Collection and Overlay Definitions often share a lot of common or generalizable configuration details. Templates allow you to define these details so they can be used across multiple definitions.
Note: The `sort_title` in these examples is wrapped in quotes because it contains a character [`!`] which has syntactic meaning in YAML files. This "quoting special characters" is a general YAML requirement, not something specific to `sort_title`.
You could keep going in this way, but there's a lot of repetition there. Both of these collections have the same `sync_mode`, `collection_order`, and `actor` settings; the other two details, `tmdb_person` and `sort_title`, depend on a value defined in the collection.
Note that we provide the template name `Actor` and the value to insert in the place of `<<person>>`. The `<<collection_name>>` is a template variable that is always available and doesn't have to be called out like `<<person>>`.
Inside a template, you can use all the Builders, Details, and [Filters](filters) attributes that you can give collections/playlists [except `template`; templates cannot be nested].
The names of template variables that you define are arbitrary. In the example above, `<<person>>` could have been `<<tvdb_person_id>>` or `<<bing>>` or anything else. The only thing that matters is that in the template definition you surround them with `<< >>` and in the collection definition you spell it correctly.
To use a template with a collection definition you use the `template` attribute. The only required attribute under `template` is `name` which must correspond exactly to the template mapping name. Any other attributes under `template` are considered template variables whose names correspond exactly with the template variable name surrounded by `<<` and `>>` in the templates. These template variables will replace any part of any value that contains the template variable name surrounded by `<<` and `>>` in the template with the specified template variable's value.
Here's the full example Actor template and two different ways to use it, as it would appear in a metadata file.
*`default` can set default values for template variables to be used if they're not specified in the call.
*`optional` can specify variables that if not specified on the template call will cause any attribute using one of those variables to be ignored in the template. You can make any template variable optional per collection by setting it to `null`.
i.e. If you have `move_prefix: The` and a collection is called `The Avengers` then `<<collection_sort>>` is replaced with `Avengers, The` instead of `The Avengers` for that collection.
* If the attribute key ends with `.not` the value must not equal the attribute value or not be in the list of attribute values.
* If the attribute key ends with `.exists` and the attribute value is `true` then the attribute key must be a given template variable and if the value is anything else then the attribute key must not be a given template variable.
* Otherwise, the value must equal the attribute value or be in the list of attribute values.
Here's an example from the [PMM Default ratings file](https://github.com/meisnate12/Plex-Meta-Manager/blob/master/defaults/overlays/ratings.yml).
summary: Action film is a genre wherein physical action takes precedence in the storytelling. The film will often have continuous motion and action including physical stunts, chases, fights, battles, and races. The story usually revolves around a hero that has a goal, but is facing incredible odds to obtain it.
summary: Comedy is a genre of film that uses humor as a driving force. The aim of a comedy film is to illicit laughter from the audience through entertaining stories and characters. Although the comedy film may take on some serious material, most have a happy ending. Comedy film has the tendency to become a hybrid sub-genre because humor can be incorporated into many other genres. Comedies are more likely than other films to fall back on the success and popularity of an individual star.
summary: Romantic Comedy is a genre that attempts to catch the viewer’s heart with the combination of love and humor. This sub-genre is light-hearted and usually places the two protagonists in humorus situation. Romantic-Comedy film revolves around a romantic ideal, such as true love. In the end, the ideal triumphs over the situation or obstacle, thus creating a happy ending.
filters:
genre: Comedy
```
Check out the example files in the [Plex Meta Manager Configs Repository](https://github.com/meisnate12/Plex-Meta-Manager-Configs/tree/master/meisnate12) for more uses and examples.
To load external templates located in another file you can use the `external_templates` attribute by specifying the path type and path of the files that will be executed. See [Path Types](../config/paths) for how to define them.
