Rocket's State errors with "Attempted to retrieve unmanaged state" when using an explicit lifetime?

Question

When using Rocket's State with omitted lifetimes then a request to the route is handled ok:

#[post("/foo")]
pub fn foo_handler(db: State<Db>) {
    // ...
}

However, if explicit lifetimes are provided then Rocket errors on requests with Attempted to retrieve unmanaged state!:

#[post("/foo")]
pub fn foo_handler<'a>(db: State<&'a Db>) {
    // ...
}

There's either something the compiler isn't picking up here or Rocket avoids a safety check, as this compiles ok without any error or warnings. Any ideas?

I don't think those are the same signature. What does `db: State<&'static Db>` do? — Shepmaster, Apr 27 '19 at 22:50

score 1 · Accepted Answer · edited Apr 28 '19 at 12:54

1

This seems to be the way to achieve the required result:

#[post("/foo")]
pub fn foo_handler<'a>(db: State<'a, Db>) {
  // ...
}

A example helped in Rocket's State docs. I'd expect an error to be thrown for the above implementations though, as it's valid syntax.

edited Apr 28 '19 at 12:54

Shepmaster

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answered Apr 28 '19 at 12:42

Will Squire

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score 0 · Answer 2 · answered Jul 04 '20 at 01:53

I found this error resulted from failing to call unwrap() on the value I was initializing to be used in the State.

let index = load().unwrap(); // <-- without unwrap, compiled but failed on request
rocket::ignite()
  .manage(index) // normal mount and so on here
... etc ...

Rocket's State errors with "Attempted to retrieve unmanaged state" when using an explicit lifetime?

2 Answers2