<?php
// app/AppKernel.php

// ...
class AppKernel extends Kernel
{
    public function registerBundles()
    {
        $bundles = array(
            // ...
            new HDevs\UploaderBundle\HDevsUploaderBundle(),
        );

        // ...
    }

    // ...
}

<?php
//Entity

use HDevs\UploaderBundle\Annotation\Uploadable;
use HDevs\UploaderBundle\Annotation\UploadableProperty;
/**
 * @ORM\Table(name="post")
 * @Uploadable()
 */
class Post
{
    // Other fields
    
    /**
     * @var string
     * @ORM\Column(name="image", type="string", length=255)
     */
    private $image;

    /**
     * @var \DateTime
     * @ORM\Column(name="updated_at", type="datetime", nullable=true)
     */
    private $updatedAt;

    /**
     * @var File
     * @UploadableProperty(field="image", path="uploads/posts")
     */
    private $file;
}

<?php
//FormType

use Symfony\Component\Form\Extension\Core\Type\FileType;
$builder->add('file', FileType::class, [
                'label' => 'global.image'
            ]);