distinct.d.ts 3.1 KB

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  1. import { Observable } from '../Observable';
  2. import { Subscriber } from '../Subscriber';
  3. import { OuterSubscriber } from '../OuterSubscriber';
  4. import { InnerSubscriber } from '../InnerSubscriber';
  5. import { MonoTypeOperatorFunction } from '../interfaces';
  6. /**
  7. * Returns an Observable that emits all items emitted by the source Observable that are distinct by comparison from previous items.
  8. *
  9. * If a keySelector function is provided, then it will project each value from the source observable into a new value that it will
  10. * check for equality with previously projected values. If a keySelector function is not provided, it will use each value from the
  11. * source observable directly with an equality check against previous values.
  12. *
  13. * In JavaScript runtimes that support `Set`, this operator will use a `Set` to improve performance of the distinct value checking.
  14. *
  15. * In other runtimes, this operator will use a minimal implementation of `Set` that relies on an `Array` and `indexOf` under the
  16. * hood, so performance will degrade as more values are checked for distinction. Even in newer browsers, a long-running `distinct`
  17. * use might result in memory leaks. To help alleviate this in some scenarios, an optional `flushes` parameter is also provided so
  18. * that the internal `Set` can be "flushed", basically clearing it of values.
  19. *
  20. * @example <caption>A simple example with numbers</caption>
  21. * Observable.of(1, 1, 2, 2, 2, 1, 2, 3, 4, 3, 2, 1)
  22. * .distinct()
  23. * .subscribe(x => console.log(x)); // 1, 2, 3, 4
  24. *
  25. * @example <caption>An example using a keySelector function</caption>
  26. * interface Person {
  27. * age: number,
  28. * name: string
  29. * }
  30. *
  31. * Observable.of<Person>(
  32. * { age: 4, name: 'Foo'},
  33. * { age: 7, name: 'Bar'},
  34. * { age: 5, name: 'Foo'})
  35. * .distinct((p: Person) => p.name)
  36. * .subscribe(x => console.log(x));
  37. *
  38. * // displays:
  39. * // { age: 4, name: 'Foo' }
  40. * // { age: 7, name: 'Bar' }
  41. *
  42. * @see {@link distinctUntilChanged}
  43. * @see {@link distinctUntilKeyChanged}
  44. *
  45. * @param {function} [keySelector] Optional function to select which value you want to check as distinct.
  46. * @param {Observable} [flushes] Optional Observable for flushing the internal HashSet of the operator.
  47. * @return {Observable} An Observable that emits items from the source Observable with distinct values.
  48. * @method distinct
  49. * @owner Observable
  50. */
  51. export declare function distinct<T, K>(keySelector?: (value: T) => K, flushes?: Observable<any>): MonoTypeOperatorFunction<T>;
  52. /**
  53. * We need this JSDoc comment for affecting ESDoc.
  54. * @ignore
  55. * @extends {Ignored}
  56. */
  57. export declare class DistinctSubscriber<T, K> extends OuterSubscriber<T, T> {
  58. private keySelector;
  59. private values;
  60. constructor(destination: Subscriber<T>, keySelector: (value: T) => K, flushes: Observable<any>);
  61. notifyNext(outerValue: T, innerValue: T, outerIndex: number, innerIndex: number, innerSub: InnerSubscriber<T, T>): void;
  62. notifyError(error: any, innerSub: InnerSubscriber<T, T>): void;
  63. protected _next(value: T): void;
  64. private _useKeySelector(value);
  65. private _finalizeNext(key, value);
  66. }