Question

In Symfony2, when trying to render index.mobile.twig, How would I load index.html.twig when index.mobile.twig doesn’t exist. instead go getting a “this template does not exist error”.

I believe the answer lies somewhere with creating a custom loader for Twig but I couldn’t find any documentation on it, just occasional references to it.

Answer 1

The answer involves extending the twig.loader.class and creating an additional step once it’s discovered that the specific twig template doesn’t exist and before the Exception is thrown.

PART 1 – Configuration

The answer involves extending the twig.loader.class.

1. Create a customloader.php which extends the Twig FilesystemLoader file.

   namespace Acme\MyBundle\Twig\Loader;       
   use Symfony\Bundle\TwigBundle\Loader\FilesystemLoader;
   class CustomLoader extends FilesystemLoader{}
   

2. Modify your config.yml to include:

 parameters: 
     twig.loader.class: Acme\YourBundle\Twig\Loader\name_of_your_class

---

PART 2 – Extending the class

Extending the class is fairly straight forward.. The method I needed to modify was findTemplate($template). It’s very small method and you could probably use parent:: to extend the original code more properly.. However, I chose to completely over-write it and include the following code right before the Unable to find template error:

    if (false === $file || null === $file) {

        switch( $template->get('format')){
            case 'mobile':
                    $template->set('format','html');
                    return self::findTemplate($template->getLogicalName());
                break;
        }

        throw new \Twig_Error_Loader(sprintf('Unable to find template "%s".', $logicalName), -1, null, $previous);

After the code realizes that the file exists, it checks to see if mobile was the requested format. IF it is, it sets the format of the template object to html and then tries the name.html.twig. There’s a lot more you could do in this area but this solved my problem.