feat(distinct): add higher-order lettable version of distinct

src/operator/distinct.ts

@@ -1,11 +1,5 @@
 import { Observable } from '../Observable';
-import { Operator } from '../Operator';
-import { Subscriber } from '../Subscriber';
-import { TeardownLogic } from '../Subscription';
-import { OuterSubscriber } from '../OuterSubscriber';
-import { InnerSubscriber } from '../InnerSubscriber';
-import { subscribeToResult } from '../util/subscribeToResult';
-import { ISet, Set } from '../util/Set';
+import { distinct as higherOrder } from '../operators';
 
 /**
  * Returns an Observable that emits all items emitted by the source Observable that are distinct by comparison from previous items.
@@ -55,70 +49,5 @@ import { ISet, Set } from '../util/Set';
 export function distinct<T, K>(this: Observable<T>,
  keySelector?: (value: T) => K,
  flushes?: Observable<any>): Observable<T> {
- return this.lift(new DistinctOperator(keySelector, flushes));
-}
-
-class DistinctOperator<T, K> implements Operator<T, T> {
- constructor(private keySelector: (value: T) => K, private flushes: Observable<any>) {
- }
-
- call(subscriber: Subscriber<T>, source: any): TeardownLogic {
- return source.subscribe(new DistinctSubscriber(subscriber, this.keySelector, this.flushes));
- }
-}
-
-/**
- * We need this JSDoc comment for affecting ESDoc.
- * @ignore
- * @extends {Ignored}
- */
-export class DistinctSubscriber<T, K> extends OuterSubscriber<T, T> {
- private values: ISet<K> = new Set<K>();
-
- constructor(destination: Subscriber<T>, private keySelector: (value: T) => K, flushes: Observable<any>) {
- super(destination);
-
- if (flushes) {
- this.add(subscribeToResult(this, flushes));
- }
- }
-
- notifyNext(outerValue: T, innerValue: T,
- outerIndex: number, innerIndex: number,
- innerSub: InnerSubscriber<T, T>): void {
- this.values.clear();
- }
-
- notifyError(error: any, innerSub: InnerSubscriber<T, T>): void {
- this._error(error);
- }
-
- protected _next(value: T): void {
- if (this.keySelector) {
- this._useKeySelector(value);
- } else {
- this._finalizeNext(value, value);
- }
- }
-
- private _useKeySelector(value: T): void {
- let key: K;
- const { destination } = this;
- try {
- key = this.keySelector(value);
- } catch (err) {
- destination.error(err);
- return;
- }
- this._finalizeNext(key, value);
- }
-
- private _finalizeNext(key: K|T, value: T) {
- const { values } = this;
- if (!values.has(<K>key)) {
- values.add(<K>key);
- this.destination.next(value);
- }
- }
-
+ return higherOrder(keySelector, flushes)(this);
 }

src/operators/distinct.ts

@@ -0,0 +1,124 @@
+import { Observable } from '../Observable';
+import { Operator } from '../Operator';
+import { Subscriber } from '../Subscriber';
+import { TeardownLogic } from '../Subscription';
+import { OuterSubscriber } from '../OuterSubscriber';
+import { InnerSubscriber } from '../InnerSubscriber';
+import { subscribeToResult } from '../util/subscribeToResult';
+import { ISet, Set } from '../util/Set';
+import { MonoTypeOperatorFunction } from '../interfaces';
+
+/**
+ * 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 function distinct<T, K>(keySelector?: (value: T) => K,
+ flushes?: Observable<any>): MonoTypeOperatorFunction<T> {
+ return (source: Observable<T>) => source.lift(new DistinctOperator(keySelector, flushes));
+}
+
+class DistinctOperator<T, K> implements Operator<T, T> {
+ constructor(private keySelector: (value: T) => K, private flushes: Observable<any>) {
+ }
+
+ call(subscriber: Subscriber<T>, source: any): TeardownLogic {
+ return source.subscribe(new DistinctSubscriber(subscriber, this.keySelector, this.flushes));
+ }
+}
+
+/**
+ * We need this JSDoc comment for affecting ESDoc.
+ * @ignore
+ * @extends {Ignored}
+ */
+export class DistinctSubscriber<T, K> extends OuterSubscriber<T, T> {
+ private values: ISet<K> = new Set<K>();
+
+ constructor(destination: Subscriber<T>, private keySelector: (value: T) => K, flushes: Observable<any>) {
+ super(destination);
+
+ if (flushes) {
+ this.add(subscribeToResult(this, flushes));
+ }
+ }
+
+ notifyNext(outerValue: T, innerValue: T,
+ outerIndex: number, innerIndex: number,
+ innerSub: InnerSubscriber<T, T>): void {
+ this.values.clear();
+ }
+
+ notifyError(error: any, innerSub: InnerSubscriber<T, T>): void {
+ this._error(error);
+ }
+
+ protected _next(value: T): void {
+ if (this.keySelector) {
+ this._useKeySelector(value);
+ } else {
+ this._finalizeNext(value, value);
+ }
+ }
+
+ private _useKeySelector(value: T): void {
+ let key: K;
+ const { destination } = this;
+ try {
+ key = this.keySelector(value);
+ } catch (err) {
+ destination.error(err);
+ return;
+ }
+ this._finalizeNext(key, value);
+ }
+
+ private _finalizeNext(key: K|T, value: T) {
+ const { values } = this;
+ if (!values.has(<K>key)) {
+ values.add(<K>key);
+ this.destination.next(value);
+ }
+ }
+
+}

src/operators/index.ts

@@ -19,6 +19,7 @@ export { defaultIfEmpty } from './defaultIfEmpty';
 export { delay } from './delay';
 export { delayWhen } from './delayWhen';
 export { dematerialize } from './dematerialize';
+export { distinct } from './distinct';
 export { distinctUntilChanged } from './distinctUntilChanged';
 export { distinctUntilKeyChanged } from './distinctUntilKeyChanged';
 export { elementAt } from './elementAt';