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Creating a custom view renderer

There are many PHP template engines out there. Yii2 only offers native PHP templates. If you want to use one of the existing template engines or create your own one, you have to implement it—of course, if it's not yet implemented by the Yii community.

In this recipe we'll re-implement the Smarty templates support.

Getting ready

Create a new yii2-app-basic application using the composer, as described in the official guide at http://www.yiiframework.com/doc-2.0/guide-start-installation.html.
Install the Smarty library:
```
composer require smarty/smarty
```

How to do it…

Carry out the following steps for creating a custom view renderer:

Create the smarty/ViewRenderer.php file:

<?php
namespace appsmarty;

use Smarty;
use Yii;

class ViewRenderer extends yiiaseViewRenderer
{
    public $cachePath = '@runtime/smarty/cache';
    public $compilePath = '@runtime/smarty/compile';

    /**
    * @var Smarty
    */
    private $smarty;

    public function init()
    {
        $this->smarty = new Smarty();
        $this->smarty->setCompileDir(Yii::getAlias($this->compilePath));
        $this->smarty->setCacheDir(Yii::getAlias($this->cachePath));
        $this->smarty->setTemplateDir([
            dirname(Yii::$app->getView()->getViewFile()),
            Yii::$app->getViewPath(),
        ]);
    }

    public function render($view, $file, $params)
    {
        $templateParams = empty($params) ? null : $params;
        $template = $this->smarty->createTemplate($file, null, null, $templateParams, false);
        $template->assign('app', Yii::$app);
        $template->assign('this', $view);
        return $template->fetch();
    }
}

Now we need to connect the view renderer to the application. In config/web php, we need to add renderers of the view component:

'components' => [
    ....
    'view' => [
        'renderers' => [
            'tpl' => [
                'class' => 'appsmartyViewRenderer',
            ],
        ],
    ],
    ...
];

Now let's test it. Create a new SmartyController:

<?php
namespace appcontrollers;

use yiiwebController;

class SmartyController extends Controller
{
    public function actionIndex()
    {
        return $this->render('index.tpl', [
            'name' => 'Bond',
        ]);
    }
}

Next, we need to create the views/smarty/index.tpl view:

<div class="smarty-index">
    <h1>Smarty Example</h1>
    <p>Hello, {$name}!</p>
</div>

Now try running the controller. In a success case, you should get the following as output:

How it works…

A view renderer is a child of the yiiaseViewRenderer abstract class that implements only one method, called render:

<?php
namespace yiiase;

abstract class ViewRenderer extends Component
{
    /**
    * Renders a view file.
    *
    * This method is invoked by [[View]] whenever it tries to render a view.
    * Child classes must implement this method to render the given view file.
    *
    * @param View $view the view object used for rendering the file.
    * @param string $file the view file.
    * @param array $params the parameters to be passed to the view file.
    * @return string the rendering result
    */
   abstract public function render($view, $file, $params);
}

Therefore, we are getting a view component, file path, and render variables. We need to process the file and return the rendered result. In our case, processing itself is done by the Smarty template engine, so we need to properly initialize it and call its processing methods:

class ViewRenderer extends yiiaseViewRenderer
{
    public $cachePath = '@runtime/smarty/cache';
    public $compilePath = '@runtime/smarty/compile';
    private $smarty;

    public function init()
    {
        $this->smarty = new Smarty();
        $this->smarty->setCompileDir(Yii::getAlias($this->compilePath));
        $this->smarty->setCacheDir(Yii::getAlias($this->cachePath));
        $this->smarty->setTemplateDir([
            dirname(Yii::$app->getView()->getViewFile()),
            Yii::$app->getViewPath(),
        ]);
    }
    …
}

It is a good practice to store Yii temporary files in the application runtime directory. That is why we are setting the compile directory, where Smarty stores its templates compiled into PHP, to runtime/smarty/compile.

Rendering itself is a bit simpler:

public function render($view, $file, $params)
{
    $templateParams = empty($params) ? null : $params;
    $template = $this->smarty->createTemplate($file, null, null, $templateParams, false);
    $template->assign('app', Yii::$app);
    $template->assign('this', $view);
    return $template->fetch();
}

All data set via $this->render is passed to the Smarty template as it is. Also, we are creating special Smarty template variables named app and this that point to Yii::$app and Yii::$app->view and allow us to get application properties inside a template.

Then, we are rendering the templates.

Table of Contents for
Creating a custom view renderer

Creating a custom view renderer

Getting ready

How to do it…

How it works…

See also

Table of Contents for Creating a custom view renderer

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Creating a custom view renderer

Getting ready

How to do it…

How it works…

See also

Table of Contents for
Creating a custom view renderer