The Yarn language is a full programming language, which means it has support for writing code that let you control how the dialogue in your game works. In this section, you'll learn how to use variables to control your dialogue.
Variables store information. Variables can store one of three types of information: numbers, strings, and booleans.
| Type | Possible Values | Examples |
|---|---|---|
Every variable has a name. In Yarn Spinner, all variable names start with a dollar sign ($).
You put information into a variable by using the <<set>> command. For example, the following code puts a string, "Hello, Yarn!", into a variable called $greeting:
As with node titles, variable names must not contain spaces. They must be made up of only letters, numbers and underscores, and the first character must be a letter.
Each variable can only store one type of value. Variables can change their value at any time, but they can never change their type.
For example, the following code will work:
This works because while the value of each of the variable changes, the type doesn't. However, the following code will not work:
Starting with Yarn Spinner 2.0, variables are never null. All variables are required to have a value.
You can work with the values inside variables. For example, numbers can be multiplied, strings can be added together, and boolean values can have logical operations (like and and or) applied to them. When values are used together like this, it's called an expression.
An expression needs to be a single type. You can't work with values of different types in a single expression. For example, the following code will not work:
Yarn Spinner provides built-in functions for converting between certain types:
The string function converts values of any type into a string.
The number function converts values of any type into a number (if it can be interpreted as one.)
The bool function converts values of any type into a boolean value (if it can be interpreted as one.)
To show the contents of a variable, you put it inside braces ({ }) inside a line. The value of that variable will appear in its place.
For example:
Yarn Spinner doesn’t manage the storage of information in variables itself. Instead, your game provides a variable storage object to Yarn Spinner before you start running dialogue.
When Yarn Spinner needs to know the value of a variable, it will ask the variable storage object you’ve given it. When Yarn Spinner wants to set the value of a variable, it will provide the value and the name of the variable. In this way, your game has control over how data is stored.
The specifics of how variables need to be stored will vary depending on what game engine you're using Yarn Spinner in. To learn more about variable storage in Unity, see Variable Storage.
Number
Any whole or decimal number
1, 2.5, 3468900, -500
String
Any sequence of letters, numbers and other characters, enclosed in quotes.
"Hello", "✓", "A whole sentence."
Boolean
Either the value true or the value false.
true, false