Class ReduceOperator

Namespace

RxSharp.Operators

Assembly

RxSharp.dll

Extension methods implementing the reduce operator.

public static class ReduceOperator

Inheritance

System.Object

ReduceOperator

Remarks

Behaves like ScanOperator, except only the final accumulated value is emitted, once source completes, rather than the running value after every emission. Implemented standalone (not as Scan(...).Last()) since this port has no Last operator yet.

Methods

Reduce<T>(Observable<T>, Func<T, T, int, T>)

Applies accumulator to each value emitted by source, along with its zero-based index, emitting only the final accumulated value once source completes. There is no seed: the first value emitted by source becomes the initial accumulated state, without ever being passed to accumulator.

public static Observable<T> Reduce<T>(this Observable<T> source, Func<T, T, int, T> accumulator)

Parameters

source Observable<T>

The source sequence.

accumulator Func<T, T, int, T>

A function called with the current accumulated state, the source value, and its index (starting at 1, since index 0 is consumed as the seed); returns the new accumulated state.

Returns

Observable<T>

An observable that emits the final accumulated value once source completes, if it ever emitted.

Type Parameters

T

The type of values emitted by source and of the output.

Remarks

If source completes without ever emitting, the output completes without emitting any value either (there being no first value to seed with). Because the first value is used directly as the seed, accumulator is first called (with index 1) on the second source value, not the first. If accumulator throws, the exception is forwarded via OnError.

Reduce<T>(Observable<T>, Func<T, T, T>)

Applies accumulator to each value emitted by source, emitting only the final accumulated value once source completes. There is no seed: the first value emitted by source becomes the initial accumulated state, without ever being passed to accumulator.

public static Observable<T> Reduce<T>(this Observable<T> source, Func<T, T, T> accumulator)

Parameters

source Observable<T>

The source sequence.

accumulator Func<T, T, T>

A function called with the current accumulated state and the source value; returns the new accumulated state.

Returns

Observable<T>

An observable that emits the final accumulated value once source completes, if it ever emitted.

Type Parameters

T

The type of values emitted by source and of the output.

Remarks

Equivalent to the indexed overload with the index ignored. See its remarks for full behavior.

Reduce<TSource, TAcc>(Observable<TSource>, Func<TAcc, TSource, int, TAcc>, TAcc)

Applies accumulator to seed and each value emitted by source, along with its zero-based index, emitting only the final accumulated value once source completes.

public static Observable<TAcc> Reduce<TSource, TAcc>(this Observable<TSource> source, Func<TAcc, TSource, int, TAcc> accumulator, TAcc seed)

Parameters

source Observable<TSource>

The source sequence.

accumulator Func<TAcc, TSource, int, TAcc>

A function called with the current accumulated state, the source value, and its index (starting at 0); returns the new accumulated state.

seed TAcc

The initial accumulated state.

Returns

Observable<TAcc>

An observable that emits the final accumulated value once source completes.

Type Parameters

TSource

The type of values emitted by source.

TAcc

The type of the accumulated state and of the output value.

Remarks

If source completes without ever emitting, the final value is seed itself. If accumulator throws, the exception is forwarded to the subscriber via OnError instead of propagating synchronously, and no value is ever emitted.

Reduce<TSource, TAcc>(Observable<TSource>, Func<TAcc, TSource, TAcc>, TAcc)

Applies accumulator to seed and each value emitted by source, emitting only the final accumulated value once source completes.

public static Observable<TAcc> Reduce<TSource, TAcc>(this Observable<TSource> source, Func<TAcc, TSource, TAcc> accumulator, TAcc seed)

Parameters

source Observable<TSource>

The source sequence.

accumulator Func<TAcc, TSource, TAcc>

A function called with the current accumulated state and the source value; returns the new accumulated state.

seed TAcc

The initial accumulated state.

Returns

Observable<TAcc>

An observable that emits the final accumulated value once source completes.

Type Parameters

TSource

The type of values emitted by source.

TAcc

The type of the accumulated state and of the output value.

Remarks

Equivalent to the indexed overload with the index ignored. See its remarks for full behavior.