Is it possible to extend twig with 'Twig_SimpleTest'?

Question

I was on the Twig StackExchange forum and found an answer that suited my needs.

But I can't for the life of me figure out how to implement this into a Craft CMS Plugin.

I'm familiar with Twig_Function_Method and Twig_Filter_Method, but I can't find anything on Twig_SimpleTest.

Has the option to include "tests" been omitted from Craft CMS?

Answer 1

When you call Craft's TemplatesService->getTwig() (craft()->templates->getTwig()), you get an instance of the Twig environment and from there you could be able to call addTest.

100% untested, but something like this should work:

$twig = craft()->templates->getTwig();
$twig->addTest(new My_Twig_SimpleTest());

Answer 2

Thanks Brad, that's what I was after. In the case of what I was trying to achieve; the following in my plugins init function did the job:

$twig = craft()->templates->getTwig();

$twig->addTest(new \Twig_SimpleTest('array', function ($value) {
  return is_array($value);
}));

I always struggle with syntax, so hopefully this example will help others.

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Craft 3 Solution:

Add this to your plugins main init() function:

$this->addTests(Craft::$app->view->getTwig());

Then add this function after the init():

private function addTests($twig) {
  // Is String
  $twig->addTest(new \Twig_SimpleTest('string', function ($value) {
    return is_string($value);
  }));
}