| import { Operator } from '../Operator'; |
| import { Subscriber } from '../Subscriber'; |
| import { Observable } from '../Observable'; |
| import { MonoTypeOperatorFunction, TeardownLogic } from '../types'; |
| |
| /* tslint:disable:max-line-length */ |
| export function distinctUntilChanged<T>(compare?: (x: T, y: T) => boolean): MonoTypeOperatorFunction<T>; |
| export function distinctUntilChanged<T, K>(compare: (x: K, y: K) => boolean, keySelector: (x: T) => K): MonoTypeOperatorFunction<T>; |
| /* tslint:enable:max-line-length */ |
| |
| /** |
| * Returns an Observable that emits all items emitted by the source Observable that are distinct by comparison from the previous item. |
| * |
| * If a comparator function is provided, then it will be called for each item to test for whether or not that value should be emitted. |
| * |
| * If a comparator function is not provided, an equality check is used by default. |
| * |
| * ## Example |
| * A simple example with numbers |
| * ```ts |
| * import { of } from 'rxjs'; |
| * import { distinctUntilChanged } from 'rxjs/operators'; |
| * |
| * of(1, 1, 2, 2, 2, 1, 1, 2, 3, 3, 4).pipe( |
| * distinctUntilChanged(), |
| * ) |
| * .subscribe(x => console.log(x)); // 1, 2, 1, 2, 3, 4 |
| * ``` |
| * |
| * An example using a compare function |
| * ```typescript |
| * import { of } from 'rxjs'; |
| * import { distinctUntilChanged } from 'rxjs/operators'; |
| * |
| * interface Person { |
| * age: number, |
| * name: string |
| * } |
| * |
| * of<Person>( |
| * { age: 4, name: 'Foo'}, |
| * { age: 7, name: 'Bar'}, |
| * { age: 5, name: 'Foo'}, |
| * { age: 6, name: 'Foo'}, |
| * ).pipe( |
| * distinctUntilChanged((p: Person, q: Person) => p.name === q.name), |
| * ) |
| * .subscribe(x => console.log(x)); |
| * |
| * // displays: |
| * // { age: 4, name: 'Foo' } |
| * // { age: 7, name: 'Bar' } |
| * // { age: 5, name: 'Foo' } |
| * ``` |
| * |
| * @see {@link distinct} |
| * @see {@link distinctUntilKeyChanged} |
| * |
| * @param {function} [compare] Optional comparison function called to test if an item is distinct from the previous item in the source. |
| * @return {Observable} An Observable that emits items from the source Observable with distinct values. |
| * @method distinctUntilChanged |
| * @owner Observable |
| */ |
| export function distinctUntilChanged<T, K>(compare?: (x: K, y: K) => boolean, keySelector?: (x: T) => K): MonoTypeOperatorFunction<T> { |
| return (source: Observable<T>) => source.lift(new DistinctUntilChangedOperator<T, K>(compare, keySelector)); |
| } |
| |
| class DistinctUntilChangedOperator<T, K> implements Operator<T, T> { |
| constructor(private compare: (x: K, y: K) => boolean, |
| private keySelector: (x: T) => K) { |
| } |
| |
| call(subscriber: Subscriber<T>, source: any): TeardownLogic { |
| return source.subscribe(new DistinctUntilChangedSubscriber(subscriber, this.compare, this.keySelector)); |
| } |
| } |
| |
| /** |
| * We need this JSDoc comment for affecting ESDoc. |
| * @ignore |
| * @extends {Ignored} |
| */ |
| class DistinctUntilChangedSubscriber<T, K> extends Subscriber<T> { |
| private key: K; |
| private hasKey: boolean = false; |
| |
| constructor(destination: Subscriber<T>, |
| compare: (x: K, y: K) => boolean, |
| private keySelector: (x: T) => K) { |
| super(destination); |
| if (typeof compare === 'function') { |
| this.compare = compare; |
| } |
| } |
| |
| private compare(x: any, y: any): boolean { |
| return x === y; |
| } |
| |
| protected _next(value: T): void { |
| let key: any; |
| try { |
| const { keySelector } = this; |
| key = keySelector ? keySelector(value) : value; |
| } catch (err) { |
| return this.destination.error(err); |
| } |
| let result = false; |
| if (this.hasKey) { |
| try { |
| const { compare } = this; |
| result = compare(this.key, key); |
| } catch (err) { |
| return this.destination.error(err); |
| } |
| } else { |
| this.hasKey = true; |
| } |
| if (!result) { |
| this.key = key; |
| this.destination.next(value); |
| } |
| } |
| } |