This is a quick post to discuss the rather simple view helper I created for rendering a Zend Framework style view file only if it exists. Generally asking the code to render a file which doesn’t exist will throw an exception. Therefore I created a wrapper for the Zend_View::render() method which determined whether the file exists and if so renders, otherwise simply returns an empty string.

Joost J. Bakker IJmuiden - http://www.flickr.com/photos/joost-ijmuiden/

Motivation

The motivation for this is that I have one controller/view/etc which shows slightly different output depending on a parameter. Some of these outputs have a related help information box defined, some do not. I didn’t want to have empty files hanging around my code just as much as I didn’t want to have try {} catch {} blocks in my view file. Therefore, I quickly created a ‘render if exists’ view helper for use in my code.

I realise that here I could have just wrapped the render method within a try{}catch{} within the view helper itself. In this case however any exceptions thrown from the rendered view would not bubble back up in the case of something going wrong.

How It Works

The view helper is created by extending Zend_View_Helper_Abstract as normally, this injected with the view upon use. The view helper is passed the view file you wish to render:

$this->renderIfExists('info-box.phtml');

Internally the object gathers the script paths from the view object and loops over them trying to find the file:

    /**
     * Check to see if a view script exists
     *
     * @return boolean
     */
    protected function _fileExists()
    {
        $paths = $this->view->getScriptPaths();
        foreach ($paths as $path) {
            if (file_exists($path . $this->_file)) {
                return true;
            }
        }
        return false;
    }

If a matching file is found it uses the standard Zend_View::render() method, otherwise it returns an empty string.

Summary

This is a very simple view helper to render a view file if it exists and simply return an empty string if not. It does not use a try{} catch{} block which would prevent any deeper exceptions being thrown from bubbling up and making themselves known. Instead it loops through the script paths defined within the view object and attempts to detect the file before trying to render it.

The full file can be found at my github repo.

Basically but invoking an instance of the front controller its possible to grab the router and assemble a url. Assemble is the function used in the view helper. The URL is built up from an array of module, controller, action, etc, followed by a second parameter of the route to use. The code is as follows:

<?php
/**
 * View helper which returns link category URL
 *
 * @author     Lloyd Watkin
 * @since      25/01/2010
 * @package    ViewHelper
 * @subpackage LinksUrl
 */
class Pro_View_Helper_LinksUrl
    extends Zend_View_Helper_Abstract
{
	/**
	 * Returns link category URL
	 *
	 * @param  Doctrine_Record $category
	 * @param  string          $module
	 * @param  string          $controller
	 * @param  string          $action
	 * @return string Url
	 */
    public function linksUrl($category, $module = 'www',
        $controller = 'links', $action = 'index')
    {
    	$router = Zend_Controller_Front::getInstance()->getRouter();

        return $router->assemble(array(
            'module'     => $module,
            'controller' => $controller,
            'action'     => $action,
            'category'   => "{$category->id}-{$category->name}",
        ), 'www-index');
    }
}

Another way to do this is to invoke Zend_View_Helper_Url itself and call the Url method (if you want to use the helper itself). This can be done by using the following code:

<?php
/**
 * View helper which returns link category URL
 *
 * @author     Lloyd Watkin
 * @since      25/01/2010
 * @package    ViewHelper
 * @subpackage LinksUrl
 */
class Pro_View_Helper_LinksUrl
    extends Zend_View_Helper_Abstract
{
	/**
	 * Returns link category URL
	 *
	 * @param  Doctrine_Record $category
	 * @param  string          $module
	 * @param  string          $controller
	 * @param  string          $action
	 * @return string Url
	 */
    public function linksUrl($category, $module = 'www',
        $controller = 'links', $action = 'index')
    {
    	$link = new Zend_View_Helper_Url();

        return $link->url(array(
            'module'     => $module,
            'controller' => $controller,
            'action'     => $action,
            'category'   => "{$category->id}-{$slug}",
        ), 'www-index');
    }
}

Both almost identical. Not a hard thing to do in the framework but can catch you out ;)