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Questions tagged [rust-futures]

69 questions
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Future - 'Item' and 'Error' associated types not found?

I am experimenting with Tokio, Reqwest and Actix-web and creating am API that connects to SendGrid to send simple emails. I am stuck on an error: error[E0220]: associated type `Item` not found for `std::future::Future` --> src\main.rs:20:79 …
John Watson
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Async: how to keep using the same future in a loop with select (no_std environment)?

I have two async functions: get_message and get_event. I'd like to perform an action whenever a message arrives or an event comes and do that forever in an infinite loop. The simplified setup looks like this: use futures::{future::select,…
ynoxinul
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Implement Future trait based on future available inside the struct

I'm trying to create a DelayedValue future that resolves to a value after a certain time period has elapsed. To do this I simply wanted to wrap the Sleep future from tokio crate. But I get errors relating to Pin and no matter what I do I can't seem…
John Smith
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How can I pass a reference as a parameter into an async function in Rust?

I would like something as follows. Where my async fn my_fn(arg: &str) takes a reference and does something with it. Note that my_fn must be async because my real code does async stuff. See the Playground for the example. use futures::Future; use…
Dan
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How to accept either ownerhip or mutable reference for the same method

I am making a library in Rust around a TCP protocol. And I am also trying to make it async runtime independent. I would like to make it accept ownership of an existing connection OR accept a mutable reference to it. I.e. I want to let the caller say…
boen_robot
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reusing futures::stream::Stream and modifying state of each element

I have a futures::stream::Stream which produces elements in the form <(State, impl std::fmt::Binary)> (Binary is an arbitrary placeholder for a trait I want to use): let peers = (0..10).map(move |peer| async move { let delay =…
Kevin
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Grouping rust stream items

Streams are often described as 'async iterators'. I am more used to C++ iterators which encourage you to keep the intermediate states of the iterators for re-use in algorithms. It can be difficult to see how you neatly achieve more complex iterator…
tamathews01
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How can I perform multiple concurrent requests with reqwest using a shared client reference?

I am trying to perform multiple concurrent GET requests using the reqwest library, while using a shared reference to the Client object. The idea is this will be a long-lived client, and as suggested in the docs, I would like to take advantage of the…
Lukas S.
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Is it possible to turn a rust RocksDB iterator into a `Send + 'static` stream?

I've got a small RPC network protocol I've written, and there's a server-streaming method (very similar to gRPC style server-streaming) called range. The client sends start and end keys, and the server streams the values back. I'm using the tower…
broughjt
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Idiomatic way in async/await Rust to route an input to an existing Future or a new one based on a condition

In async/await, what's the most idiomatic/efficient way to take an input buffer and, for each item, route it to an existing Future or a new one based on a condition? For example, you're running a server and each incoming packet might either be the…
John Stanford
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Rust: future factory method results in compiler error: value requires that `'1` must outlive `'2`

I want to repeat a certain user-provided function multiple times in an async context. Thus, I thought about a non-async closure that produces futures which can be consumed/awaited. A minimal reproducible example is the following: let counter =…
phip1611
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How to store a future without boxing it

I want to do the following struct Stored> { f: Option, } impl> Stored { fn store(&mut self, f: F) { let f = async {}; self.f = Some(f); } } But it gives me the…
Gabriel Machado
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How `tokio::spawn` handles the situation when the future can't be moved?

The function tokio::spawn is defined as follows: pub fn spawn(future: T) -> JoinHandle The future does not implement Copy trait, so it is moved into the function. But some futures can't be moved because it has pointers pointing to…
spockwang
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Rust lifetimes in async wrapper for sync code

I am trying to create a Stream using a camera with a blocking capture method. The blocking call is wrapped with blocking::unblock. use futures::stream; use rscam::{Camera, Config}; fn frame_stream() -> impl stream::Stream { let mut camera =…
Stonks3141
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Rust futures -- use Box::pin or pin_mut outside futures::select

I had read the usage of futures::select, but I encounter an obstacle. here is my confusion: At the part of expression in select!, we should use a type implementing Unpin and FusedFuture, but here Pin on a Unpin is no effect accoring to usage of…
sunboy_zgz
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