Using Latte with Slim 4
***********************

.[perex]
This article written by "Daniel Opitz":https://odan.github.io/2022/04/06/slim4-latte.html describes how to use Latte with the Slim Framework.

First, "install the Slim Framework":https://odan.github.io/2019/11/05/slim4-tutorial.html and then Latte using Composer:

```shell
composer require latte/latte
```


Configuration
-------------

Create a new directory `templates` in your project root directory. All templates will be placed there later.

Add a new `template` configuration key in your `config/defaults.php` file:

```php
$settings['template'] = __DIR__ . '/../templates';
```

Latte compiles the templates to native PHP code and stores them in a cache on the disk. So they are as fast as if they had been written in native PHP.

Add a new `template_temp` configuration key in your `config/defaults.php` file: Make sure the directory `{project}/tmp/templates` exists and has read and write access permissions.

```php
$settings['template_temp'] = __DIR__ . '/../tmp/templates';
```

Latte automatically regenerates the cache every time you change the template, which can be turned off in the production environment to save a little performance:

```php
// change to false in the production environment
$settings['template_auto_refresh'] = true;
```

Next, add a DI container definitions for the `Latte\Engine` class.

```php
<?php

use Latte\Engine;
use Latte\Loaders\FileLoader;
use Psr\Container\ContainerInterface;
// ...

return [

	// ...

	Engine::class => function (ContainerInterface $container) {
		$latte = new Engine();
		$settings = $container->get('settings');
		$latte->setLoader(new FileLoader($settings['template']));
		$latte->setTempDirectory($settings['template_temp']);
		$latte->setAutoRefresh($settings['template_auto_refresh']);

		return $latte;
	},
];
```

This alone would technically work to render a Latte template, but we also need to make it work with the PSR-7 response object.

For this purpose we create a special `TemplateRenderer` class which does this work for us.

So next create a file in `src/Renderer/TemplateRenderer.php` and copy/paste this code:

```php
<?php

namespace App\Renderer;

use Latte\Engine;
use Psr\Http\Message\ResponseInterface;

final class TemplateRenderer
{
	public function __construct(
		private Engine $engine,
	) {
	}

	public function template(
		ResponseInterface $response,
		string $template,
		array $data = [],
	): ResponseInterface
	{
		$string = $this->engine->renderToString($template, $data);
		$response->getBody()->write($string);

		return $response;
	}
}
```


Usage
-----

Instead of using the Latte Engine object directly we use the `TemplateRenderer` object to render the template into a PSR-7 compatible object.

A typical Action handler class might look like this to render a template with the name `home.latte`:

```php
<?php

namespace App\Action\Home;

use App\Renderer\TemplateRenderer;
use Psr\Http\Message\ResponseInterface;
use Psr\Http\Message\ServerRequestInterface;

final class HomeAction
{
	public function __construct(
		private TemplateRenderer $renderer,
	) {
	}

	public function __invoke(
		ServerRequestInterface $request,
		ResponseInterface $response,
	): ResponseInterface
	{
		$viewData = [
			'items' => ['one', 'two', 'three'],
		];

		return $this->renderer->template($response, 'home.latte', $viewData);
	}
}
```

To make it work, create a template file in `templates/home.latte` with this content:

```latte
<ul n:if="$items">
	{foreach $items as $item}
		<li id="item-{$iterator->counter}">{$item|capitalize}</li>
	{/foreach}
</ul>
```

If everything is configured correctly you should see the following output:

```latte
One
Two
Three
```

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