Class DistinctUntilChangedOperator

Namespace

RxSharp.Operators

Assembly

RxSharp.dll

Implements the DistinctUntilChanged operator. Mirrors rxjs's distinctUntilChanged.

public static class DistinctUntilChangedOperator

Inheritance

System.Object

DistinctUntilChangedOperator

Methods

DistinctUntilChanged<T>(Observable<T>, IEqualityComparer<T>?)

Emits a value from source only when it differs from the immediately preceding emitted value, using comparer (or the default equality comparer for T).

public static Observable<T> DistinctUntilChanged<T>(this Observable<T> source, IEqualityComparer<T>? comparer = null)

Parameters

source Observable<T>

The source observable to filter for consecutive distinct values.

comparer IEqualityComparer<T>?

The comparer used to test equality. Defaults to EqualityComparer<T>.Default when null.

Returns

Observable<T>

An observable that suppresses consecutive duplicate values from source.

Type Parameters

T

The element type of the source observable.

Remarks

The first value is always emitted. Comparison is only ever against the last value that was actually emitted downstream, not against every previously seen value — so a value can reappear later in the stream if something different was emitted in between (e.g. 1, 1, 2, 1 emits 1, 2, 1).

DistinctUntilChanged<T, TKey>(Observable<T>, IEqualityComparer<TKey>, Func<T, TKey>)

Emits a value from source only when the key computed for it by keySelector differs, per comparer, from the key computed for the immediately preceding emitted value.

public static Observable<T> DistinctUntilChanged<T, TKey>(this Observable<T> source, IEqualityComparer<TKey> comparer, Func<T, TKey> keySelector)

Parameters

source Observable<T>

The source observable to filter for consecutive distinct keys.

comparer IEqualityComparer<TKey>

The comparer used to test key equality.

keySelector Func<T, TKey>

A function that extracts the comparison key from each value.

Returns

Observable<T>

An observable that suppresses values whose key matches the previously emitted value's key.

Type Parameters

T

The element type of the source observable.

TKey

The type of the key extracted from each value for comparison purposes.

Remarks

The first value is always emitted (after having its key computed). keySelector runs on every value, including the first. Only the computed key is compared and retained between emissions; the original value (not the key) is what gets emitted. If keySelector throws, the exception is forwarded via OnError and the source subscription is torn down.

DistinctUntilKeyChanged<T, TKey>(Observable<T>, Func<T, TKey>, IEqualityComparer<TKey>?)

Emits a value from source only when the key computed for it by keySelector differs, per comparer, from the key computed for the immediately preceding emitted value.

public static Observable<T> DistinctUntilKeyChanged<T, TKey>(this Observable<T> source, Func<T, TKey> keySelector, IEqualityComparer<TKey>? comparer = null)

Parameters

source Observable<T>

The source observable to filter for consecutive distinct keys.

keySelector Func<T, TKey>

A function that extracts the comparison key from each value.

comparer IEqualityComparer<TKey>?

The comparer used to test key equality. Defaults to EqualityComparer<TKey>.Default when null.

Returns

Observable<T>

An observable that suppresses values whose key matches the previously emitted value's key.

Type Parameters

T

The element type of the source observable.

TKey

The type of the key extracted from each value for comparison purposes.

Remarks

A thin, more strongly-typed wrapper over DistinctUntilChanged<T, TKey>(Observable<T>, IEqualityComparer<TKey>, Func<T, TKey>) — rxjs's distinctUntilKeyChanged takes a string property-name key (JS objects are dynamically typed); this takes a keySelector function instead, the natural C# equivalent. The first value is always emitted. If keySelector throws, the exception is forwarded via OnError.