Question

请注意：我对laravel和一般编程很陌生。

所以我在'user'和'role'之间有很多对很多的关系，并使用这个新东西，我刚刚学习了数据透视表'role_user'。现在，我想显示一个用户列表以及他们所拥有的角色的名称。

用户迁移

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

class CreateUsersTable extends Migration
{

    public function up()
    {
        Schema::create('users', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->string('name');
            $table->string('email')->unique();
            $table->timestamp('email_verified_at')->nullable();
            $table->string('password');
            $table->rememberToken();
            $table->timestamps();
        });
    }

    public function down()
    {
        Schema::dropIfExists('users');
    }
}

角色迁移

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

class CreateRolesTable extends Migration
{
    public function up()
    {
        Schema::create('roles', function (Blueprint $table) {
            $table->bigIncrements('id');
            $table->string('name');
        });
    }

    public function down()
    {
        Schema::dropIfExists('roles');
    }
}

角色用户迁移

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

class CreateRoleUserTable extends Migration
{
    public function up()
    {
        Schema::create('role_user', function (Blueprint $table) {
            $table->bigInteger('role_id')->unsigned();
            $table->bigInteger('user_id')->unsigned();
        });
    }

    public function down()
    {
        Schema::dropIfExists('role_user');
    }
}

用户模型

namespace App;

use Illuminate\Contracts\Auth\MustVerifyEmail;
use Illuminate\Foundation\Auth\User as Authenticatable;
use Illuminate\Notifications\Notifiable;

class User extends Authenticatable
{
    use Notifiable;

    protected $fillable = [
        'name', 'email', 'password', 'roles_id'
    ];

    protected $hidden = [
        'password', 'remember_token',
    ];

    protected $casts = [
        'email_verified_at' => 'datetime',
    ];

    public function roles()
    {
        return $this->belongsToMany('App\Role');
    }

    public function authorizeRoles($roles)
    {
        if (is_array($roles)) {
            return $this->hasAnyRole($roles) || 
                    abort(401, 'This action is unauthorized.');
        }
        return $this->hasRole($roles) || 
                abort(401, 'This action is unauthorized.');
    }
    /**
    * Check multiple roles
    * @param array $roles
    */
    public function hasAnyRole($roles)
    {
        return null !== $this->roles()->whereIn(‘name’, $roles)->first();
    }
    /**
    * Check one role
    * @param string $role
    */
    public function hasRole($role)
    {
        return null !== $this->roles()->where(‘name’, $role)->first();
    }
}

角色模型

namespace App;

use Illuminate\Database\Eloquent\Model;

class Role extends Model
{

    public $timestamps = false;

    public function users()
    {
        return $this->belongsToMany('App\User');
    }
}

我的观点

@extends('layouts/app')

@section('content')

<div class="row">
        <div class="col-md-12">
            <div class="card">
                <div class="card-header">
                    <h4>Users</h4>
                </div>

                <div class="panel-body">
                    @if (count($users) > 0)
                    <table class="table">
                        <thead>
                            <tr>
                                <th>Name</th>
                                <th>Email</th>
                                <th>Created on</th>
                                <th>Role</th>
                            </tr>
                        </thead>
                    @foreach ($users as $user)
                        <tr>
                                <td><em>{{$user->name}}</em></td>
                                <td><em>{{$user->email }} </em></td>
                                <td><em>{{$user->created_at}}</em></td>
                                <td><em>{{$user->roles->name}} </em></td> 
                                <td>
                                    <span class="table-remove">
                                         {!!Form::open(['action' =>['userController@destroy', $user->id], 'method' => 'POST'])!!}
                                            {{Form::hidden('_method', 'DELETE')}}
                                            {{ Form::button('<i class="fas fa-trash-alt" aria-hidden="true"></i>', ['class' => 'btn btn-danger btn-sm', 'type' => 'submit']) }}
                                        {!!Form::close()!!}
                                    </span>
                                </td>                                
                        </tr>
                    @endforeach
                    </table>
                </div>
            </div>
        </div>
    </div>
@else
    <p>No users found</p>

@endif

UserController

class UserController extends Controller
{
    public function index()
    {
        $users = User::all();
        return view('users.index',['users'=> $users]);
    }
}

现在我得到了错误：

属性[名称]在此集合实例上不存在。（查看：C：\ xampp \ htdocs \ Laravel \ AmbitieProject \ resources \ views \ users \ index.blade.php）

我尝试回显“ $ user-> roles-> name”，我认为它应该在一对多关系中起作用，但是我不确定如何使用多对多关系来回显角色的名称

Answer 1

您在定义关系时犯了一个错误。

请在关系中定义pivot表。

角色模型

public function users()
{
    return $this->belongsToMany('App\User', 'role_users'); //plural name
}

Answer 2

您的数据透视表将返回Laravel Collection。因此，您必须先获取记录，才能访问记录的属性。

如果有许多可能的角色（自从您使用数据透视表路由以来，我认为这是对的），则应执行类似的操作将其列出为逗号分隔的列表：

<td>
    <em>
        @if ($user->roles->count() > 0)
            {{ $user->roles->implode('name', ',') }}
        @endif
    </em>
</td>

如果只有一个角色，那么只需使用first()即可获得第一条记录：

<td>
    <em>
        @if ($user->roles->count() > 0)
            {{$user->roles->first()->name}} 
        @endif
    </em>
</td>

视图相关表中值的回显名称

2 个答案: