Struct FeedbackStream 

pub struct FeedbackStream<'a, A: RosAction, const GOAL_BUF: usize = { crate::config::DEFAULT_RX_BUF_SIZE }, const RESULT_BUF: usize = { crate::config::DEFAULT_RX_BUF_SIZE }, const FEEDBACK_BUF: usize = { crate::config::DEFAULT_RX_BUF_SIZE }> { /* private fields */ }

A stream of feedback messages from an action server.

Created by ActionClient::feedback_stream(). Receives feedback for all active goals. The stream never self-terminates — use combinators like take_while or break to stop.

Three access modes:

• Async (Stream): Enable the stream feature for futures_core::Stream + StreamExt combinators
• Async (no deps): Use next() in while let loops (always available)
• Sync: Use wait_next() which drives the executor internally

Implementations

impl<A: RosAction, const GOAL_BUF: usize, const RESULT_BUF: usize, const FEEDBACK_BUF: usize> FeedbackStream<'_, A, GOAL_BUF, RESULT_BUF, FEEDBACK_BUF>

pub async fn recv(&mut self) -> Option<Result<(GoalId, A::Feedback), NodeError>>

Async: wait for the next feedback message (no futures dependency needed).

Requires a background task running executor.spin_async() to drive I/O. Returns None only on error.

When the stream feature is enabled, prefer StreamExt::next() or TryStreamExt::try_next() for combinator support.

Example

let mut stream = client.feedback_stream();
while let Some(result) = stream.recv().await {
    let (goal_id, feedback) = result?;
    // process feedback...
}

pub fn wait_next( &mut self, executor: &mut Executor, timeout: Duration, ) -> Result<Option<(GoalId, A::Feedback)>, NodeError>

Sync: wait for the next feedback message, spinning the executor.

Returns Ok(Some(feedback)) if a message arrives within timeout_ms, or Ok(None) on timeout. Unlike Promise::wait(), timeout is not an error — the caller typically retries in a loop.