pub enum Either<A, B> {
    Left(A),
    Right(B),
}
Expand description

Combines two different futures, streams, or sinks having the same associated types into a single type.

This is useful when conditionally choosing between two distinct future types:

use futures::future::Either;

let cond = true;

let fut = if cond {
    Either::Left(async move { 12 })
} else {
    Either::Right(async move { 44 })
};

assert_eq!(fut.await, 12);

Variants§

§

Left(A)

First branch of the type

§

Right(B)

Second branch of the type

Implementations§

Convert Pin<&Either<A, B>> to Either<Pin<&A>, Pin<&B>>, pinned projections of the inner variants.

Convert Pin<&mut Either<A, B>> to Either<Pin<&mut A>, Pin<&mut B>>, pinned projections of the inner variants.

Factor out a homogeneous type from an either of pairs.

Here, the homogeneous type is the first element of the pairs.

Factor out a homogeneous type from an either of pairs.

Here, the homogeneous type is the second element of the pairs.

Extract the value of an either over two equivalent types.

Trait Implementations§

Attempt to return the contents of the internal buffer, filling it with more data from the inner reader if it is empty. Read more
Tells this buffer that amt bytes have been consumed from the buffer, so they should no longer be returned in calls to poll_read. Read more
Attempt to read from the AsyncRead into buf. Read more
Attempt to read from the AsyncRead into bufs using vectored IO operations. Read more
Attempt to seek to an offset, in bytes, in a stream. Read more
Attempt to write bytes from buf into the object. Read more
Attempt to write bytes from bufs into the object using vectored IO operations. Read more
Attempt to flush the object, ensuring that any buffered data reach their destination. Read more
Attempt to close the object. Read more
Returns a copy of the value. Read more
Performs copy-assignment from source. Read more
Formats the value using the given formatter. Read more
Returns true if the underlying future should no longer be polled.
Returns true if the stream should no longer be polled.
The type of value produced on completion.
Attempt to resolve the future to a final value, registering the current task for wakeup if the value is not yet available. Read more
The type of value produced by the sink when an error occurs.
Attempts to prepare the Sink to receive a value. Read more
Begin the process of sending a value to the sink. Each call to this function must be preceded by a successful call to poll_ready which returned Poll::Ready(Ok(())). Read more
Flush any remaining output from this sink. Read more
Flush any remaining output and close this sink, if necessary. Read more
Values yielded by the stream.
Attempt to pull out the next value of this stream, registering the current task for wakeup if the value is not yet available, and returning None if the stream is exhausted. Read more
Returns the bounds on the remaining length of the stream. Read more

Auto Trait Implementations§

Blanket Implementations§

Gets the TypeId of self. Read more
Creates a future which will wait for a non-empty buffer to be available from this I/O object or EOF to be reached. Read more
A convenience for calling AsyncBufRead::consume on Unpin IO types. Read more
Creates a future which will read all the bytes associated with this I/O object into buf until the delimiter byte or EOF is reached. This method is the async equivalent to BufRead::read_until. Read more
Creates a future which will read all the bytes associated with this I/O object into buf until a newline (the 0xA byte) or EOF is reached, This method is the async equivalent to BufRead::read_line. Read more
Returns a stream over the lines of this reader. This method is the async equivalent to BufRead::lines. Read more
Creates an adaptor which will chain this stream with another. Read more
Tries to read some bytes directly into the given buf in asynchronous manner, returning a future type. Read more
Creates a future which will read from the AsyncRead into bufs using vectored IO operations. Read more
Creates a future which will read exactly enough bytes to fill buf, returning an error if end of file (EOF) is hit sooner. Read more
Creates a future which will read all the bytes from this AsyncRead. Read more
Creates a future which will read all the bytes from this AsyncRead. Read more
Helper method for splitting this read/write object into two halves. Read more
Creates an AsyncRead adapter which will read at most limit bytes from the underlying reader. Read more
Creates a future which will seek an IO object, and then yield the new position in the object and the object itself. Read more
Creates a future which will return the current seek position from the start of the stream. Read more
Creates a future which will entirely flush this AsyncWrite. Read more
Creates a future which will entirely close this AsyncWrite.
Creates a future which will write bytes from buf into the object. Read more
Creates a future which will write bytes from bufs into the object using vectored IO operations. Read more
Write data into this object. Read more
Allow using an AsyncWrite as a Sink<Item: AsRef<[u8]>>. Read more
Immutably borrows from an owned value. Read more
Mutably borrows from an owned value. Read more

Returns the argument unchanged.

Map this future’s output to a different type, returning a new future of the resulting type. Read more
Map this future’s output to a different type, returning a new future of the resulting type. Read more
Chain on a computation for when a future finished, passing the result of the future to the provided closure f. Read more
Wrap this future in an Either future, making it the left-hand variant of that Either. Read more
Wrap this future in an Either future, making it the right-hand variant of that Either. Read more
Convert this future into a single element stream. Read more
Flatten the execution of this future when the output of this future is itself another future. Read more
Flatten the execution of this future when the successful result of this future is a stream. Read more
Fuse a future such that poll will never again be called once it has completed. This method can be used to turn any Future into a FusedFuture. Read more
Do something with the output of a future before passing it on. Read more
Catches unwinding panics while polling the future. Read more
Create a cloneable handle to this future where all handles will resolve to the same result. Read more
Turn this future into a future that yields () on completion and sends its output to another future on a separate task. Read more
Wrap the future in a Box, pinning it. Read more
Wrap the future in a Box, pinning it. Read more
A convenience for calling Future::poll on Unpin future types.
Evaluates and consumes the future, returning the resulting output if the future is ready after the first call to Future::poll. Read more

Calls U::from(self).

That is, this conversion is whatever the implementation of From<T> for U chooses to do.

The output that the future will produce on completion.
Which kind of future are we turning this into?
Creates a future from a value. Read more
Composes a function in front of the sink. Read more
Composes a function in front of the sink. Read more
Transforms the error returned by the sink.
Map this sink’s error to a different error type using the Into trait. Read more
Adds a fixed-size buffer to the current sink. Read more
Close the sink.
Fanout items to multiple sinks. Read more
Flush the sink, processing all pending items. Read more
A future that completes after the given item has been fully processed into the sink, including flushing. Read more
A future that completes after the given item has been received by the sink. Read more
A future that completes after the given stream has been fully processed into the sink, including flushing. Read more
Wrap this sink in an Either sink, making it the left-hand variant of that Either. Read more
Wrap this stream in an Either stream, making it the right-hand variant of that Either. Read more
A convenience method for calling Sink::poll_ready on Unpin sink types.
A convenience method for calling Sink::start_send on Unpin sink types.
A convenience method for calling Sink::poll_flush on Unpin sink types.
A convenience method for calling Sink::poll_close on Unpin sink types.
Creates a future that resolves to the next item in the stream. Read more
Converts this stream into a future of (next_item, tail_of_stream). If the stream terminates, then the next item is None. Read more
Maps this stream’s items to a different type, returning a new stream of the resulting type. Read more
Creates a stream which gives the current iteration count as well as the next value. Read more
Filters the values produced by this stream according to the provided asynchronous predicate. Read more
Filters the values produced by this stream while simultaneously mapping them to a different type according to the provided asynchronous closure. Read more
Computes from this stream’s items new items of a different type using an asynchronous closure. Read more
Transforms a stream into a collection, returning a future representing the result of that computation. Read more
Converts a stream of pairs into a future, which resolves to pair of containers. Read more
Concatenate all items of a stream into a single extendable destination, returning a future representing the end result. Read more
Drives the stream to completion, counting the number of items. Read more
Repeats a stream endlessly. Read more
Execute an accumulating asynchronous computation over a stream, collecting all the values into one final result. Read more
Execute predicate over asynchronous stream, and return true if any element in stream satisfied a predicate. Read more
Execute predicate over asynchronous stream, and return true if all element in stream satisfied a predicate. Read more
Flattens a stream of streams into just one continuous stream. Read more
Flattens a stream of streams into just one continuous stream. Polls inner streams produced by the base stream concurrently. Read more
Maps a stream like StreamExt::map but flattens nested Streams. Read more
Maps a stream like StreamExt::map but flattens nested Streams and polls them concurrently, yielding items in any order, as they made available. Read more
Combinator similar to StreamExt::fold that holds internal state and produces a new stream. Read more
Skip elements on this stream while the provided asynchronous predicate resolves to true. Read more
Take elements from this stream while the provided asynchronous predicate resolves to true. Read more
Take elements from this stream until the provided future resolves. Read more
Runs this stream to completion, executing the provided asynchronous closure for each element on the stream. Read more
Runs this stream to completion, executing the provided asynchronous closure for each element on the stream concurrently as elements become available. Read more
Creates a new stream of at most n items of the underlying stream. Read more
Creates a new stream which skips n items of the underlying stream. Read more
Fuse a stream such that poll_next will never again be called once it has finished. This method can be used to turn any Stream into a FusedStream. Read more
Borrows a stream, rather than consuming it. Read more
Catches unwinding panics while polling the stream. Read more
Wrap the stream in a Box, pinning it. Read more
Wrap the stream in a Box, pinning it. Read more
An adaptor for creating a buffered list of pending futures. Read more
An adaptor for creating a buffered list of pending futures (unordered). Read more
An adapter for zipping two streams together. Read more
Adapter for chaining two streams. Read more
Creates a new stream which exposes a peek method. Read more
An adaptor for chunking up items of the stream inside a vector. Read more
An adaptor for chunking up ready items of the stream inside a vector. Read more
A future that completes after the given stream has been fully processed into the sink and the sink has been flushed and closed. Read more
Splits this Stream + Sink object into separate Sink and Stream objects. Read more
Do something with each item of this stream, afterwards passing it on. Read more
Wrap this stream in an Either stream, making it the left-hand variant of that Either. Read more
Wrap this stream in an Either stream, making it the right-hand variant of that Either. Read more
A convenience method for calling Stream::poll_next on Unpin stream types.
Returns a Future that resolves when the next item in this stream is ready. Read more
The resulting type after obtaining ownership.
Creates owned data from borrowed data, usually by cloning. Read more
Uses borrowed data to replace owned data, usually by cloning. Read more
The type returned in the event of a conversion error.
Performs the conversion.
The type of successful values yielded by this future
The type of failures yielded by this future
Poll this TryFuture as if it were a Future. Read more
Flattens the execution of this future when the successful result of this future is a Sink. Read more
Maps this future’s success value to a different value. Read more
Maps this future’s success value to a different value, and permits for error handling resulting in the same type. Read more
Maps this future’s error value to a different value. Read more
Maps this future’s Error to a new error type using the Into trait. Read more
Maps this future’s Ok to a new type using the Into trait.
Executes another future after this one resolves successfully. The success value is passed to a closure to create this subsequent future. Read more
Executes another future if this one resolves to an error. The error value is passed to a closure to create this subsequent future. Read more
Do something with the success value of a future before passing it on. Read more
Do something with the error value of a future before passing it on. Read more
Flatten the execution of this future when the successful result of this future is another future. Read more
Flatten the execution of this future when the successful result of this future is a stream. Read more
Unwraps this future’s output, producing a future with this future’s Ok type as its Output type. Read more
Wraps a TryFuture into a type that implements Future. Read more
A convenience method for calling TryFuture::try_poll on Unpin future types.
The type returned in the event of a conversion error.
Performs the conversion.
The type of successful values yielded by this future
The type of failures yielded by this future
Poll this TryStream as if it were a Stream. Read more
Wraps the current stream in a new stream which converts the error type into the one provided. Read more
Wraps the current stream in a new stream which maps the success value using the provided closure. Read more
Wraps the current stream in a new stream which maps the error value using the provided closure. Read more
Chain on a computation for when a value is ready, passing the successful results to the provided closure f. Read more
Chain on a computation for when an error happens, passing the erroneous result to the provided closure f. Read more
Do something with the success value of this stream, afterwards passing it on. Read more
Do something with the error value of this stream, afterwards passing it on. Read more
Wraps a TryStream into a type that implements Stream Read more
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. Read more
Attempts to run this stream to completion, executing the provided asynchronous closure for each element on the stream. Read more
Skip elements on this stream while the provided asynchronous predicate resolves to true. Read more
Take elements on this stream while the provided asynchronous predicate resolves to true. Read more
Attempts to run this stream to completion, executing the provided asynchronous closure for each element on the stream concurrently as elements become available, exiting as soon as an error occurs. Read more
Attempt to transform a stream into a collection, returning a future representing the result of that computation. Read more
An adaptor for chunking up successful items of the stream inside a vector. Read more
Attempt to filter the values produced by this stream according to the provided asynchronous closure. Read more
Attempt to filter the values produced by this stream while simultaneously mapping them to a different type according to the provided asynchronous closure. Read more
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. Read more
Flattens a stream of streams into just one continuous stream. Read more
Attempt to execute an accumulating asynchronous computation over a stream, collecting all the values into one final result. Read more
Attempt to concatenate all items of a stream into a single extendable destination, returning a future representing the end result. Read more
Attempt to execute several futures from a stream concurrently (unordered). Read more
Attempt to execute several futures from a stream concurrently. Read more
A convenience method for calling TryStream::try_poll_next on Unpin stream types.
Adapter that converts this stream into an AsyncBufRead. Read more