Tags and Metadata
A tag is a piece of information that you can add to content in Yarn Spinner that adds additional context or detail about that content.
There are two places you can add tags in Yarn scripts: you can add them to nodes, and you can add them to lines. Tags aren't shown to the user; instead, they're used by your game, or by Yarn Spinner itself.
Tags in lines
Tags can be added to the end of lines and options. Tags on lines start with a hash symbol (#), and cannot contain spaces. You can add as many tags as you like to line, but they must all be on the same line in the script.
Here's an example of a line with two tags:
Accessing tags
Tags that you add to a line can be accessed from your game. The way that you access them depends on your game engine. For example, to access them in a Unity game, you use the LocalizedLine.Metadata property.
Some tags are used by Yarn Spinner itself, while all others are used by your own code, so it's up to you what content they should have, and how to handle them.
Special tags
Certain tags are used internally by Yarn Spinner, or are added for you if they don't exist.
#lastline
#lastlineThe Yarn Spinner compiler adds a #lastline tag to every line that comes just before a set of options.
For example, the following excerpt:
is treated as though it had been written as:
In a Unity game, you can use this tag in a custom Dialogue View to be notified ahead of time when the player is about to be shown options.
The #lastline tag will not be automatically added if there is any content, such as an if statement or a command, between the line and some options. In these situations, you may wish to manually add the tag yourself.
#line
#lineThe #line tag uniquely identifies a single line or option across all of your game's dialogue. This is used to identify lines for localisation. Every line's #line tag must be unique. If a line or option doesn't have a #line tag, it will be automatically added for you.
Here's an example of some Yarn script with #line tags:
For more details (including what the tag should look like), see Adding Line IDs.
Tags in nodes
Nodes can also have tags, which you can use to add labels that describe the node.
Node tags they work a bit differently than line tags: they are defined in the header with the tags key, and they don't have to begin with a hash symbol (#).
Here's an example of a node with two tags:
You can access the tags on a node via the Dialogue object's GetTagsForNode method.
Other metadata
The metadata of a line is only composed of tags. Because of this, you may find that the Yarn Spinner code and documentation refer to line tags and line metadata interchangeably.
Nodes can have other metadata in their headers. This metadata isn't exposed through the API, which means it's mostly used to store additional information for whoever is writing the Yarn dialogue or for editors to make use of.
However, currently there is one header that defines specific behavior within the Yarn Spinner compiler: the tracking header.
The tracking header
tracking headerNodes can track whether they have already been visited during the game. For this to work, the Yarn Spinner compiler needs to add some special code to the node. To avoid creating this code for nodes that don't need it, the compiler only adds this code if it finds a call to the visited() function with the node name in it.
In some cases, you may need the compiler to add this special code to a node even if no corresponding visited() call exists. To direct the compiler to do this, include the tracking header with the value of always:
Additionally, using a value of never instructs the compiler to never add this special code to the node. If you use the visited function with a node set to never use tracking, it will always return false.
For more information on visit tracking, see the documentation for Functions.
Example use cases
Tags and metadata may seem very complicated at first, and their uses may not be clear. The following example use cases explain how they can be used in your game. Keep in mind that this is not an exhaustive list of use cases.
Controlling attributes for an entire line
Yarn provides markup to let you change attributes for specific parts of a line. In case most of your attributes apply to entire lines (for example, the color of a line), it may be easier to just use tags instead.
Displaying the last line of dialogue along with options
The #lastline tag can be used to display the last line of dialogue along with any options. This is handled within your code by checking if a line has the #lastline tag, and if it does, storing it before continuing with the execution of the Yarn dialogue.
Internal workflows
Since metadata isn't shown directly to the player, you can use metadata for any internal workflows or tooling. For example, instead of tracking lines that need to be revised outside the Yarn files (which could lead to syncing problems), you could add line tags (such as #needsrevision) to the appropriate lines directly in the Yarn files, and process these lines as part of an internal tool or workflow. The Unity integration automatically generates a CSV file with all lines that contain metadata, making this super easy!
Localisation
As referenced before, the Yarn Spinner integration for Unity uses line tags to link localised dialogue lines. This is better explained in the Localization and Assets section.
Aside from that, every piece of metadata can be used by translators and adapters to help them understand how the text is being used, thus leading to better localised text.
Showing specific lines of dialogue outside a dialogue window
Some games may require that certain lines of dialogue are displayed somewhere other than the dialogue window (for example, as flavor text for an item description, or in an item that acts as a log). Instead of manually duplicating these lines (which adds overhead during development and localisation), tags can be used along with code that checks for the tags and duplicates the lines while the game is running.