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

src/operator/toPromise.ts

@@ -1,5 +1,5 @@
 import { Observable } from '../Observable';
-import { root } from '../util/root';
+import { toPromise as higherOrder } from '../operators/toPromise';
 
 /* tslint:disable:max-line-length */
 export function toPromise<T>(this: Observable<T>): Promise<T>;
@@ -56,20 +56,5 @@ export function toPromise<T>(this: Observable<T>, PromiseCtor: typeof Promise):
  * @owner Observable
  */
 export function toPromise<T>(this: Observable<T>, PromiseCtor?: typeof Promise): Promise<T> {
- if (!PromiseCtor) {
- if (root.Rx && root.Rx.config && root.Rx.config.Promise) {
- PromiseCtor = root.Rx.config.Promise;
- } else if (root.Promise) {
- PromiseCtor = root.Promise;
- }
- }
-
- if (!PromiseCtor) {
- throw new Error('no Promise impl found');
- }
-
- return new PromiseCtor((resolve, reject) => {
- let value: any;
- this.subscribe((x: T) => value = x, (err: any) => reject(err), () => resolve(value));
- });
+ return higherOrder(PromiseCtor)(this);
 }

src/operators/index.ts

@@ -72,6 +72,7 @@ export { timeout } from './timeout';
 export { timeoutWith } from './timeoutWith';
 export { timestamp } from './timestamp';
 export { toArray } from './toArray';
+export { toPromise } from './toPromise';
 export { window } from './window';
 export { windowCount } from './windowCount';
 export { windowTime } from './windowTime';

src/operators/toPromise.ts

@@ -0,0 +1,78 @@
+import { Observable } from '../Observable';
+import { root } from '../util/root';
+import { UnaryFunction } from '../interfaces';
+
+/* tslint:disable:max-line-length */
+export function toPromise<T>(): UnaryFunction<Observable<T>, Promise<T>>;
+export function toPromise<T>(PromiseCtor: typeof Promise): UnaryFunction<Observable<T>, Promise<T>>;
+/* tslint:enable:max-line-length */
+
+/**
+ * Converts an Observable sequence to a ES2015 compliant promise.
+ *
+ * @example
+ * // Using normal ES2015
+ * let source = Rx.Observable
+ * .of(42)
+ * .toPromise();
+ *
+ * source.then((value) => console.log('Value: %s', value));
+ * // => Value: 42
+ *
+ * // Rejected Promise
+ * // Using normal ES2015
+ * let source = Rx.Observable
+ * .throw(new Error('woops'))
+ * .toPromise();
+ *
+ * source
+ * .then((value) => console.log('Value: %s', value))
+ * .catch((err) => console.log('Error: %s', err));
+ * // => Error: Error: woops
+ *
+ * // Setting via the config
+ * Rx.config.Promise = RSVP.Promise;
+ *
+ * let source = Rx.Observable
+ * .of(42)
+ * .toPromise();
+ *
+ * source.then((value) => console.log('Value: %s', value));
+ * // => Value: 42
+ *
+ * // Setting via the method
+ * let source = Rx.Observable
+ * .of(42)
+ * .toPromise(RSVP.Promise);
+ *
+ * source.then((value) => console.log('Value: %s', value));
+ * // => Value: 42
+ *
+ * @param {PromiseConstructor} [PromiseCtor] The constructor of the promise. If not provided,
+ * it will look for a constructor first in Rx.config.Promise then fall back to
+ * the native Promise constructor if available.
+ * @return {Promise<T>} An ES2015 compatible promise with the last value from
+ * the observable sequence.
+ * @method toPromise
+ * @owner Observable
+ */
+export function toPromise<T>(PromiseCtor?: typeof Promise): UnaryFunction<Observable<T>, Promise<T>> {
+ return (source: Observable<T>) => {
+ if (!PromiseCtor) {
+ if (root.Rx && root.Rx.config && root.Rx.config.Promise) {
+ PromiseCtor = root.Rx.config.Promise;
+ } else if (root.Promise) {
+ PromiseCtor = root.Promise;
+ }
+ }
+
+ if (!PromiseCtor) {
+ throw new Error('no Promise impl found');
+ }
+
+ return new PromiseCtor((resolve, reject) => {
+ let value: any;
+ source.subscribe((x: T) => value = x, (err: any) => reject(err), () => resolve(value));
+ });
+ };
+}