Laravel在多对多关系中添加到两个模型的附加属性

// 创建中间表
Schema::create('model1_model2', function (Blueprint $table) {
    $table->unsignedBigInteger('model1_id');
    $table->unsignedBigInteger('model2_id');
    $table->string('additional_attribute');
    // 添加其他需要的列
    $table->timestamps();

    $table->foreign('model1_id')->references('id')->on('model1')->onDelete('cascade');
    $table->foreign('model2_id')->references('id')->on('model2')->onDelete('cascade');
});

// 模型1
class Model1 extends Model
{
    public function model2()
    {
        return $this->belongsToMany(Model2::class, 'model1_model2')
                    ->withPivot('additional_attribute');
    }
}

// 模型2
class Model2 extends Model
{
    public function model1()
    {
        return $this->belongsToMany(Model1::class, 'model1_model2')
                    ->withPivot('additional_attribute');
    }
}

// 添加附加属性
$model1 = Model1::find(1);
$model2 = Model2::find(1);
$model1->model2()->attach($model2, ['additional_attribute' => 'value']);

// 获取附加属性值
$additionalAttribute = $model1->model2->find(1)->pivot->additional_attribute;