Laravel中Validator的验证扩展

虽然Laravel提供一套包括正则匹配在内的完善的验证机制，但你一定会遇到使用规则解决不了的验证，比如数据库验证，这时需要用到Validator的验证扩展。

（1）使用静态方法：Validator::extend
（2）使用对象调用：$validator->addExtension

下面是验证HTTP提交的商品分类信息的例子。

use \Illuminate\Http\Request;
use App\Exceptions\MyValidationException;
use App\GoodsCategory;

class GoodsValidator
{

    public static function validate(Request $request, $final = false)
    {
        $messages = [
            //'category_id.required' => ':attribute 输入不正确！',
            'category_id.required' => '抱歉，您输入的商品分类信息为空',
            'category_id.min' => '抱歉，您输入的商品分类信息长度有误',
            'category_id.category_id_check' => '抱歉，您输入的商品分类信息不存在',
        ];

        $rules = [
            'category_id' => 'required|min:4|category_id_check',
        ];

        Validator::extend('category_id_check', function($attribute, $value, $parameters) {
            return GoodsCategory::where('category_id', $value)->exists();
        });

        $validator = Validator::make($request->all(), $rules, $messages);
        /*
        $validator->addExtension('category_id_check', function($attribute, $value, $parameters) {
            return GoodsCategory::where('category_id', $value)->exists();
        });
        */
        if ($validator->fails()) {
            $messageBag = $validator->messages();
            $messageArr = $messageBag->getMessages();
            print_r($messageArr);
        }
    }

}