Attribute Macro magnus::init

#[init]

Mark a function as the ‘init’ function to be run for a library when it is required by Ruby code.

The init function is used to define your Ruby modules & classes, bind functions as Ruby methods, etc.

Examples

fn distance(a: (f64, f64), b: (f64, f64)) -> f64 {
    ((b.0 - a.0).powi(2) + (b.1 - a.1).powi(2)).sqrt()
}

#[magnus::init]
fn init() {
    magnus::define_global_function("distance", magnus::function!(distance, 2));
}

The init function can also return Result<(), magnus::Error>.

use magnus::{define_module, function, method, prelude::*, Error};

#[magnus::wrap(class = "Euclid::Point", free_immediatly, size)]
struct Point {
    x: isize,
    y: isize,
}

impl Point {
    fn new(x: isize, y: isize) -> Self {
        Self { x, y }
    }

    fn x(&self) -> isize {
        self.x
    }

    fn y(&self) -> isize {
        self.y
    }
}

#[magnus::init]
fn init() -> Result<(), Error> {
    let module = define_module("Euclid")?;
    let class = module.define_class("Point", Default::default())?;
    class.define_singleton_method("new", function!(Point::new, 2));
    class.define_method("x", method!(Point::x, 0));
    class.define_method("y", method!(Point::y, 0));
    Ok(())
}