Macros to make your life easier when dealing with default-initialized
arrays of Option<T> or Cell<Option<T>> for non-Copy types of T to [None, ..].
- You need an array of
[Option<T>; N]initialized to[None; N], or - You need an array of
[Cell<Option<T>>; N]initialized to[Cell::new(None); N], or - You need an array of
[RefCell<Option<T>>; N]initialized to[RefCell::new(None); N].
- Your types already implement
CopyorCloneand you don't need cells. - You require
#![forbid(unsafe_code)].
use core::cell::Cell;
use arraysetcell::ArraySetCell;
// This type does not implement Copy.
struct Complicated;
fn it_works() {
// This doesn't compile:
let arr: [Option<Complicated>; 10] = [None; 10];
// This does:
let arr = none_arr![Complicated; 10];
// [None, None, None, ...]
assert_eq!(arr.len(), 10);
for item in arr.into_iter() {
assert!(item.is_none());
}
// The created type is an array.
let arr: [Option<Complicated>; 10] = arr;
assert_eq!(arr.len(), 10);
}Likewise, arrays of Cell<Option<T>> can be created.
fn cell_works() {
let arr: [Cell<Option<Complicated>>; 10] = none_cell_arr![Complicated; 10];
let arr: [RefCell<Option<Complicated>>; 10] = none_refcell_arr![Complicated; 10];
}If you cannot have unsafe code in your project, something like the following can be used:
fn not_fun() {
let arr: [Option<Complicated>; 10] = (0..10)
.into_iter()
.map(|_| None)
.collect::<Vec<_>>()
.try_into()
.map_err(|_| "try_into failed") // Debug required otherwise
.expect("initialization failed");
}