Variables

Throughout a story it can be useful to introduce variables, which can be declared and used in the story text. This makes it easy to keep a story consistent and track a story state.

Declaring variables

Global variables can be declared in the script using the VAR keyword. They must be declared in the preamble: before the first knot.

#![allow(unused)]
fn main() {
extern crate inkling;
use inkling::{read_story_from_string, Variable};
let content = r#"

VAR a_float = 1.0
VAR a_int = 2
VAR a_bool = false
VAR a_string = "A String"
VAR a_destination = "-> stairwell"

"#;
let story = read_story_from_string(content).unwrap();
assert_eq!(story.get_variable("a_float").unwrap(), Variable::Float(1.0));
assert_eq!(story.get_variable("a_int").unwrap(), Variable::Int(2));
assert_eq!(story.get_variable("a_bool").unwrap(), Variable::Bool(false));
assert_eq!(story.get_variable("a_string").unwrap(), Variable::String("A String".to_string()));
assert!(story.get_variable("a_destination").is_some());
}

As shown in this example, the variable type is automatically assigned from the given value. Once assigned, a variable’s type cannot be changed.

Using variables in text

Variables can be inserted into text by enclosing them in curly braces.

#![allow(unused)]
fn main() {
extern crate inkling;
use inkling::{read_story_from_string, Variable};
let content = r#"

VAR time = 11
VAR moon = "gloomy"

The time was {time}. A {moon} moon illuminated the room.

"#;
let mut story = read_story_from_string(content).unwrap();
let mut buffer = Vec::new();
story.resume(&mut buffer).unwrap();
assert_eq!(buffer[0].text, "The time was 11. A gloomy moon illuminated the room.\n");
}

Variable assignment

It is not currently possible to assign variables in the script. Use Story::set_variable.

Constant variables

Constant variables, whose values cannot be changed, are declared using the CONST keyword.

#![allow(unused)]
fn main() {
extern crate inkling;
use inkling::{read_story_from_string, Variable};
let content = r#"

CONST name = "d'Artagnan" // Constant variable, cannot be modified
VAR rank = "Capitaine"    // Non-constant variable, can be changed

"#;
let mut story = read_story_from_string(content).unwrap();
assert_eq!(story.get_variable("name").unwrap(), Variable::from("d'Artagnan"));
assert!(story.set_variable("name", "Aramis").is_err());
}

Variable mathematics

Variable comparisons