3 unstable releases
0.2.1 | Jul 25, 2024 |
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0.2.0 | Jul 18, 2024 |
0.1.0 | Jul 17, 2024 |
#904 in Rust patterns
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lazyinit
Initialize a static value lazily.
Unlike lazy_static
, which hardcodes the initialization routine in a macro, you can initialize the value in any way.
Examples
use lazyinit::LazyInit;
static VALUE: LazyInit<u32> = LazyInit::new();
assert!(!VALUE.is_inited());
// println!("{}", *VALUE); // panic: use uninitialized value
assert_eq!(VALUE.get(), None);
VALUE.init_once(233);
// VALUE.init_once(666); // panic: already initialized
assert!(VALUE.is_inited());
assert_eq!(*VALUE, 233);
assert_eq!(VALUE.get(), Some(&233));
Only one of the multiple initializations can succeed:
use lazyinit::LazyInit;
use std::time::Duration;
const N: usize = 16;
static VALUE: LazyInit<usize> = LazyInit::new();
let threads = (0..N)
.map(|i| {
std::thread::spawn(move || {
std::thread::sleep(Duration::from_millis(10));
VALUE.call_once(|| i)
})
})
.collect::<Vec<_>>();
let mut ok = 0;
for (i, thread) in threads.into_iter().enumerate() {
if thread.join().unwrap().is_some() {
ok += 1;
assert_eq!(*VALUE, i);
}
}
assert_eq!(ok, 1);