Http/Controllers/GradeTeacherController.php

<?php

namespace App\Http\Controllers;

use App\Http\Requests\GradeTeacherPostRequest;
use App\Models\Grade;
use App\Models\Subject;
use App\Models\Teacher;
use Illuminate\Http\RedirectResponse;
use Illuminate\View\View;

class GradeTeacherController extends Controller
{
    public function create(Teacher $teacher, Subject $subject): View
    {
        return view('grade-teacher.create', [
            'teacher' => $teacher,
            'subject' => $subject,
            'grades' =>  $subject->grades,
        ]);
    }

    public function store(GradeTeacherPostRequest $request, Teacher $teacher, Subject $subject): RedirectResponse
    {
        $teacher->grades()->syncWithoutDetaching($request->grade_id);

        return redirect()->route('teachers.subjects.show', [
            $teacher,
            $subject,
        ]);
    }

    public function edit(Teacher $teacher, Subject $subject, Grade $grade): View
    {
        return view('grade-teacher.edit', [
            'teacher' => $teacher,
            'subject' => $subject,
            'updateGrade' => $grade,
            'grades' => $subject->grades,
        ]);
    }

    public function update(GradeTeacherPostRequest $request, Teacher $teacher, Subject $subject, Grade $grade): RedirectResponse
    {
        $teacher->grades()->detach($grade);
        $teacher->grades()->attach($request->grade_id);

        return redirect()->route('teachers.subjects.show', [
            $teacher,
            $subject,
        ]);
    }

    public function destroy(Teacher $teacher, Subject $subject, Grade $grade): RedirectResponse
    {
        $teacher->grades()->detach($grade);

        return redirect()->route('teachers.subjects.show', [
            $teacher,
            $subject,
        ]);
    }
}