无法将类的对象转换为字符串Symfony2错误

Question

我收到此错误：

在第13行的form_div_layout.html.twig中，在呈现模板期间抛出了异常（“Catchable致命错误：类Mihail \ SearchBundle \ Entity \ FileSearch的对象无法转换为字符串”）。

使用symfony 2.8LTS。 以下是我用来基本上在我自己的包中创建搜索表单的文件，它根据表单中提供的搜索条件在app目录中搜索。 搜索控制器：

<?php

 namespace Mihail\SearchBundle\Controller;

 use Symfony\Bundle\FrameworkBundle\Controller\Controller;
 use Sensio\Bundle\FrameworkExtraBundle\Configuration\Route;
 use Mihail\SearchBundle\Entity\FileSearch;
 use Symfony\Component\Finder\Finder;
 use Symfony\Component\HttpFoundation\Request;
 use Mihail\SearchBundle\Form\Type\SearchType;

 class SearchController extends Controller
 {
     /**
      * @Route("/search")
      */
     public function searchAction(Request $request)
     {
         $search = new FileSearch();

        $dirsList = $this->generateDirsList();

         $form = $this->createForm(SearchType::class, $search, array('dirs_list' => $dirsList));

         $form->handleRequest($request);

        if ($form->isSubmitted() && $form->isValid()) {
            $searchContent = $form->get('searchContent')->getData();
            $fileType = $form->get('fileType')->getData();
            $searchDir = $form->get('searchDir')->getData();

            $finder = new Finder();
            if(isset($fileType))
            {
                $finder->files()->name("*.$fileType");
            }

            if(isset($searchDir))
            {
                $finder->files()->in($searchDir);
            }else{
                $finder->files()->in(__DIR__);
            }

            if(isset($searchContent))
            {
                $finder->contains($searchContent);
            }

            if(isset($finder) && count($finder)>0)
            {
                echo "Found results in $searchDir: <br/>";
                foreach ($finder as $key => $value) {
                    echo "<h4> $value contains '$searchContent' </h4>";
                }
            }else{
                echo "No content '$searchContent' in '$searchDir'";
            }
        }

         return $this->render('MihailSearchBundle:randomsearch:search_form.html.twig', array(
             'form' => $form->createView(),
         ));
     }

     public function generateDirsList()
     {
        $path = $this->get('kernel')->getRootDir();
        $finder = new Finder();

        $iterator = $finder
            ->ignoreUnreadableDirs()
            ->directories()
            ->depth('< 2')
            ->in($path);

        $dirsList = array();
        foreach ($iterator as $key => $value) {
            $dirsList["$value"] = "$value";
        }

        return $dirsList;
     }
 }

获取并设置文件搜索字段

<?php

 namespace Mihail\SearchBundle\Entity;

 use Symfony\Component\Validator\Constraints as Assert;

 class FileSearch
 {

    protected $searchContent;

    protected $fileType;

    protected $searchDir;

    public function getSearchContent()
     {
         return $this->searchContent;
     }

     public function setSearchContent($searchContent)
     {
         $this->searchContent = $searchContent;
     }

     public function getFileType()
     {
        return $this->fileType;
     }

     public function setFileType($fileType)
     {
        $this->fileType = $fileType;
     }

     public function getSearchDir()
     {
        return $this->searchDir;
     }

     public function setSearchDir($searchDir)
     {
        $this->searchDir = $searchDir;
     }
 } 

用于创建表单的搜索类型

<?php

 namespace Mihail\SearchBundle\Form\Type;

 use Symfony\Component\Form\AbstractType;
 use Symfony\Component\Form\FormBuilderInterface;
 use Symfony\Component\Form\Extension\Core\Type\TextType;
 use Symfony\Component\Form\Extension\Core\Type\ChoiceType;
 use Symfony\Component\Form\Extension\Core\Type\SubmitType;
 use Symfony\Component\OptionsResolver\OptionsResolver;

 class SearchType extends AbstractType
 {
    public function buildForm(FormBuilderInterface $builder, array $options)
     {
         $builder
             ->add('searchContent', TextType::class, array('label'=> 'Search Content:* '))
             ->add('fileType', TextType::class , array('label'=> 'File Type:'))
             ->add('searchDir',  ChoiceType::class, array(
                'label' => 'Search Path:',
                'choices' => $options['dirs_list'],
                'choices_as_values' => true))
             ->add('save', SubmitType::class, array('label' => 'Search for File'));
     }

     public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setRequired(array(
            'dirs_list',
        ));

        $resolver->setDefaults(array(
            'data_class' => 'Mihail\SearchBundle\Entity\FileSearch',
            'dirs_list' => null,
        ));
    }
 } 

用于呈现表单字段的简单树枝模板

{# Mihail/SearchBudnle/Resources/views/randomsearch/search_form.html.twig #}

    {{ form(form, {'attr': {'novalidate': 'novalidate'}}) }}
    {{ form_start(form) }}
        {{ form_row(form.fileType) }}
        {{ form_row(form.searchContent) }}
        {{ form_row(form.searchDir) }}
    {{ form_end(form) }}

任何想法我做错了什么？