if statementsIn addition to storing information, variables are useful for controlling what's shown to the player. To do this, you use if statements.
An if statement allows you to control whether a collection of content is shown or not. When you write an if statement, you provide an expression, which is checked; if that expression evaluates to a "true" value, then all of the content in between the <<if>> and <<endif>> statements are run.
For example, consider the following code:
This example will set a variable, $gold_amount, to 5. It will then show the line "I'd like to buy a pie!", and before it continues, it will check to see if $gold_amount is less than 10. If that's the case (which it will be!), the line "Well, you can't afford one!" will run.
elseif and elseYou can use the elseif and else statements to handle different situations in an if statement.
An elseif statement has an expression that gets checked if the if statement, or any previous elseif statements, don't run.
An else statement doesn't have an expression, and runs
For example:
This script will show different lines depending on the value of $gold_amount. The checks are done from top to bottom, which means that in order for an elseif or else to run, all of the checks above it have to have failed.
If it's less than 10, the line "Well, you can't afford one!" will run.
Otherwise, if it's less than 15, the line "You can almost afford one!" will run.
Otherwise, the line "Here you go!" will run.
The expression used in an if and elseif statement must result in a boolean value (that is, true or false.) For exame,<<if 1>> isn't allowed, but <<if 1 == 1>> is.
When presenting options to the player, you may want to make some options not available. You can do this by adding a condition to the option.
For example, if you have a variable that tracks your player's "reputation points", called $reputation, you might want to make certain options only available if the value of $reputation is high enough.
Conditions on options are done by adding an if statement to the end of the option. They look like this:
When Yarn Spinner runs this collection of options, it will check the expression inside the if statement. If the expression is false, then the option will be marked as unavailable.
Yarn Spinner always delivers every option in an option group to the game; it's up to the game to decide what to do with options that are marked as unavailable.
For example, an unavailable option might be shown to the user, but not selectable, so that the user can see that they could have been able to say that if circumstances had been different.
Now that you know how to work with nodes, lines, options and variables, there's one last part of the Yarn language to learn about: commands.