this post was submitted on 08 Jul 2023
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What's the Rust way of storing fetched data from runtime for later use in the program? (programming.dev)
submitted 1 year ago by [email protected] to c/[email protected]
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My program is small enough that in TS/JS I'd normally just store the data in some global variable to be access from whatever elsewhere in the app. But with Rust from what I can tell this doesn't seem to be a common practice. How should i handle this?

More specifically, I need to:

  1. program start, fetch data from my db (DONE)
  2. store this data somehow somewhere
  3. access said data (for read only in this use case)

Thanks for any insights here!

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[–] [email protected] 11 points 1 year ago (1 children)

I would consider just passing along the data directly to the functions that need access to it, rather than storing in a global state. If passing each piece of data along as separate parameters is a bit much, you can always create struct Context { ... } which keeps tracks of whatever you need and pass that around.

Nothing wrong with using OnceCell as @[email protected] suggested, but I've found that passing it as an argument feels a bit better.

[–] [email protected] 4 points 1 year ago (1 children)

I might not need global state, the more I think about it. I'll start with passing a struct and see where that gets me, thanks!

[–] [email protected] 3 points 1 year ago

Using OnceCell for inviting some static resource, like a regex expression. Or for storing something like a internal cache for a function is ok. But I would avoid using it to hold a application wide state that anything can drop in and modify. Passing around application state where it is needed is generally much better and far easier to test things with.