Encapsulating an object and a reference that uses its lifetime

Question

I’m working with a Rust library that uses references to provide access to child objects (the library is zip, but I’ve had this come up in other contexts as well). Its usage pattern is as follows:

Call Foo::new(arg1: A) -> Foo to get a Foo.
Call Foo.member<'a>(&'a self) -> &'a Bar<'a> to get a Bar, and use it.

Now, I want to write a convenience function that takes arg1 and returns Bar, or an object encapsulating Bar (it’s easy to implement and delegate the relevant traits of Bar.

This seems to be a prime use case for the nonexistent 'self lifetime.

Is there a good, safe, Rustic way to do this encapsulation? The best I’ve been able to come up with uses a bit of unsafe: put Foo in a box, leak it, save its pointer (along with the Bar reference) in an encapsulating struct, and implement Drop to re-box and drop Foo.

are these valid single quotes, or is this a display shenanigan? — Félix Adriyel Gagnon-Grenier, May 14 '21 at 14:32
It is not clear to me what the *convenience function* is and what is its relation with `Foo`. — Netwave, May 14 '21 at 16:35
This sounds like a classic self-referential struct: https://stackoverflow.com/questions/32300132/why-cant-i-store-a-value-and-a-reference-to-that-value-in-the-same-struct — kmdreko, May 14 '21 at 18:27
@FélixGagnon-Grenier No, those are U+2018. It hurts my eyes. — mkayaalp, May 14 '21 at 22:59
@netwave I have cleaned up the arguments to try to make it clearer. — Michael Ekstrand, May 15 '21 at 04:51
From some of the answers to the question linked by @kmdreko, the [`owning_ref`](https://docs.rs/owning_ref/) package seems to be a good encapsulated solution to this problem. Under the hood, it uses raw pointers, but wraps this up in a safe API. — Michael Ekstrand, May 15 '21 at 16:00

Encapsulating an object and a reference that uses its lifetime

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