Trait TryStreamExt 

pub trait TryStreamExt: TryStream {
    // Provided methods
    fn err_into<E>(self) -> ErrInto<Self, E>
       where Self: Sized,
             Self::Error: Into<E> { ... }
    fn map_ok<V, F>(self, f: F) -> MapOk<Self, V, F>
       where Self: TryStream + Unpin + Sized,
             F: FnMut(Self::Ok) -> V { ... }
    fn map_err<E, F>(self, f: F) -> MapErr<Self, E, F>
       where Self: TryStream + Unpin + Sized,
             E: Error,
             F: FnMut(Self::Error) -> E { ... }
    fn and_then<Fut, F>(self, f: F) -> AndThen<Self, Fut, F>
       where F: FnMut(Self::Ok) -> Fut,
             Fut: TryFuture<Error = Self::Error>,
             Self: Sized { ... }
    fn or_else<Fut, F>(self, f: F) -> OrElse<Self, Fut, F>
       where F: FnMut(Self::Error) -> Fut,
             Fut: TryFuture<Ok = Self::Ok>,
             Self: Sized { ... }
    fn try_forward<S>(self, sink: S) -> TryForward<Self, S> 
       where S: Sink<Self::Ok, Error = Self::Error>,
             Self: Sized { ... }
    fn inspect_ok<F>(self, f: F) -> InspectOk<Self, F>
       where F: FnMut(&Self::Ok),
             Self: Sized { ... }
    fn inspect_err<F>(self, f: F) -> InspectErr<Self, F>
       where F: FnMut(&Self::Error),
             Self: Sized { ... }
    fn into_stream(self) -> IntoStream<Self>
       where Self: Sized { ... }
    fn try_next(&mut self) -> TryNext<'_, Self> 
       where Self: Unpin { ... }
    fn try_skip_while<Fut, F>(self, f: F) -> TrySkipWhile<Self, Fut, F>
       where F: FnMut(&Self::Ok) -> Fut,
             Fut: TryFuture<Ok = bool, Error = Self::Error>,
             Self: Sized { ... }
    fn try_take_while<Fut, F>(self, f: F) -> TryTakeWhile<Self, Fut, F>
       where F: FnMut(&Self::Ok) -> Fut,
             Fut: TryFuture<Ok = bool, Error = Self::Error>,
             Self: Sized { ... }
    fn try_collect<C: Default + Extend<Self::Ok>>(self) -> TryCollect<Self, C> 
       where Self: Sized { ... }
    fn try_chunks(self, capacity: usize) -> TryChunks<Self>
       where <IntoFuseStream<Self> as Stream>::Item: Debug,
             Self: Sized { ... }
    fn try_ready_chunks(self, capacity: usize) -> TryReadyChunks<Self>
       where Self: Sized { ... }
    fn try_filter<Fut, F>(self, f: F) -> TryFilter<Self, Fut, F>
       where Fut: Future<Output = bool>,
             F: FnMut(&Self::Ok) -> Fut,
             Self: Sized { ... }
    fn try_filter_map<Fut, F, T>(self, f: F) -> TryFilterMap<Self, Fut, F>
       where Fut: TryFuture<Ok = Option<T>, Error = Self::Error>,
             F: FnMut(Self::Ok) -> Fut,
             Self: Sized { ... }
    fn try_flatten_unordered(
        self,
        limit: impl Into<Option<usize>>,
    ) -> TryFlattenUnordered<Self>
       where Self: Sized,
             Self::Ok: TryStream + Unpin,
             <Self::Ok as TryStream>::Error: From<Self::Error> { ... }
    fn try_flatten(self) -> TryFlatten<Self>
       where Self::Ok: TryStream,
             <Self::Ok as TryStream>::Error: From<Self::Error>,
             Self: Sized { ... }
    fn try_concat(self) -> TryConcat<Self> 
       where Self: Sized,
             Self::Ok: Extend<<<Self as TryStream>::Ok as IntoIterator>::Item> + IntoIterator + Default { ... }
    fn try_buffer_unordered(
        self,
        n: impl Into<Option<usize>>,
    ) -> TryBufferUnordered<Self>
       where Self::Ok: TryFuture<Error = Self::Error>,
             Self: Sized { ... }
    fn try_buffered(self, n: impl Into<Option<usize>>) -> TryBuffered<Self>
       where Self::Ok: TryFuture<Error = Self::Error>,
             Self: Sized { ... }
    fn try_poll_next_unpin(
        &mut self,
        cx: &mut Context<'_>,
    ) -> Poll<Option<Result<Self::Ok, Self::Error>>>
       where Self: Unpin { ... }
    fn try_all<Fut, F>(self, f: F) -> TryAll<Self, Fut, F> 
       where Self: Sized,
             F: FnMut(Self::Ok) -> Fut,
             Fut: Future<Output = bool> { ... }
    fn try_any<Fut, F>(self, f: F) -> TryAny<Self, Fut, F> 
       where Self: Sized,
             F: FnMut(Self::Ok) -> Fut,
             Fut: Future<Output = bool> { ... }
}

Adapters specific to Result-returning streams

Provided Methods

fn err_into<E>(self) -> ErrInto<Self, E>

where Self: Sized, Self::Error: Into<E>,

Wraps the current stream in a new stream which converts the error type into the one provided.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

#[tokio::main]
async fn main() {
let stream =
    tokio_stream::iter(vec![Ok::<(), i32>(()), Err::<(), i32>(5)])
        .err_into::<i64>();

let collected =  stream.into_stream().collect::<Vec<_>>().await;
assert_eq!(collected, vec![Ok(()), Err(5i64)]);
}

fn map_ok<V, F>(self, f: F) -> MapOk<Self, V, F>

where Self: TryStream + Unpin + Sized, F: FnMut(Self::Ok) -> V,

Wraps the current stream in a new stream which maps the success value using the provided closure.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

#[tokio::main]
async fn main() {
let stream =
    tokio_stream::iter(vec![Ok::<i32, i32>(5), Err::<i32, i32>(0)])
        .map_ok(|x| x + 2);

let out =  stream.into_stream().collect::<Vec<_>>().await;
assert_eq!(out, vec![Ok(7), Err(0)]);
}

fn map_err<E, F>(self, f: F) -> MapErr<Self, E, F>

where Self: TryStream + Unpin + Sized, E: Error, F: FnMut(Self::Error) -> E,

Wraps the current stream in a new stream which maps the error value using the provided closure.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

#[derive(Debug)]
struct MyErr(String);
impl core::fmt::Display for MyErr { fn fmt(&self, f:&mut core::fmt::Formatter<'_>)->core::fmt::Result{ self.0.fmt(f)} }
impl core::error::Error for MyErr {}

let stream =
    tokio_stream::iter(vec![Ok::<i32, i32>(5), Err::<i32, i32>(0)])
        .map_err(|x| MyErr(format!("e{}", x)));

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
let out = rt.block_on(async { stream.into_stream().collect::<Vec<_>>().await });
assert_eq!(format!("{:?}", out), format!("{:?}", vec![Ok(5), Err(MyErr(String::from("e0")))]));

fn and_then<Fut, F>(self, f: F) -> AndThen<Self, Fut, F>

where F: FnMut(Self::Ok) -> Fut, Fut: TryFuture<Error = Self::Error>, Self: Sized,

Chain on a computation for when a value is ready, passing the successful results to the provided closure f.

This function can be used to run a unit of work when the next successful value on a stream is ready. The closure provided will be yielded a value when ready, and the returned future will then be run to completion to produce the next value on this stream.

Any errors produced by this stream will not be passed to the closure, and will be passed through.

The returned value of the closure must implement the TryFuture trait and can represent some more work to be done before the composed stream is finished.

Note that this function consumes the receiving stream and returns a wrapped version of it.

To process the entire stream and return a single future representing success or error, use try_for_each instead.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let stream = tokio_stream::iter(vec![Ok::<i32, ()>(1), Ok(2)])
        .and_then(|result| async move {
            Ok(if result % 2 == 0 { Some(result) } else { None })
        });

    let out = stream.into_stream().collect::<Vec<_>>().await;
    assert_eq!(out, vec![Ok(None), Ok(Some(2))]);
});

fn or_else<Fut, F>(self, f: F) -> OrElse<Self, Fut, F>

where F: FnMut(Self::Error) -> Fut, Fut: TryFuture<Ok = Self::Ok>, Self: Sized,

Chain on a computation for when an error happens, passing the erroneous result to the provided closure f.

This function can be used to run a unit of work and attempt to recover from an error if one happens. The closure provided will be yielded an error when one appears, and the returned future will then be run to completion to produce the next value on this stream.

Any successful values produced by this stream will not be passed to the closure, and will be passed through.

The returned value of the closure must implement the TryFuture trait and can represent some more work to be done before the composed stream is finished.

Note that this function consumes the receiving stream and returns a wrapped version of it.

fn try_forward<S>(self, sink: S) -> TryForward<Self, S>

where S: Sink<Self::Ok, Error = Self::Error>, Self: Sized,

A future that completes after the given stream has been fully processed into the sink and the sink has been flushed and closed.

This future will drive the stream to keep producing items until it is exhausted, sending each item to the sink. It will complete once the stream is exhausted, the sink has received and flushed all items, and the sink is closed. Note that neither the original stream nor provided sink will be output by this future. Pass the sink by Pin<&mut S> (for example, via try_forward(&mut sink) inside an async fn/block) in order to preserve access to the Sink. If the stream produces an error, that error will be returned by this future without flushing/closing the sink.

fn inspect_ok<F>(self, f: F) -> InspectOk<Self, F>

where F: FnMut(&Self::Ok), Self: Sized,

Do something with the success value of this stream, afterwards passing it on.

This is similar to the StreamExt::inspect method where it allows easily inspecting the success value as it passes through the stream, for example to debug what’s going on.

fn inspect_err<F>(self, f: F) -> InspectErr<Self, F>

where F: FnMut(&Self::Error), Self: Sized,

Do something with the error value of this stream, afterwards passing it on.

This is similar to the StreamExt::inspect method where it allows easily inspecting the error value as it passes through the stream, for example to debug what’s going on.

fn into_stream(self) -> IntoStream<Self>

where Self: Sized,

Wraps a TryStream into a type that implements Stream

TryStreams currently do not implement the Stream trait because of limitations of the compiler.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::{TryStream, TryStreamExt};

type T = i32;
type E = ();

fn make_try_stream() -> impl TryStream<Ok = T, Error = E> {
    tokio_stream::iter(vec![Ok::<T, E>(1), Ok(2), Err(())])
}

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let out = make_try_stream().into_stream().collect::<Vec<_>>().await;
    assert_eq!(out, vec![Ok(1), Ok(2), Err(())]);
});

fn try_next(&mut self) -> TryNext<'_, Self>

where Self: Unpin,

Creates a future that attempts to resolve the next item in the stream. If an error is encountered before the next item, the error is returned instead.

This is similar to the Stream::next combinator, but returns a Result<Option<T>, E> rather than an Option<Result<T, E>>, making for easy use with the ? operator.

Examples

use tokio_stream_util::TryStreamExt;

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let mut stream = tokio_stream::iter(vec![Ok::<(), ()>(()), Err::<(), ()>(())]);
    assert_eq!(stream.try_next().await, Ok(Some(())));
});

fn try_skip_while<Fut, F>(self, f: F) -> TrySkipWhile<Self, Fut, F>

where F: FnMut(&Self::Ok) -> Fut, Fut: TryFuture<Ok = bool, Error = Self::Error>, Self: Sized,

Skip elements on this stream while the provided asynchronous predicate resolves to true.

This function is similar to StreamExt::skip_while but exits early if an error occurs.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let stream = tokio_stream::iter(vec![Ok::<i32, i32>(1), Ok(3), Ok(2)])
        .try_skip_while(|x| {
            let v = *x;
            async move { Ok(v < 3) }
        });

    let out = stream.into_stream().collect::<Vec<_>>().await;
    assert_eq!(out, vec![Ok(3), Ok(2)]);
});

fn try_take_while<Fut, F>(self, f: F) -> TryTakeWhile<Self, Fut, F>

where F: FnMut(&Self::Ok) -> Fut, Fut: TryFuture<Ok = bool, Error = Self::Error>, Self: Sized,

Take elements on this stream while the provided asynchronous predicate resolves to true.

This function is similar to StreamExt::take_while but exits early if an error occurs.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let stream = tokio_stream::iter(vec![Ok::<i32, i32>(1), Ok(2), Ok(3), Ok(2)])
        .try_take_while(|x| {
            let v = *x;
            async move { Ok(v < 3) }
        });

    let out = stream.into_stream().collect::<Vec<_>>().await;
    assert_eq!(out, vec![Ok(1), Ok(2)]);
});

fn try_collect<C: Default + Extend<Self::Ok>>(self) -> TryCollect<Self, C>

where Self: Sized,

Attempt to transform a stream into a collection, returning a future representing the result of that computation.

This combinator will collect all successful results of this stream and collect them into the specified collection type. If an error happens then all collected elements will be dropped and the error will be returned.

The returned future will be resolved when the stream terminates.

Examples

use tokio_stream_util::TryStreamExt;

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let future = tokio_stream::iter(vec![Ok::<i32, i32>(1), Ok(2), Err(3)])
        .try_collect::<Vec<_>>();

    assert_eq!(future.await, Err(3));
});

fn try_chunks(self, capacity: usize) -> TryChunks<Self>

where <IntoFuseStream<Self> as Stream>::Item: Debug, Self: Sized,

An adaptor for chunking up successful items of the stream inside a vector.

This combinator will attempt to pull successful items from this stream and buffer them into a local vector. At most capacity items will get buffered before they’re yielded from the returned stream.

Note that the vectors returned from this iterator may not always have capacity elements. If the underlying stream ended and only a partial vector was created, it’ll be returned. Additionally if an error happens from the underlying stream then the currently buffered items will be yielded.

This method is only available when the std or alloc feature of this library is activated, and it is activated by default.

This function is similar to StreamExt::chunks but exits early if an error occurs.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;
use tokio_stream_util::try_stream::TryChunksError;

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let stream = tokio_stream::iter(vec![
        Ok::<i32, i32>(1), Ok(2), Ok(3), Err(4), Ok(5), Ok(6)
    ]).try_chunks(2);

    let out = stream.into_stream().collect::<Vec<_>>().await;
    assert_eq!(out, vec![
        Ok(vec![1, 2]),
        Ok(vec![3]),
        Err(TryChunksError::<i32, i32>(vec![], 4)),
        Ok(vec![5, 6]),
    ]);
});

Panics

This method will panic if capacity is zero.

fn try_ready_chunks(self, capacity: usize) -> TryReadyChunks<Self>

where Self: Sized,

An adaptor for chunking up successful, ready items of the stream inside a vector.

This combinator will attempt to pull successful items from this stream and buffer them into a local vector. At most capacity items will get buffered before they’re yielded from the returned stream. If the underlying stream returns Poll::Pending, and the collected chunk is not empty, it will be immediately returned.

Note that the vectors returned from this iterator may not always have capacity elements. If the underlying stream ended and only a partial vector was created, it’ll be returned. Additionally if an error happens from the underlying stream then the currently buffered items will be yielded.

This method is only available when the std or alloc feature of this library is activated, and it is activated by default.

This function is similar to StreamExt::ready_chunks but exits early if an error occurs.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;
use tokio_stream_util::try_stream::TryReadyChunksError;

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let stream = tokio_stream::iter(vec![
        Ok::<i32, i32>(1), Ok(2), Ok(3), Err(4), Ok(5), Ok(6)
    ]).try_ready_chunks(2);

    let out = stream.into_stream().collect::<Vec<_>>().await;
    assert_eq!(out, vec![
        Ok(vec![1, 2]),
        Ok(vec![3]),
        Err(TryReadyChunksError::<i32, i32>(vec![], 4)),
        Ok(vec![5, 6]),
    ]);
});

Panics

This method will panic if capacity is zero.

fn try_filter<Fut, F>(self, f: F) -> TryFilter<Self, Fut, F>

where Fut: Future<Output = bool>, F: FnMut(&Self::Ok) -> Fut, Self: Sized,

Attempt to filter the values produced by this stream according to the provided asynchronous closure.

As values of this stream are made available, the provided predicate f will be run on them. If the predicate returns a Future which resolves to true, then the stream will yield the value, but if the predicate return a Future which resolves to false, then the value will be discarded and the next value will be produced.

All errors are passed through without filtering in this combinator.

Note that this function consumes the stream passed into it and returns a wrapped version of it, similar to the existing filter methods in the standard library.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let events = tokio_stream::iter(vec![Ok::<i32, &str>(1), Ok(2), Ok(3), Err("error")])
        .try_filter(|x| {
            let v = *x;
            async move { v >= 2 }
        });

    let out = events.into_stream().collect::<Vec<_>>().await;
    assert_eq!(out, vec![Ok(2), Ok(3), Err("error")]);
});

fn try_filter_map<Fut, F, T>(self, f: F) -> TryFilterMap<Self, Fut, F>

where Fut: TryFuture<Ok = Option<T>, Error = Self::Error>, F: FnMut(Self::Ok) -> Fut, Self: Sized,

Attempt to filter the values produced by this stream while simultaneously mapping them to a different type according to the provided asynchronous closure.

As values of this stream are made available, the provided function will be run on them. If the future returned by the predicate f resolves to Some(item) then the stream will yield the value item, but if it resolves to None then the next value will be produced.

All errors are passed through without filtering in this combinator.

Note that this function consumes the stream passed into it and returns a wrapped version of it, similar to the existing filter_map methods in the standard library.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let halves = tokio_stream::iter(vec![Ok::<i32, &str>(1), Ok(6), Err("error")])
        .try_filter_map(|x| async move {
            let ret = if x % 2 == 0 { Some(x / 2) } else { None };
            Ok(ret)
        });

    let out = halves.into_stream().collect::<Vec<_>>().await;
    assert_eq!(out, vec![Ok(3), Err("error")]);
});

fn try_flatten_unordered( self, limit: impl Into<Option<usize>>, ) -> TryFlattenUnordered<Self>

where Self: Sized, Self::Ok: TryStream + Unpin, <Self::Ok as TryStream>::Error: From<Self::Error>,

Flattens a stream of streams into just one continuous stream. Produced streams will be polled concurrently and any errors will be passed through without looking at them. If the underlying base stream returns an error, it will be immediately propagated.

The only argument is an optional limit on the number of concurrently polled streams. If this limit is not None, no more than limit streams will be polled at the same time. The limit argument is of type Into<Option<usize>>, and so can be provided as either None, Some(10), or just 10. Note: a limit of zero is interpreted as no limit at all, and will have the same result as passing in None.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let inner1 = tokio_stream::iter(vec![Ok::<i32, i32>(1), Ok(2)]);
    let inner2 = tokio_stream::iter(vec![Ok::<i32, i32>(3), Ok(4)]);
    let base = tokio_stream::iter(vec![Ok::<_, i32>(inner1), Ok::<_, i32>(inner2)]);
    let stream = base.try_flatten_unordered(None);

    let mut out = stream.into_stream().collect::<Vec<_>>().await;
    out.sort_by_key(|r| r.clone().unwrap_or_default());
    assert_eq!(out, vec![Ok(1), Ok(2), Ok(3), Ok(4)]);
});

fn try_flatten(self) -> TryFlatten<Self>

where Self::Ok: TryStream, <Self::Ok as TryStream>::Error: From<Self::Error>, Self: Sized,

Flattens a stream of streams into just one continuous stream.

If this stream’s elements are themselves streams then this combinator will flatten out the entire stream to one long chain of elements. Any errors are passed through without looking at them, but otherwise each individual stream will get exhausted before moving on to the next.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let inner1 = tokio_stream::iter(vec![Ok::<i32, i32>(1), Ok(2)]);
    let inner2 = tokio_stream::iter(vec![Ok::<i32, i32>(3), Ok(4)]);
    let base = tokio_stream::iter(vec![Ok::<_, i32>(inner1), Ok::<_, i32>(inner2)]);
    let stream = base.try_flatten();

    let out = stream.into_stream().collect::<Vec<_>>().await;
    assert_eq!(out, vec![Ok(1), Ok(2), Ok(3), Ok(4)]);
});

fn try_concat(self) -> TryConcat<Self>

where Self: Sized, Self::Ok: Extend<<<Self as TryStream>::Ok as IntoIterator>::Item> + IntoIterator + Default,

Attempt to concatenate all items of a stream into a single extendable destination, returning a future representing the end result.

This combinator will extend the first item with the contents of all the subsequent successful results of the stream. If the stream is empty, the default value will be returned.

Works with all collections that implement the Extend trait.

This method is similar to concat, but will exit early if an error is encountered in the stream.

Examples

use tokio_stream_util::TryStreamExt;

#[tokio::main]
async fn main() {
    let fut = tokio_stream::iter(vec![
        Ok::<Vec<i32>, ()>(vec![1, 2, 3]),
        Ok(vec![4, 5, 6]),
        Ok(vec![7, 8, 9]),
    ]).try_concat();

    assert_eq!(fut.await, Ok(vec![1, 2, 3, 4, 5, 6, 7, 8, 9]));
}

fn try_buffer_unordered( self, n: impl Into<Option<usize>>, ) -> TryBufferUnordered<Self>

where Self::Ok: TryFuture<Error = Self::Error>, Self: Sized,

Attempt to execute several futures from a stream concurrently (unordered).

This stream’s Ok type must be a TryFuture with an Error type that matches the stream’s Error type.

This adaptor will buffer up to n futures and then return their outputs in the order in which they complete. If the underlying stream returns an error, it will be immediately propagated.

The limit argument is of type Into<Option<usize>>, and so can be provided as either None, Some(10), or just 10. Note: a limit of zero is interpreted as no limit at all, and will have the same result as passing in None.

The returned stream will be a stream of results, each containing either an error or a future’s output. An error can be produced either by the underlying stream itself or by one of the futures it yielded.

This method is only available when the std or alloc feature of this library is activated, and it is activated by default.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

  #[tokio::main]
  async fn main() {
    let unordered = tokio_stream::iter(vec![Ok::<i32, &str>(3), Ok(1), Ok(2)])
        .map_ok(async |i| if i == 2 { Err("error") } else { Ok(i) })
        .try_buffer_unordered(None);

    let mut out = unordered.into_stream().collect::<Vec<_>>().await;
    out.sort();
    assert_eq!(out, vec![Ok(1), Ok(3), Err("error")]);
}

fn try_buffered(self, n: impl Into<Option<usize>>) -> TryBuffered<Self>

where Self::Ok: TryFuture<Error = Self::Error>, Self: Sized,

Attempt to execute several futures from a stream concurrently.

This stream’s Ok type must be a TryFuture with an Error type that matches the stream’s Error type.

This adaptor will buffer up to n futures and then return their outputs in the same order as the underlying stream. If the underlying stream returns an error, it will be immediately propagated.

The limit argument is of type Into<Option<usize>>, and so can be provided as either None, Some(10), or just 10. Note: a limit of zero is interpreted as no limit at all, and will have the same result as passing in None.

The returned stream will be a stream of results, each containing either an error or a future’s output. An error can be produced either by the underlying stream itself or by one of the futures it yielded.

This method is only available when the std or alloc feature of this library is activated, and it is activated by default.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

#[tokio::main]
async fn main() {
    let buffered = tokio_stream::iter(vec![Ok::<i32, &str>(3), Ok(1), Ok(2)])
        .map_ok(|i| async move { if i == 2 { Err("error") } else { Ok(i) } })
        .try_buffered(None);

    let out = buffered.into_stream().collect::<Vec<_>>().await;
    assert_eq!(out, vec![Ok(3), Ok(1), Err("error")]);
}

fn try_poll_next_unpin( &mut self, cx: &mut Context<'_>, ) -> Poll<Option<Result<Self::Ok, Self::Error>>>

where Self: Unpin,

A convenience method for calling TryStream::try_poll_next on Unpin stream types.

fn try_all<Fut, F>(self, f: F) -> TryAll<Self, Fut, F>

where Self: Sized, F: FnMut(Self::Ok) -> Fut, Fut: Future<Output = bool>,

Attempt to execute a predicate over an asynchronous stream and evaluate if all items satisfy the predicate. Exits early if an Err is encountered or if an Ok item is found that does not satisfy the predicate.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let future_true = tokio_stream::iter(vec![1, 2, 3]).map(|i| Ok::<i32, &str>(i))
        .try_all(|i| async move { i > 0 });
    assert!(future_true.await.unwrap());

    let future_err = tokio_stream::iter(vec![Ok::<i32, &str>(1), Err("err"), Ok(3)])
        .try_all(|i| async move { i > 0 });
    assert!(future_err.await.is_err());
});

fn try_any<Fut, F>(self, f: F) -> TryAny<Self, Fut, F>

where Self: Sized, F: FnMut(Self::Ok) -> Fut, Fut: Future<Output = bool>,

Attempt to execute a predicate over an asynchronous stream and evaluate if any items satisfy the predicate. Exits early if an Err is encountered or if an Ok item is found that satisfies the predicate.

Examples

use tokio_stream::StreamExt;
use tokio_stream_util::TryStreamExt;

let rt = tokio::runtime::Builder::new_current_thread().enable_all().build().unwrap();
rt.block_on(async {
    let future_true = tokio_stream::iter(0..10).map(|i| Ok::<i32, &str>(i))
        .try_any(|i| async move { i == 3 });
    assert!(future_true.await.unwrap());

    let future_err = tokio_stream::iter(vec![Ok::<i32, &str>(1), Err("err"), Ok(3)])
        .try_any(|i| async move { i == 3 });
    assert!(future_err.await.is_err());
});

Dyn Compatibility

This trait is not dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety", so this trait is not object safe.

Implementors

impl<S: ?Sized + TryStream> TryStreamExt for S