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"); }