Class OfTypeTransformer<TSource, TDestination>

Namespace: Wolfgang.Etl.Transformers

Assembly: Wolfgang.Etl.Transformers.dll

A transformer that yields each input item that is of type TDestination, silently skipping items of any other type.

public sealed class OfTypeTransformer<TSource, TDestination> : ITransformAsync<TSource, TDestination> where TSource : notnull where TDestination : notnull

Type Parameters

TSource: The type of items in the input sequence. Must be non-null.
TDestination: The type to filter for. Must be non-null. No compile-time relationship with TSource is required - the check is a runtime is test.

Inheritance: object

OfTypeTransformer<TSource, TDestination>

Implements: ITransformAsync<TSource, TDestination>

Inherited Members: object.Equals(object)

object.Equals(object, object)

object.GetHashCode()

object.GetType()

object.ReferenceEquals(object, object)

object.ToString()

Extension Methods: TransformerExtensions.Then<TSource, TIntermediate, TDestination>(ITransformAsync<TSource, TIntermediate>, ITransformAsync<TIntermediate, TDestination>)

Examples

// pull the strings out of a heterogeneous object stream
var strings = new OfTypeTransformer<object, string>();

// narrow an animal stream to only the dogs
var dogs = new OfTypeTransformer<Animal, Dog>();

Remarks

OfTypeTransformer<TSource, TDestination> is the transformer equivalent of LINQ's OfType<TResult>(IEnumerable): it filters and casts in a single step, yielding only items that satisfy item is TDestination.

Items that do not match TDestination are silently skipped - this transformer never throws InvalidCastException. Use CastTransformer<TSource, TDestination> instead if mismatched items should raise an exception rather than be filtered out.

null items (which can technically appear if the source bypasses the notnull constraint via null!) are also skipped, since null is T is false for any T.

Implements only Wolfgang.Etl.Abstractions.ITransformAsync<TSource, TDestination> - no progress, no cancellation, no Skip/Max - to keep the hot loop minimal.

Constructors

OfTypeTransformer()

Initializes a new instance of the OfTypeTransformer<TSource, TDestination> class.

public OfTypeTransformer()

Methods

TransformAsync(IAsyncEnumerable<TSource>)

Asynchronously yields each item from items that is an instance of TDestination.

public IAsyncEnumerable<TDestination> TransformAsync(IAsyncEnumerable<TSource> items)

Parameters

items IAsyncEnumerable<TSource>: The asynchronous source sequence.

Returns

IAsyncEnumerable<TDestination>: An asynchronous sequence containing only those input items that are of type TDestination, cast to that type.

Exceptions

ArgumentNullException: items is null.