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