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47 lines
2.3 KiB
47 lines
2.3 KiB
import { Observable } from '../Observable'; |
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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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* @example <caption>A simple example with numbers</caption> |
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* Observable.of(1, 1, 2, 2, 2, 1, 2, 3, 4, 3, 2, 1) |
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* .distinct() |
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* .subscribe(x => console.log(x)); // 1, 2, 3, 4 |
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* |
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* @example <caption>An example using a keySelector function</caption> |
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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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* Observable.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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* .distinct((p: Person) => p.name) |
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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>(this: Observable<T>, keySelector?: (value: T) => K, flushes?: Observable<any>): Observable<T>;
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