Function generic_singleton::get_or_init

pub fn get_or_init<T: 'static>(init: fn() -> T) -> &'static T

Get a static reference to a generic singleton or initialize it if it doesn’t exist.

You can even call get_or_init inside the init function, although, if you’re initializing the same type, the outer call will persist. If this example confuses you, don’t worry, it’s a contrived non-sensical example that resulted from testing the safety of this library.

Example

use std::sync::Mutex;

fn generic_function<T: Copy + std::ops::Add<Output = T> + 'static>(initializer: fn() -> Mutex<T>) -> T {
    {
        let mut a = generic_singleton::get_or_init(initializer).lock().unwrap();
        let b = *a;
        *a = *a + b;
        *a
    }
}

fn main() {
    assert_eq!(generic_function(||Mutex::new(2)), 4);
    assert_eq!(generic_function(||Mutex::new(2)), 8);
    assert_eq!(generic_function(||Mutex::new(2)), 16);

    assert_eq!(generic_function(||Mutex::new(2.0)), 4.0);
    assert_eq!(generic_function(||Mutex::new(2.0)), 8.0);
    assert_eq!(generic_function(||Mutex::new(2.0)), 16.0);
}