Laravel Vuejs 实战：开发知乎 （17）实现提交答案

1.添加路由 并 处理AnswerController内逻辑：

路由：向web.php中添加：

#region 回答路由CRUD

//查看回答 以及 回答的form 都是在questions详细内容页面

//提交回答
Route::post('questions/{question}/answers', 'AnswerController@store')->name('answers.store');

//更新回答


//删除回答


#endregion

<?php

/*
|--------------------------------------------------------------------------
| Web Routes
|--------------------------------------------------------------------------
|
| Here is where you can register web routes for your application. These
| routes are loaded by the RouteServiceProvider within a group which
| contains the "web" middleware group. Now create something great!
|
*/

Route::get('/', function () {
    return view('welcome');
});

Auth::routes(['verify' => true]);

Route::get('/home', 'HomeController@index')->name('home');

Route::resource('questions', 'QuestionController');


#region 回答路由CRUD

//查看回答 以及 回答的form 都是在questions详细内容页面

//提交回答
Route::post('questions/{question}/answers', 'AnswerController@store')->name('answers.store');

//更新回答


//删除回答


#endregion

AnswerController.php最后更新见文末

2.在question详情内页 添加提交回答的form

最后更新见文末 show.blade.php

3.提交后由于要给Question和User模型内赋值 answer_id 所以在$fillable属性里加上'answer_id'：

不赋值！见后文根据 一对多关系处说明。不存所以表里之前的字段要删除，也就更不可能赋值了

在处理一对多的时候

Php Laravel框架 多表关系处理 之 Eloquent一对多关系处理

Laravel One to Many Eloquent Relationship Tutorial

多对多的时候：

Laravel中的 Pivot 表与多对多关系s

一对多关系，在创建answer模型的时候，需要更新user 和 question 里面的 answer_id，

不需要更新！见后文根据 一对多关系处说明。不存所以表里之前的字段要删除，也就更不可能需要更新了

之前忘了在anwers 的 migration里加外键；

【模型之间通过模型关联方法 已经默认配置了外键 讲解：一对多】

laravel模型表建立外键约束的使用：

模型：

//表->posts
class Post extends Model
{
    //关联用户：
    public function user(){
        //belongsTo,第一个参数：外键表,第二个：当前表的外键，第三个：外渐表的主键。
        //如果第二个是名词+id,第三个是：id。后面的两个参数可以省略：
        // return $this->belongsTo('App\User');
        return $this->belongsTo('App\User','user_id','id');
    }
}

视图中的调用：下面的会输出：posts表中user_id对应的user表中的id的name值

<a href="#">{{$post->user->name}}</a></p>

现在加上，执行命令：

php artisan make:migration add_foreign_key_relationship_to_answers_table --table=answers

注意是answers表；

<?php

use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

class AddForeignKeyRelationshipToAnswersTable extends Migration
{
    /**
     * Run the migrations.
     *
     * @return void
     */
    public function up()
    {
        Schema::table('answers', function (Blueprint $table) {
            //
            $table->foreign('user_id')->references('id')->on('users');
            $table->foreign('question_id')->references('id')->on('questions');
        });
    }

    /**
     * Reverse the migrations.
     *
     * @return void
     */
    public function down()
    {
        Schema::table('answers', function (Blueprint $table) {
            //
            $table->dropForeign('answers_user_id_foreign');
            $table->dropForeign('answers_question_id_foreign');
        });
    }
}

注意foreign key的命名：answers_user_id_foreign  查阅： Foreign Key Constraints 

然后执行：

php artisan migrate

---

根据 一对多关系：

主表不存子表的id：用户不存回答的id，问题不存回答的id，

子表存储主表的id：回答存储用户的id，回答存储问题的id，并设置外键，可以使用save saveMany associate再save方法；

具体请查阅： Laravel One to Many Eloquent Relationship Tutorial

所以我们需要移除之前再Quesiton和User表中的answer_id字段；代码省略

多对多的表：

新建立第三个表  还要使用attach sync detach方法操作更新

以上都必须设置模型关联

具体请查阅：Laravel Many to Many Eloquent Relationship Tutorial

show.blade.php:

@extends('layouts.app')
@section('content')
    <div class="container">
        <div class="row">
            <div class="col-md-8 col-md offset-2">
                {{--问题--}}
                <div class="card">
                    <div class="card-header">
                        {{ $question->title }}

                        @foreach(['success','warning','danger'] as $info)
                            @if(session()->has($info))
                                <div class="alert alert-{{$info}}">{{ session()->get($info) }}</div>
                            @endif
                        @endforeach

                        @can('update',$question)
                            <a href="{{ route('questions.edit',$question) }}" class="btn btn-warning">编辑</a>
                        @endcan

                        @can('destroy',$question)
                            <form action="{{ route('questions.destroy',$question) }}" method="post">
                                @csrf
                                @method('DELETE')
                                <button type="submit" class="btn btn-danger">删除</button>
                            </form>
                        @endcan

                        @forelse($question->topics as $topic)
                            <button class="btn btn-secondary float-md-right m-1">{{ $topic->name }}</button>
                        @empty
                            <p class="text text-warning float-md-right"> "No Topics"</p>
                        @endforelse

                        <p class="text text-info float-md-right"> 已有{{ count($question->answers) }}个回答</p>

                    </div>
                    <div class="card-body">
                        {!! $question->content !!}
                    </div>
                </div>


                {{--回答提交form--}}

                <div class="card mt-2">
                    <div class="card-header">
                        提交回答
                    </div>
                    <div class="card-body">
                        <form action="{{ route('answers.store',$question) }}" method="post">
                        @csrf
                        <!-- 回答编辑器容器 -->
                            <script id="container" name="content" type="text/plain"
                                    style="width: 100%;height: 200px">{!! old('content') !!}</script>
                            <p class="text text-danger"> @error('content') {{ $message }} @enderror </p>
                            <!--提交按钮-->
                            <button type="submit" class="btn btn-primary mt-2 float-md-right">提交回答</button>
                        </form>
                    </div>
                </div>

                {{--展示答案--}}
                @forelse($question->answers as $answer)
                    <div class="card mt-4">
                        <div class="card-header">
                            <div class="float-left">
                                <img src="{{ $answer->user->avatar }}" class="img-thumbnail imgWrap"
                                     style="height: 50px" alt="{{ $answer->user->name }}">
                                <span class="text text-info">{{ $answer->user->name }}</span>
                            </div>
                            <span class="float-right text text-info m-auto">{{ $answer->updated_at }}</span>
                        </div>

                        <div class="card-body">
                            {!!  $answer->content  !!}
                        </div>
                    </div>

                @empty

                @endforelse
            </div>
        </div>
    </div>
@endsection
@section('footer-js')
    @include('questions._footer_js')
@endsection

QuestionController.php:

<?php

namespace App\Http\Controllers;

use App\Http\Requests\QuestionStoreRequest;
use App\Models\Question;
use App\Repositories\QuestionRepository;


class QuestionController extends Controller
{

    /**
     * @var QuestionRepository
     */
    private $questionRepository;

    public function __construct(QuestionRepository $questionRepository)
    {
        $this->middleware(
            'auth',
            [
                'except' =>
                    [
                        'index',
                        'show',
                    ]//非注册用户只能查看不能编辑添加更改删除
            ]
        );

        $this->questionRepository = $questionRepository;
    }


    /** Display a listing of the resource.
     * @return \Illuminate\Contracts\View\Factory|\Illuminate\View\View
     */
    public function index()
    {
        //
        $questions = $this->questionRepository->getQuestionPublished();
        return view('questions.index', compact('questions'));
    }


    /**
     * @return \Illuminate\Contracts\View\Factory|\Illuminate\View\View
     */
    public function create()
    {
        //
        return view('questions.create');
    }


    /**
     * @param QuestionStoreRequest $request
     * @return \Illuminate\Http\RedirectResponse
     */
    public function store(QuestionStoreRequest $request)//依赖注入QuestionStoreRequest实例
    {
        //
//        $data = $request->validate([
//            'title' => 'required|min:8',
//            'content' => 'required|min:28',
//        ]);
        //存储topics
        $topics = $this->questionRepository->normalizeTopics($request->get('topics'));
        //初始化question要用到的数据
        $data = $request->all();
        $data['user_id'] = auth()->user()->id;

//        $question=Question::create($data); 被下方代码取代
        $question = $this->questionRepository->create($data);

        //使用我们再question model里面添加的topics方法获得 topics关联，再使用attach方法
        $question->topics()->attach($topics);

        return redirect()->route('questions.show', $question);
    }


    /**
     * @param Question $question
     * @return \Illuminate\Contracts\View\Factory|\Illuminate\View\View
     */
    public function show(Question $question)
    {
        //使用关系关联加载，with方法会将分类之下的主题一起查询出来，而且不会出现N+1影响性能的问题
        $question->with('topics')->get();
        //使用关系关联加载，with方法会将分类之下的回答一起查询出来，而且不会出现N+1影响性能的问题
        $question->with('answers')->get();

        return view('questions.show', compact('question'));
    }


    /**判断权限 返回视图
     * @param Question $question
     * @return \Illuminate\Contracts\View\Factory|\Illuminate\Http\RedirectResponse|\Illuminate\View\View
     */
    public function edit(Question $question)
    {
        if (auth()->user()->can('update', $question)) //判断当前用户是否有权编辑更新该question实例
        {
            //返回编辑视图
            return view('questions.edit', compact('question'));
        } else {
            //返回警告 没有权限
            return redirect()->back()->with('warning', '你不能编辑不属于你的问题！');
        }
    }


    /** Update the specified resource in storage.
     * @param QuestionStoreRequest $questionStoreRequest
     * @param Question $question
     * @return \Illuminate\Http\RedirectResponse
     */
    public function update(QuestionStoreRequest $questionStoreRequest, Question $question)
    {
        //更新前 判断下权限
        if (!(auth()->user()->can('update', $question))) {
            //返回警告 没有权限
            return redirect()->back()->with('warning', '你不能编辑不属于你的问题！');
        }
        //取得更新的字段 使用Eloquent提供的update方法执行问题更新
        $question->update([
            'title' => $questionStoreRequest->get('title'),
            'content' => $questionStoreRequest->get('content'),
        ]);


        //topics的操作这时候看起来有点臃肿 可以使用TopicController来管理，暂时省略
        //存储topics
        $topics = $this->questionRepository->normalizeTopics($questionStoreRequest->get('topics'));
        //使用我们再question model里面添加的topics方法获得 topics关联，
        //再使用sync方法同步tag 【删除的会被删除掉，没删除的就保留，新的就增加】
        $question->topics()->sync($topics);

        //更新完成，跳转回去
        return redirect()->back();
    }


    /**Remove the specified resource from storage.
     * @param Question $question
     * @return \Illuminate\Http\RedirectResponse
     * @throws \Exception
     */
    public function destroy(Question $question)
    {
        //
        if (auth()->user()->can('destroy', $question)) {
            $question->delete();
            return redirect()->route('questions.index')->with('success', "删除成功！");
        }
        return redirect()->back()->with('danger', "你不能删除不属于你的问题！");
    }


}

AnswerController.php：

<?php

namespace App\Http\Controllers;

use App\Answer;
use App\Models\Question;
use Illuminate\Http\Request;

class AnswerController extends Controller
{

    /**
     * AnswerController constructor.
     */
    public function __construct()
    {
        //只有登录用户才能回答问题 但是可以查看 和查看提交创建页面，引导用户去注册
        $this->middleware(['auth',])->except(['index', 'create', 'show']);
    }

    /**
     * Display a listing of the resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function index()
    {
        //
    }

    /**
     * Show the form for creating a new resource.
     *
     * @return \Illuminate\Http\Response
     */
    public function create()
    {
        //
    }


    /** Store a newly created resource in storage.
     * @param Request $request
     * @param Question $question
     * @return \Illuminate\Http\RedirectResponse
     */
    public function store(Request $request, Question $question)
    {
        //


        //初始化回答数据
        $data = $request->validate([
            'content' => 'required|min:30',
        ]);
        $data['user_id'] = auth()->user()->id;

        $data['question_id'] = $question->id;

        //创建回答入库
        $answer = Answer::create($data);
        //更新问题里的数据
        $question->increment('answers_count');
        //更新用户里的数据
        auth()->user()->increment('answers_count');
        return redirect()->back()->with('success', "回答成功！");
    }

    /**
     * Display the specified resource.
     *
     * @param \App\Answer $answer
     * @return \Illuminate\Http\Response
     */
    public function show(Answer $answer)
    {
        //
    }

    /**
     * Show the form for editing the specified resource.
     *
     * @param \App\Answer $answer
     * @return \Illuminate\Http\Response
     */
    public function edit(Answer $answer)
    {
        //
    }

    /**
     * Update the specified resource in storage.
     *
     * @param \Illuminate\Http\Request $request
     * @param \App\Answer $answer
     * @return \Illuminate\Http\Response
     */
    public function update(Request $request, Answer $answer)
    {
        //
    }

    /**
     * Remove the specified resource from storage.
     *
     * @param \App\Answer $answer
     * @return \Illuminate\Http\Response
     */
    public function destroy(Answer $answer)
    {
        //
    }
}

Answer.php

<?php

namespace App;

use App\Models\Question;
use Illuminate\Database\Eloquent\Model;
use Illuminate\Database\Eloquent\SoftDeletes;

class Answer extends Model
{
    #region 支持软删除添加
    use SoftDeletes;
    protected $dates = ['deleted_at'];

    #endregion

    protected $fillable = ['user_id', 'question_id', 'content'];

    /** 一个回答只有一个回答主人
     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
     */
    public function user()
    {
        return $this->belongsTo(User::class);
    }

    /** 一个回答只针对一个问题
     * @return \Illuminate\Database\Eloquent\Relations\BelongsTo
     */
    public function question()
    {
        return $this->belongsTo(Question::class);
    }

}