Type System
***********

<div class=perex>

Type system is main thing for the development of robust applications. Latte brings type support to templates. To knowing what data or object type each variable is allows

- IDE to correctly autocomplete (see [integration and plugins|recipes#Editors and IDE])
- static analysis to detect errors

Two points that significantly improve the quality and convenience of development.

</div>

.[note]
The declared types are informative and Latte does not check them at this time.

How to start using types? Create a template class, eg `CatalogTemplateParameters`, representing the passed parameters:

```php
class CatalogTemplateParameters
{
	public function __construct(
		public string $langs,
		/** @var ProductEntity[] */
		public array $products,
		public Address $address,
	) {}
}

$latte->render('template.latte', new CatalogTemplateParameters(
	address: $userAddress,
	lang: $settings->getLanguage(),
	products: $entityManager->getRepository('Product')->findAll(),
));
```

Then insert the `{templateType}` tag with the full class name (including the namespace) at the beginning of the template. This defines that there are be variables `$langs` and `$products` in the template including the corresponding types.
You can also specify the types of local variables using tags [`{var}` |tags#var-default], `{varType}` and [`{define}` |template-inheritance#definitions].

Now the IDE can correctly autocomplete.

How to save work? How to write a template class or `{varType}` tags as easily as possible? Get them generated.
That is precisely what pair of tags `{templatePrint}` and `{varPrint}` do.
If you place one of these tags in a template, the code of class or template is displayed instead of the normal rendering. Then simply select and copy the code into your project.


`{templateType}`
----------------
The types of parameters passed to the template are declared using class:

```latte
{templateType MyApp\CatalogTemplateParameters}
```


`{varType}`
-----------
How to declare types of variables? For this purpose use tag `{varType}` for an existing variable, or [`{var}` |tags#var-default]:

```latte
{varType Nette\Security\User $user}
{varType string $lang}
```


`{templatePrint}`
-----------------
You can also generate this class using the `{templatePrint}` tag. If you place it at the beginning of the template, the code of class is displayed instead of the normal template. Then simply select and copy the code into your project.


`{varPrint}`
------------
The `{varPrint}` tag saves you time. If you place it in a template, the list of `{varType}` tags is displayed instead of the normal rendering. Then simply select and copy the code into your template.

The `{varPrint}` lists local variables that are not template parameters. If you want to list all variables, use `{varPrint all}`.