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Using OnceCell with Regex (for reading only) (lemmyrs.org)

submitted 1 year ago by [email protected] to c/[email protected]

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I've been using lazy_static until now but was trying to migrate to OnceCell. It seems I can't have a OnceCell even though I'm never calling mutable methods on the regex. I'm not even using multiple threads.

The error I'm getting is:

Any way to solve this or do I have to use OnceLock / continue using lazy_static? I don't want to add the overhead of using OnceLock if not necessary.

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[–] [email protected] 2 points 1 year ago (1 children)

First of all, thank you for this very elaborate answer. So that means OnceCell can never be used in a static but only as local variable / member variable? I see, that makes sense and also reduces its use cases by a lot of what I initially thought. But your example makes sense and the name/package also suggest it's not thread-safe in itself, I had just wrongly assumed OnceCell was meant to be used in static contexts.

Thanks!

[–] [email protected] 5 points 1 year ago

Yeah, it doesn't help that in the once_cell crate, the thread-safe version was also called OnceCell; you had to choose between once_cell::sync::OnceCell and once_cell::unsync::OnceCell. But when it was added to the standard library, once_cell::sync::OnceCell was renamed to OnceLock to make them easier distinguishable. So