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