Laravel 中数组类型字段的更新与多对多关系的最佳实践

class Recruitment extends Model
{
    use HasFactory;

    protected $fillable = [
        'title',
        'salary',
        'term_start',
        'term_end',
        'deadline',
        'details',
        'status',
        'applicants', // 允许批量赋值
    ];

    protected $casts = [
        'applicants' => 'array' // 将applicants字段自动转换为数组
    ];

    public function user(){
        return $this->belongsTo(\App\Models\User::class);
    }
}

public function up()
{
    Schema::create('recruitments', function (Blueprint $table) {
        $table->id();
        $table->string('title');
        $table->decimal('salary', 10, 2);
        $table->date('term_start');
        $table->date('term_end');
        $table->date('deadline');
        $table->longText('details');
        $table->string('status');
        $table->text('applicants')->nullable(); // 存储JSON格式的申请人ID数组
        $table->timestamps();
    });
}

use App\Models\Recruitment;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Auth;

class RecruitmentController extends Controller
{
    public function addApplicant($id, Request $request)
    {
        $job = Recruitment::findOrFail($id); // 使用 findOrFail 确保记录存在

        // 获取当前申请人ID数组，如果为空则初始化为空数组
        $currentApplicants = $job->applicants ?? [];

        $newApplicantId = $request->user_id;

        // 检查申请人是否已经存在，避免重复添加
        if (!in_array($newApplicantId, $currentApplicants)) {
            $currentApplicants[] = (int)$newApplicantId; // 添加新的申请人ID，确保类型一致
            $job->applicants = $currentApplicants; // 将更新后的数组重新赋值
            $job->save(); // 保存到数据库
        }

        return redirect()->back()->with('success', '您已成功申请该职位！');
    }
}

// database/migrations/xxxx_xx_xx_create_recruitment_user_table.php
use Illuminate\Database\Migrations\Migration;
use Illuminate\Database\Schema\Blueprint;
use Illuminate\Support\Facades\Schema;

class CreateRecruitmentUserTable extends Migration
{
    public function up()
    {
        Schema::create('recruitment_user', function (Blueprint $table) {
            $table->id();
            $table->foreignId('recruitment_id')->constrained()->onDelete('cascade');
            $table->foreignId('user_id')->constrained()->onDelete('cascade');
            $table->unique(['recruitment_id', 'user_id']); // 确保一个用户不能重复申请同一个职位
            $table->timestamps();
        });
    }

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

// app/Models/Recruitment.php
class Recruitment extends Model
{
    use HasFactory;

    protected $fillable = [
        'title', 'salary', 'term_start', 'term_end',
        'deadline', 'details', 'status'
        // 'applicants' 字段不再需要，因为我们使用枢纽表
    ];

    // 移除 protected $casts = ['applicants' => 'array'];

    // 定义与User模型的多对多关系
    public function applicants()
    {
        return $this->belongsToMany(\App\Models\User::class, 'recruitment_user', 'recruitment_id', 'user_id')
                    ->withTimestamps(); // 如果枢纽表有created_at和updated_at
    }
}

// app/Models/User.php
class User extends Authenticatable
{
    // ... 其他属性

    // 定义与Recruitment模型的多对多关系
    public function appliedJobs()
    {
        return $this->belongsToMany(\App\Models\Recruitment::class, 'recruitment_user', 'user_id', 'recruitment_id')
                    ->withTimestamps();
    }
}

use App\Models\Recruitment;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Auth;

class RecruitmentController extends Controller
{
    public function addApplicant($id, Request $request)
    {
        $job = Recruitment::findOrFail($id);
        $userId = Auth::id(); // 获取当前认证用户的ID

        // 使用 attach() 方法添加关联。如果已存在，则不会重复添加（因为枢纽表有unique约束）
        try {
            $job->applicants()->attach($userId);
            return redirect()->back()->with('success', '您已成功申请该职位！');
        } catch (\Illuminate\Database\QueryException $e) {
            // 如果唯一约束冲突，说明用户已经申请过
            if ($e->getCode() == 23000) { // MySQL的唯一约束错误码
                return redirect()->back()->with('error', '您已经申请过该职位了。');
            }
            throw $e; // 抛出其他数据库错误
        }
    }
}

// 原始答案的建议
public function user()
{
    return $this->belongsTo(User::class, 'applicants');
}
// 迁移文件也建议改为 $table->integer('applicants')->nullable();