153. OnceCell — Memoize Through &self Without Wrapping in RefCell

Thu, 21 May 2026 09:00:00 +0100

You have a parse(&self) -> &Heavy accessor that needs to compute once and cache. &self rules out a plain field assignment. Cell needs Copy. RefCell won’t lend the inside out past .borrow(). OnceCell<T> is the missing piece — write-once, &self API, hands back a real &T that lives as long as the cell.

Oncecell on rustbites

153. OnceCell — Memoize Through &self Without Wrapping in RefCell