Class ScanOperator

Namespace

RxSharp.Operators

Assembly

RxSharp.dll

Extension methods implementing the scan operator.

public static class ScanOperator

Inheritance

System.Object

ScanOperator

Remarks

Unlike MergeScanOperator, scan's accumulator returns a plain value synchronously instead of an inner observable, so every accumulation happens inline with no concurrency to manage.

Methods

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

Applies accumulator to each value emitted by source, along with its zero-based index, emitting the updated accumulator value after every source emission after the first. There is no seed: the first value emitted by source becomes the initial accumulated state and is emitted as-is, without ever being passed to accumulator.

public static Observable<T> Scan<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 of the running accumulator value after each source emission but the first.

Type Parameters

T

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

Remarks

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 to the subscriber via OnError instead of propagating synchronously. If source completes without ever emitting, the output simply completes without ever emitting either (there being no first value to seed with).

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

Applies accumulator to each value emitted by source, emitting the updated accumulator value after every source emission after the first. There is no seed: the first value emitted by source becomes the initial accumulated state and is emitted as-is, without ever being passed to accumulator.

public static Observable<T> Scan<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 of the running accumulator value after each source emission but the first.

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.

Scan<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 the updated accumulator value after every source emission.

public static Observable<TAcc> Scan<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 of the running accumulator value after each source emission.

Type Parameters

TSource

The type of values emitted by source.

TAcc

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

Remarks

If accumulator throws, the exception is forwarded to the subscriber via OnError instead of propagating synchronously.

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

Applies accumulator to seed and each value emitted by source, emitting the updated accumulator value after every source emission.

public static Observable<TAcc> Scan<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 of the running accumulator value after each source emission.

Type Parameters

TSource

The type of values emitted by source.

TAcc

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

Remarks

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