DataReaderAsyncExtensions Class Reference

Provides extensions to DataReader<T> More...

Static Public Member Functions
static IAsyncEnumerable< LoanedSample< T > >	TakeAsync< T > (this DataReader< T > reader)
	Provides an infinite asynchronous enumerable that returns new samples from a reader as they become available. More...
static IAsyncEnumerable< LoanedSample< T > >	TakeAsync< T > (this Selector< T > selector)
	Provides an infinite asynchronous enumerable that returns new samples from a reader selector as they become available. More...
static async IAsyncEnumerable< T >	ValidData< T > (this IAsyncEnumerable< LoanedSample< T >> samples, [EnumeratorCancellation] CancellationToken cancellationToken=default)
	Filters a sequence of samples, returning valid data only. More...

Detailed Description

Provides extensions to DataReader<T>

Note

These extensions are included in the Rti.ConnextDds.Extra package.

Member Function Documentation

TakeAsync< T >() [1/2]

static IAsyncEnumerable<LoanedSample<T> > TakeAsync< T > ( this DataReader< T >  reader )

static

Provides an infinite asynchronous enumerable that returns new samples from a reader as they become available.

Parameters

reader

The reader where the samples come from

Template Parameters

T	The reader's topic-type

When an element of the returned IAsyncEnumerable is requested, if the reader has any data available, it returns it immediately. Otherwise it awaits until new data is available.

The simplest way to use this function is an infinite loop that prints the data as the reader receives it:

await foreach (var sample in reader.TakeAsync())
{
    if (sample.Info.ValidData)
    {
        Console.WriteLine($"Received data: {sample.Data}");
    }
}

Warning

Each element (LoanedSample<T>) is only valid until the enumerable advances to the next element. The sample or any reference to the sample's fields can no longer be accessed after the enumerable moves to the next sample.

The enumerable can receive a cancellation token, for example:

var cancel = new CancellationTokenSource();
 
// A:
await foreach (var sample in reader.TakeAsync().WithCancellation(cancel.Token))
{
    ...
}
 
// B:
cancel.Cancel();

Warning

The disposal of the DataReader or the Subscriber and DomainParticipant that contains it may fail while the iterator is active. Use a cancellation token to ensure TakeAsync() finishes before disposing said entities.

See also

Reading data asynchronously for more code examples.

TakeAsync< T >() [2/2]

static IAsyncEnumerable<LoanedSample<T> > TakeAsync< T > ( this Selector< T >  selector )

static

Provides an infinite asynchronous enumerable that returns new samples from a reader selector as they become available.

Parameters

selector

A selector created with DataReader<T>.Select

Template Parameters

T	The reader's topic-type

See also

TakeAsync<T>(DataReader<T>)

ValidData< T >()

static async IAsyncEnumerable<T> ValidData< T > ( this IAsyncEnumerable< LoanedSample< T >>  samples, [EnumeratorCancellation] CancellationToken  cancellationToken = default  )

static

Filters a sequence of samples, returning valid data only.

Parameters

samples	A IAsyncEnumerable of loaned samples: the result of TakeAsync()
cancellationToken	A cancellation token, automatically set by the compiler when .WithCancellation() is used.

Returns

A new IAsyncEnumerable such that, for each LoanedSample<T> s in samples, it returns s.Data only if s.Info.ValidData is true.

Just like TakeAsync, only the current T object in the iteration is valid at a given moment; as soon as the iterator advances, that object becomes invalid and can no longer be accessed (unless its copied)