Symfony2 和 Twig - 检查资产是否存在

I have a symfony2 project using twig templates.

I am displaying some images and would like to display the image only if the specific asset exists.

I have this:

{% if asset('bundles/sciforumversion2/images/logos/'~conf.img) %}
    <img style="width: 60px; float:right; margin-right: 15px;" src="{{ asset('bundles/sciforumversion2/images/logos/')}}{{ conf.img }}"/>
{% endif %}

But the if condition is always true.

Any idea please? Thank you.

解决方案

If you want to check if an asset exists, you can create a Twig extension to implement the function.

PHP In your TwigExtension directory, create AssetExistsExtension.php with the following content:

<?php

namespace FuzTestBundleTwigExtension;

use SymfonyComponentHttpKernelKernelInterface;

class AssetExistsExtension extends Twig_Extension
{

    private $kernel;

    public function __construct(KernelInterface $kernel)
    {
        $this->kernel = $kernel;
    }

    public function getFunctions()
    {
        return array(
                'asset_exists' => new Twig_Function_Method($this, 'asset_exists'),
        );
    }

    public function asset_exists($path)
    {
        $webRoot = realpath($this->kernel->getRootDir() . '/../web/');
        $toCheck = realpath($webRoot . $path);

        // check if the file exists
        if (!is_file($toCheck))
        {
            return false;
        }

        // check if file is well contained in web/ directory (prevents ../ in paths)
        if (strncmp($webRoot, $toCheck, strlen($webRoot)) !== 0)
        { 
            return false;
        }

        return true;
    }

    public function getName()
    {
        return 'asset_exists';
    }

}

YML And here is the configuration, to put in your services.yml file.

parameters:
    (...)
    fuz_tools.twig.asset_exists_extension.class: FuzTestBundleTwigExtensionAsset@ExistsExtension

services:
    (...)
    fuz_tools.twig.asset_exists_extension:
        class: '%fuz_tools.twig.asset_exists_extension.class%'
        arguments: ['@kernel']
        tags:
          - { name: twig.extension }

Twig To use this extension, on a twig file, use:

{% if asset_exists('bundles/fuztest/images/test.png') %}

Note: do not forget to replace namespaces to match with your project.