79 lines
3 KiB
TypeScript
79 lines
3 KiB
TypeScript
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import { Observable } from '../Observable';
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import { Subscriber } from '../Subscriber';
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import { MonoTypeOperatorFunction } from '../types';
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import { SimpleOuterSubscriber } from '../innerSubscribe';
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/**
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* Returns an Observable that emits all items emitted by the source Observable that are distinct by comparison from previous items.
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*
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* If a keySelector function is provided, then it will project each value from the source observable into a new value that it will
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* check for equality with previously projected values. If a keySelector function is not provided, it will use each value from the
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* source observable directly with an equality check against previous values.
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*
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* In JavaScript runtimes that support `Set`, this operator will use a `Set` to improve performance of the distinct value checking.
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*
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* In other runtimes, this operator will use a minimal implementation of `Set` that relies on an `Array` and `indexOf` under the
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* hood, so performance will degrade as more values are checked for distinction. Even in newer browsers, a long-running `distinct`
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* use might result in memory leaks. To help alleviate this in some scenarios, an optional `flushes` parameter is also provided so
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* that the internal `Set` can be "flushed", basically clearing it of values.
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*
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* ## Examples
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* A simple example with numbers
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* ```ts
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* import { of } from 'rxjs';
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* import { distinct } from 'rxjs/operators';
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*
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* of(1, 1, 2, 2, 2, 1, 2, 3, 4, 3, 2, 1).pipe(
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* distinct(),
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* )
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* .subscribe(x => console.log(x)); // 1, 2, 3, 4
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* ```
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*
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* An example using a keySelector function
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* ```typescript
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* import { of } from 'rxjs';
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* import { distinct } from 'rxjs/operators';
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*
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* interface Person {
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* age: number,
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* name: string
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* }
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*
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* of<Person>(
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* { age: 4, name: 'Foo'},
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* { age: 7, name: 'Bar'},
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* { age: 5, name: 'Foo'},
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* ).pipe(
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* distinct((p: Person) => p.name),
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* )
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* .subscribe(x => console.log(x));
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*
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* // displays:
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* // { age: 4, name: 'Foo' }
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* // { age: 7, name: 'Bar' }
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* ```
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* @see {@link distinctUntilChanged}
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* @see {@link distinctUntilKeyChanged}
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*
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* @param {function} [keySelector] Optional function to select which value you want to check as distinct.
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* @param {Observable} [flushes] Optional Observable for flushing the internal HashSet of the operator.
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* @return {Observable} An Observable that emits items from the source Observable with distinct values.
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* @method distinct
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* @owner Observable
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*/
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export declare function distinct<T, K>(keySelector?: (value: T) => K, flushes?: Observable<any>): MonoTypeOperatorFunction<T>;
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/**
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* We need this JSDoc comment for affecting ESDoc.
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* @ignore
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* @extends {Ignored}
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*/
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export declare class DistinctSubscriber<T, K> extends SimpleOuterSubscriber<T, T> {
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private keySelector?;
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private values;
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constructor(destination: Subscriber<T>, keySelector?: (value: T) => K, flushes?: Observable<any>);
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notifyNext(): void;
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notifyError(error: any): void;
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protected _next(value: T): void;
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private _useKeySelector;
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private _finalizeNext;
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}
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